methimazole and Cat-Diseases

Pharmacological management of feline hyperthyroidism offers a practical treatment option for many hyperthyroid cats. Two drugs have been licensed for cats in the last decade: methimazole and its pro-drug carbimazole. On the basis of current evidence and available tablet sizes, starting doses of 2·5 mg methimazole twice a day and 10 to 15 mg once a day for the sustained release formulation of carbimazole are recommended. These doses should then be titrated to effect in order to obtain circulating total thyroxine (TT4) concentrations in the lower half of the reference interval. Treated cases should be monitored for side-effects, especially during the first months of treatment. Some side-effects may require discontinuation of treatment. At each monitoring visit, clinical condition and quality of life should also be evaluated, with special attention to possible development of azotaemia, hypertension and iatrogenic hypothyroidism. When euthyroidism has been achieved, monitoring visits are recommended after 1 month, 3 months and biannually thereafter. Cats with pre-existing azotaemia have shorter survival times. However, development of mild azotaemia during the initial course of treatment, unless associated with hypothyroidism, does not appear to decrease survival time. The long-term effects of chronic medical management require further study.

Topics: Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Hyperthyroidism; Methimazole; Veterinary Medicine

Radioiodine is considered the treatment of choice for hyperthyroidism, but in some situations, methimazole therapy is preferred, such as in cats with preexisting renal insufficiency. Unfavorable outcomes from methimazole are usually attributable to side effects, such as gastrointestinal upset, facial excoriation, thrombocytopenia, neutropenia, or liver enzyme elevations. Because restoration of euthyroidism can lead to a drop in glomerular filtration rate, all cats treated with methimazole should be monitored with blood urea nitrogen and creatinine levels in addition to serum thyroxine (T(4)) and a complete blood cell count. Transdermal methimazole is associated with fewer gastrointestinal side effects and can be used in cats with simple vomiting or inappetence from oral methimazole. Hypertension may not resolve immediately when serum T(4) is normalized, and moderate to severe hypertension should be treated concurrently with atenolol, amlodipine, or an angiotensin-converting enzyme inhibitor.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Hyperthyroidism; Methimazole

Radioiodine is considered the treatment of choice for hyperthyroidism, but in some situations, methimazole therapy is preferred, such as in cats with pre-existing renal insufficiency. Methimazole blocks thyroid hormone synthesis, and controls hyperthyroidism in more than 90% of cats that tolerate the drug. Unfavorable outcomes are usually due to side effects such as gastrointestinal (GI) upset, facial excoriation, thrombocytopenia, neutropenia, or liver enzyme elevations; warfarin-like coagulopathy or myasthenia gravis have been reported but are rare. Because restoration of euthyroidism can lead to a drop in glomerular filtration rate, all cats treated with methimazole should be monitored with BUN and creatinine, in addition to serum T4, complete blood count, and liver enzymes. Transdermal methimazole is associated with fewer GI side effects, and can be used in cats with simple vomiting or inappetance from oral methimazole. Hypertension may not resolve immediately when serum T4 is normalized, and moderate to severe hypertension should be treated concurrently with-atenolol, amlodipine, or an ACE inhibitor. Alternatives to methimazole include carbimazole, propylthiouracil, or iodinated contrast agents.

Topics: Adrenergic beta-Antagonists; Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Contrast Media; Hyperthyroidism; Iodine Radioisotopes; Iodobenzenes; Methimazole; Propylthiouracil; Treatment Outcome

Drug therapy for the endocrine system is implemented to replace a hormone deficiency or to prevent or reduce the formation or effects of excess hormone. Treatment of endocrine disorders covers diseases of the pituitary, adrenal, parathyroid, and thyroid glands as well as the endocrine pancreas. This article focuses on new therapies currently available for specific diseases. Administration of trilostane for treatment of hyperadrenocorticism and use of insulin glargine, protamine zinc insulin (PZI), and porcine Lente insulin for diabetes mellitus are discussed. In addition, transdermal methimazole therapy for treatment of feline hyperthyroidism and administration of progestins for pituitary dwarfism are considered.

Topics: Adrenocortical Hyperfunction; Animals; Antithyroid Agents; Cat Diseases; Cats; Diabetes Mellitus; Dihydrotestosterone; Dog Diseases; Dogs; Enzyme Inhibitors; Hyperthyroidism; Hypoglycemic Agents; Insulin, Long-Acting; Methimazole

Topics: Animals; Cat Diseases; Cats; Clinical Enzyme Tests; Female; Hyperthyroidism; Iodine Radioisotopes; Male; Methimazole; Propylthiouracil; Thyroid Hormones; Thyroid Neoplasms; Thyroidectomy

Hyperthyroidism is a common endocrinopathy of middle-aged and elderly cats. Dietary treatment has been proposed as an alternative to traditional therapies.. The aim of this prospective study was to compare the efficacy of iodine-restricted food versus pharmacological therapy with methimazole in client-owned cats with hyperthyroidism.. Indoor cats with newly diagnosed hyperthyroidism (consistent clinical signs and serum total thyroxine concentration greater than 50 nmol/l) were assigned to one of three groups: (A) received an iodine-restricted food as a single therapy; (B) received transdermal methimazole in pluronic lecithin organogel; and (C) received oral methimazole. In all groups, clinical parameters, biochemistry, and serum total thyroxine were evaluated at baseline and 10, 30, 60, and 90 days after treatment began.. Thirty-four cats were enrolled in the study (group A:. These results suggest that iodine-restricted food is effective at reducing the total thyroxine concentration in the serum of hyperthyroid cats. Moreover, the iodine-restricted food did not cause any increase in serum creatinine concentrations and failed to improve liver enzymes abnormalities. These findings could indicate a persistent hyperthyroid state in cats treated with iodine-restricted food despite normalization of serum total thyroxine concentrations.

Topics: Administration, Cutaneous; Administration, Oral; Animals; Antithyroid Agents; Cat Diseases; Cats; Female; Hyperthyroidism; Iodine; Male; Methimazole; Non-Randomized Controlled Trials as Topic; Prospective Studies; Thyroxine

Feline hyperthyroidism is a common endocrine disorder in older cats for which homeopathic treatment has been advocated. A double-blinded, placebo-controlled randomised trial was performed to look for evidence of efficacy for the use of individualised homeopathy in the treatment of this disease. Using a case definition of a concentration of the thyroid hormone T4 >66 nmol/l, cats were randomised into two treatment arms. Either a placebo or a homeopathic treatment was given to each cat blindly. After 21 days, the T4 levels, weight (Wt) and heart rate (HR) were compared with pretreatment values. There were no statistically significant differences in the changes seen between the two treatment arms following placebo or homeopathic treatment (T4 P=0.96, Wt P=0.16, HR P=0.36) or between the means of each parameter for either treatment arm before and after placebo or homeopathic treatment (all P values >0.13). In a second phase of the study, patients in both treatment arms were given methimazole treatment for 21 days and T4, Wt and HR determined again. Again there were no statistically significant differences between the groups, but there were statistically significant reductions in T4 (P<0.0001) and HR (P=0.02), and a statistically significant increase in Wt (P=0.004) in both groups compared with their pre-methimazole treatment levels. The results of this study failed to provide any evidence of the efficacy of homeopathic treatment of feline hyperthyroidism.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Double-Blind Method; Homeopathy; Hyperthyroidism; Methimazole; Thyroxine; Treatment Outcome

To determine whether once daily administration of methimazole was as effective and safe as twice daily administration in cats with hyperthyroidism.. Randomized, nonblinded, clinical trial.. 40 cats with newly diagnosed hyperthyroidism.. Cats were randomly assigned to receive 5 mg of methimazole, PO, once daily (n = 25) or 2.5 mg of methimazole, PO, twice daily (15). A complete physical examination, including measurement of body weight; CBC; serum biochemical analyses, including measurement of serum thyroxine concentration; and urinalysis were performed, and blood pressure was measured before and 2 and 4 weeks after initiation of treatment.. Serum thyroxine concentration was significantly higher in cats given methimazole once daily, compared with cats given methimazole twice daily, 2 weeks (3.7 vs 2.0 micro +/- g/dL) and 4 weeks (3.2 vs 1.7 microg/dL) after initiation of treatment. In addition, the proportion of cats that were euthyroid after 2 weeks of treatment was lower for cats receiving methimazole once daily (54%) than for cats receiving methimazole twice daily (87%). Percentages of cats with adverse effects (primarily gastrointestinal tract upset and facial pruritus) were not significantly different between groups.. Results suggest that once daily administration of methimazole was not as effective as twice daily administration in cats with hyperthyroidism and cannot be recommended for routine use.

Topics: Administration, Oral; Animals; Antithyroid Agents; Cat Diseases; Cats; Drug Administration Schedule; Hyperthyroidism; Methimazole; Safety; Thyroxine; Treatment Outcome

To determine whether increases in BUN and serum creatinine (SCr) concentrations, which have been reported to develop after surgical bilateral thyroidectomy in hyperthyroid cats, also develop after treatment of hyperthyroidism with radioactive iodine and methimazole.. Prospective, clinical trial.. 58 hyperthyroid cats.. Urine specific gravity, SCr, BUN, and serum thyroxine (T4) concentrations were determined before and 30 and 90 days after treatment of hyperthyroidism with radioactive iodine, methimazole, or surgical bilateral thyroidectomy.. Mean SCr and BUN concentrations determined 30 and 90 days after treatment were significantly higher than those measured before treatment. Mean SCr, BUN, and T4 concentrations were not different among groups before treatment or 30 and 90 days after treatment.. Reduction of serum T4 concentrations after treatment of hyperthyroidism may result in azotemia in older cats with chronic renal disease. Treating azotemic hyperthyroid cats with methimazole until it can be determined whether correction of the hyperthyroid state will exacerbate the azotemia may be prudent.

Topics: Animals; Antithyroid Agents; Blood Urea Nitrogen; Cat Diseases; Cats; Creatinine; Hyperthyroidism; Iodine Radioisotopes; Kidney; Methimazole; Prospective Studies; Specific Gravity; Thyroidectomy; Thyroxine; Urine

The objective of this study was to evaluate the presence of traces of thiamazole in the urine of owners of hyperthyroid cats treated with antithyroid drugs.. Urine was collected from 24 owners of hyperthyroid cats, five human patients treated with thiamazole and five healthy humans without any contact with antithyroid drugs. All owners of hyperthyroid cats were asked to fill out a questionnaire. Urine of hyperthyroid cats was collected by spontaneous micturition. All urine samples were stored at -20°C until analysis by ultra-high-performance liquid chromatography coupled to high-resolution quadrupole Orbitrap mass spectrometry.. These owners were assessed to have a lot of contact with their cat. Adherence to antithyroid medication handling guidelines was rather poor. High concentrations of thiamazole were detected in all feline samples (median concentration 2818 ng/ml; range 104-15,127) and in the urine of all human patients treated with thiamazole (median concentration 4153 ng/ml; range 1826-5009). No thiamazole was detected in the urine of owners of hyperthyroid cats (limit of detection 3.88 ng/ml; limit of quantification 11.75 ng/ml).. The results regarding the potential exposure of owners of hyperthyroid cats to antithyroid drugs are reassuring. Nevertheless, prudence is still warranted when administering antithyroid drugs. Whether these results can be extrapolated to the use of transdermal application requires further investigation.

Topics: Administration, Cutaneous; Animals; Antithyroid Agents; Cat Diseases; Cats; Humans; Hyperthyroidism; Methimazole; Surveys and Questionnaires

Acquired myasthenia gravis (AMG) is increasingly recognized in cats, yet information regarding the natural history of the disease, treatment, and outcome including occurrence of immune and spontaneous remission remains limited.. To determine the long-term outcome of cats with AMG without evidence of a cranial mediastinal mass (CMM).. Eight cats diagnosed with AMG without evidence of a CMM.. Retrospective case series. The medical records of cats diagnosed with AMG between 2005 and 2018 from 2 veterinary referral hospitals were reviewed for inclusion. Inclusion criteria consisted of a diagnosis of AMG, thoracic imaging, serum biochemistry including measurement of creatine kinase, and a CBC. Exclusion criteria were the presence of an identifiable CMM, or administration of methimazole or carbimazole.. All cats had an excellent long-term outcome, achieving immune remission within 6 months of diagnosis, including 4 cats that did not receive any treatment and whose natural course of disease involved spontaneous remission. Clinical presentation was heterogeneous, and skeletal muscle weakness and fatigability induced or exacerbated by the wheelbarrow exercise stress test were the most consistent abnormalities associated with AMG.. Cats diagnosed with AMG without evidence a CMM have a favorable outcome and frequently achieve immune remission. Moreover, the natural history of AMG in cats includes spontaneous remission when there is no evidence of a CMM. Attempting to rule out the presence of a CMM therefore refines prognosis, and treatment is not always necessary in this disease population.

Topics: Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Female; Male; Methimazole; Myasthenia Gravis; Remission, Spontaneous; Retrospective Studies

Objectives The aim of this study was to evaluate changes in circulating insulin-like growth factor type 1 (IGF-1) concentrations in hyperthyroid cats, before and after thiamazole treatment. Methods Thirty-four hyperthyroid cats were retrospectively included. Plasma free thyroxine (fT4) and IGF-1 concentrations were measured at diagnosis and 3 months after initiating antithyroid drug therapy. Results Median fT4 significantly decreased ( P <0.001) after treatment (from 78 pmol/l [range 43-122 pmol/l] to 31 pmol/l [range below assay limit of detection to 88 pmol/l]), whereas IGF-1 values significantly increased ( P <0.001) after treatment (from 117 ng/ml [33-341 ng/ml] to 221 ng/ml [36-865 ng/ml]). fT4 and IGF-1 concentrations were significantly negatively correlated both at diagnosis (r = -0.43, P = 0.01) and after treatment (r = -0.51, P = 0.002). Conclusions and relevance In cats, IGF-1 concentrations appear to be inversely proportional to the severity of hyperthyroidism and significantly increase after treatment with thiamazole.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Female; Hyperthyroidism; Insulin-Like Growth Factor I; Male; Methimazole

Hyperthyroidism is the most common feline endocrinopathy; thyroid computed tomography (CT) may improve disease detection and methimazole dose selection. Objectives of this experimental pre-post with historical case-control study were to perform thyroid CT imaging in awake or mildly sedated hyperthyroid cats, compare thyroid gland CT appearance in euthyroid and hyperthyroid cats pre- and postmethimazole treatment, and determine whether thyroid size or attenuation correlate with methimazole dose needed for euthyroidism. Premethimazole treatment, eight hyperthyroid cats received CT scans from the head to heart, which were compared to CT of seven euthyroid cats. Total thyroxine levels were monitored every 3-4 weeks. Postmethimazole CT was performed 30 days after achieving euthyroid status. Computed tomography parameters recorded included thyroid length, width, height, attenuation, and heterogeneity. Median time between CT was 70 days (53-213 days). Mild sedation was needed in five hyperthyroid cats premethimazole, and none postmethimazole. Thyroid volume was significantly larger in hyperthyroid cats compared to euthyroid cats (785.0 mm

Topics: Animals; Antithyroid Agents; Case-Control Studies; Cat Diseases; Cats; Female; Hyperthyroidism; Male; Methimazole; Tomography, X-Ray Computed

Hyperthyroidism is common in cats, but there are no reports that evaluate its severity or underlying thyroid tumor disease based on disease duration (ie, time from original diagnosis). The objective of this study was to compare serum thyroxine (T4) concentrations and thyroid scintigraphic characteristics of cats referred for radioiodine treatment based on disease duration.. This was a cross-sectional study of 2096 cats with hyperthyroidism. Cats were divided into five groups based on time from diagnosis: ⩽1 year (n = 1773); >1-2 years (n = 169); >2-3 years (n = 88); >3-4 years (n = 35); and >4-6.1 years (n = 31). Methimazole, administered to 996 (47.5%) cats, was stopped at least 1 week prior to examination to allow for serum T4 testing. Each thyroid scintiscan was evaluated for pattern (unilateral, bilateral, multifocal), location (cervical, thoracic inlet, chest) and size (small, medium, large, huge) of the thyroid tumor, as well as features suggesting malignancy.. Median serum T4 concentration increased with increasing disease duration from 100 nmol/l (⩽1 year) to 315 nmol/l (>4-6.1 years) (P <0.001). Prevalence of unilateral thyroid disease decreased, whereas multifocal disease (three or more tumor nodules) increased (P <0.001) with increasing disease duration. Median tumor volume in the five groups increased from 1.6 cm(3) (⩽1 year) to 6.4 cm(3) (>4-6.1 years). Prevalence of large (4-8 cm(3)) and huge (>8 cm(3)) thyroid tumors increased from 5.1% (⩽1 year) to 88.6% (>4-6.1 years), while the prevalence of intrathoracic tumor tissue increased from 3.4% (⩽1 year) to 32.3% (>4-6.1 years). Prevalence of suspected thyroid carcinoma (characterized by severe hyperthyroidism; huge, intrathoracic, multifocal tumors; refractory to methimazole treatment) increased with increasing disease duration from 0.4% (⩽1 year) to 19.3% (>4-6.1 years).. Our results indicate that the prevalence of severe hyperthyroidism, large thyroid tumors, multifocal disease, intrathoracic thyroid masses and suspected malignant disease all increase with disease duration in cats referred for radioiodine therapy.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Cross-Sectional Studies; Hyperthyroidism; Iodine Radioisotopes; Methimazole; Prevalence; Thyroid Function Tests

Thyroid scintigraphy is commonly used for evaluation of cats with hyperthyroidism, with the thyroid-to-salivary ratio (T/S) being the most common method to quantify the degree of thyroid activity and disease. Calculation of thyroid-to-background ratios (T/B) or percent thyroidal uptake of (99m) TcO(-) 4 (TcTU) has only been reported in a few studies. The purpose of this prospective, cross-sectional study was to evaluate a number of quantitative scintigraphic indices as diagnostic tests for hyperthyroidism, including the T/S, three different T/B, TcTU, and estimated thyroid volume. Of 524 cats referred to our clinic for evaluation of suspected hyperthyroidism, the diagnosis was confirmed (n = 504) or excluded (n = 20) based on results of a serum thyroid panel consisting of thyroxine (T4 ), triiodothyronine (T3 ), free T4 (fT4 ), and thyroid-stimulating hormone (TSH) concentrations. In the hyperthyroid cats, median values for TcTU, T/S, and three T/B ratios were all significantly higher (P < 0.001) than values in euthyroid suspect cats or clinically normal cats. All scintigraphic parameters were relatively sensitive and specific as diagnostic tests for hyperthyroidism, but the T/S ratio had the highest test accuracy. The T/S ratio correlated strongly with the TcTU (r = 0.85). However, the TcTU had a higher and more significant correlation (P < 0.01) with serum T4 (r = 0.76 vs. 0.64), T3 (r = 0.77 vs. 0.64), and estimated thyroid volume (r = 0.62 vs. 0.38). Overall, calculation of TcTU is an accurate diagnostic test, but also appears to be the best parameter to predict the functional volume and metabolic activity of the feline adenomatous thyroid gland.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Female; Hyperthyroidism; Male; Methimazole; Radionuclide Imaging; Saliva; Sodium Pertechnetate Tc 99m; Thyroid Gland

Topics: Animals; Antithyroid Agents; Arrhythmias, Cardiac; Cat Diseases; Cats; Electrocardiography; Female; Hyperthyroidism; Methimazole; Pacemaker, Artificial

The aim of the study was to determine if methimazole applied in a transdermal formulation to the internal pinna will cross to the external pinna in an in vitro Franz cell model.. The ears from six cats were harvested soon after death. Whole ears were mounted onto Franz-type diffusion cells with the stratum corneum of the inner pinnae uppermost. A commercial transdermal preparation containing methimazole (0.1 ml/10 mg) was applied to the inner pinnae. At 1, 2, 4, 6, 8, 12, 18, 24 and 30 h, a 200 µl sample of reservoir solution was removed to determine the methimazole concentration by high-performance liquid chromatography. The ears were then dissected, separating the internal pinna from the cartilage and the external pinna, before the methimazole concentration was measured at each site. The thickness of the different regions of the ear was measured on paraffin histology sections.. Mean ± SD methimazole concentrations at 30 h for the right and left ear, respectively, were: inner ear, 1.25 ± 0.53 mg/g, 0.39 ± 0.26 mg/g; cartilage, 1.36 ± 0.47 mg/g, 0.33 ± 0.20 mg/g; and outer ear, 1.0 ± 0.32 mg/g, 0.33 ± 0.14 mg/g. There was a difference between the left and right ears (P <0.001). Minimal methimazole concentrations were detected in the receptor fluid. The mean methimazole concentration absorbed by the skin after application of 10 mg was, for the right ear, 3.65 ± 1.27 mg/g and, for the left, 1.08 ± 0.27 mg/g. There was no correlation between methimazole concentrations and thickness of each region of the ear.. Methimazole in a lipophilic vehicle applied to the inner pinna will penetrate to the outer pinna of cats in an in vitro model, which may have safety implications for humans associated with cats treated with transdermal methimazole. Substantial inter-individual variation was found. Further research is required in the area of transdermal penetration of drugs in cats.

Topics: Administration, Cutaneous; Animals; Antithyroid Agents; Biomechanical Phenomena; Cat Diseases; Cats; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Ear Auricle; Ear, External; Methimazole

An 11-year-old spayed female domestic shorthair cat was presented for polydipsia, hyperactivity and bilateral thyroid gland enlargement. Total T4 (TT4) was in the upper interval range; therefore, an early hyperthyroidism was suspected. A treatment trial with methimazole was started, as the owner refused further tests. Six months later the owner stopped the treatment. One year later, clinical signs persisted and TT4 was still in the upper interval range. Methimazole was re-introduced but 48 h later the cat presented non-pruritic alopecia with erythema, scales and perilesional yellowish crusts. Pyogranulomatous mural folliculitis was diagnosed by histopatological examination of the skin biopsies. Methimazole was withdrawn and macroscopic lesions healed and disappeared histologically in 15 days. An idiosyncratic drug reaction to methimazole was suspected. To the best of our knowledge, this is the first report of feline pyogranulomatous mural folliculitis likely secondary to an adverse drug reaction to methimazole administration.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Female; Folliculitis; Hyperthyroidism; Methimazole; Thyroid Function Tests

Transdermal methimazole is suggested as an alternative to oral therapy for hyperthyroid cats that are difficult to pill. However, no information on long-term management with this treatment is available. Our objective was therefore to retrospectively evaluate the efficacy and safety of long-term transdermal methimazole treatment in hyperthyroid cats. Sixty cats with newly diagnosed hyperthyroidism and available long-term follow-up information were included. Methimazole was formulated in a pluronic lecithin organogel-based vehicle and was applied to the pinna of the inner ear. Cats were re-evaluated at regular intervals. Median (range) follow-up was 22.6 months (3.6-88.4 months). Clinical improvement was observed in all cats and side effects were rare (mild transient gastrointestinal signs: n = 3; erythema of the pinna: n = 2, necessitating a switch to oral medication). Despite a significant decrease, with median T4 concentrations within the reference interval during the follow-up period, several cats repeatedly had T4 concentrations in the thyrotoxic and hypothyroid range. Maximal and minimal daily doses during the follow-up period were 15.0 and 1.0 mg, respectively; they were significantly higher than the starting dose after 24-36 months of therapy. Although the majority of owners were highly satisfied with the treatment, several admitted not treating their cat regularly. Transdermal methimazole is a safe option for the long-term management of feline hyperthyroidism. However, it seems difficult to keep the T4 concentrations constantly within the reference interval. Higher doses can be expected after prolonged treatment and, despite the convenience of transdermal application, owner compliance should be assessed regularly.

Topics: Administration, Cutaneous; Animals; Antithyroid Agents; Cat Diseases; Cats; Ear Auricle; Female; Follow-Up Studies; Hyperthyroidism; Male; Methimazole; Retrospective Studies; Treatment Outcome

Topics: Animals; Antithyroid Agents; Arrhythmias, Cardiac; Cat Diseases; Cats; Electrocardiography; Hyperthyroidism; Methimazole

Hyperthyroidism is the most common feline endocrinopathy. Treatment options comprise anti-thyroid medication, iodine-restricted diet, surgical thyroidectomy and radioiodine. One hundred and eleven owners of hyperthyroid cats completed a detailed survey asking about their experiences and views on the management of hyperthyroidism. Male cats were slightly over-represented (60 cats, 54%). Concurrent chronic kidney disease was reported in 27% of the cats. Oral anti-thyroid medication was offered to 92% of owners. The final treatment decision was usually based on the veterinarian's recommendation or joint decision-making between the owner and the veterinarian. Almost all of the cats (103, 93%) had received oral anti-thyroid medication at some point in the course of their disease. Sixty-nine cats (62%) were receiving oral anti-thyroid medication at the time of survey completion. Management of hyperthyroidism using UK veterinary-licensed oral anti-thyroid medication (Vidalta; MSD Animal Health, Felimazole; Dechra Veterinary Products) was associated with 72-75% success rates in terms of owner-assessed clinical outcome. The most important treatment priorities for owners were the prescription of the most accurate dose of medication and use of the lowest possible dose. None ranked once-daily treatment as most important to them, and 79% of owners said that they were, or would be, happy to dose their cat twice daily to control its hyperthyroidism. For 62% of owners, pilling their cat twice daily was not a problem. These results suggest that most cat owners are not a barrier to prescribing twice-daily anti-thyroid medication, if required.

Topics: Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Data Collection; Female; Hyperthyroidism; Male; Methimazole; Ownership

Thyroid hormones have many effects on cardiovascular function, and deficiency or excess of thyroid hormones can result in cardiac dysfunction. Abnormalities of the cardiovascular system are often identified during examination of hyperthyroid and hypothyroid patients. This article addresses the effects of thyroid hormones on the cardiovascular system and the clinical relevance of the cardiovascular response to thyroid dysfunction. In addition, treatment recommendations are presented.

Topics: Animals; Antithyroid Agents; Cardiovascular Diseases; Cat Diseases; Cats; Dog Diseases; Dogs; Hyperthyroidism; Hypothyroidism; Methimazole; Thyroxine

Topics: Animals; Antithyroid Agents; Arrhythmias, Cardiac; Cat Diseases; Cats; Electrocardiography; Female; Hyperthyroidism; Methimazole

A 12-year-old neutered male domestic shorthair cat presented for chronic, localized, swelling and crusting of the left upper lip, weight loss, sporadic vomiting, and focal alopecia between the scapulae was diagnosed with hyperthyroidism and regional eosinophilic lymphadenitis. Treatment with methimazole exacerbated an underlying hypersensitivity disorder leading to marked generalized lymphadenopathy that histologically mimicked lymphoma.

Topics: Animals; Cat Diseases; Cats; Hyperthyroidism; Lymphatic Diseases; Male; Methimazole; Pruritus

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Female; Hyperthyroidism; Leptin; Male; Methimazole; Thyroid Hormones; Thyroxine; Treatment Outcome

A 12-year-old female neutered ragdoll crossbred cat was presented for investigation of generalised weakness and regurgitation. The cat was being treated with transdermal methimazole for hyper-thyroidism, which had been diagnosed 10 weeks previously. An acetylcholine receptor antibody titre was consistent with acquired myasthenia gravis. Withdrawal of methimazole and treatment with pyridostigmine was followed by resolution of clinical signs and reduction of the acetylcholine -receptor antibody titre. Medical control of hyperthyroidism was subsequently achieved with carbimazole, administered in conjunction with pyridostigmine, and no recurrence of clinical signs was observed. Myasthenia gravis is an uncommon but clinically significant adverse effect of methimazole therapy in cats, and may be caused by immunomodulatory properties of this drug. An adverse drug reaction should be considered in cats receiving methimazole that develop myasthenia gravis, and potentially also other immune-mediated disorders.

Topics: Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Female; Hyperthyroidism; Methimazole; Myasthenia Gravis; Pyridostigmine Bromide; Receptors, Cholinergic

To assess the influence of thyroid function on natriuretic peptide concentration in hyperthyroid cats before and after treatment.. Serum natriuretic peptide concentration was measured in 61 hyperthyroid cats recruited from first-opinion clinics before and after treatment.. Following successful treatment, total thyroxine, heart rate, systolic blood pressure and packed cell volume all decreased and bodyweight and creatinine concentrations increased. Furthermore, a significant (P < 0·001) decline in NT-proBNP concentration but not NT-proANP was identified.. Thyroid function has a modest but significant effect on NT-proBNP concentration. Thyroid status should be taken into account when interpreting NT-proBNP concentrations in cats.

Topics: Animals; Antithyroid Agents; Biomarkers; Blood Pressure; Case-Control Studies; Cat Diseases; Cats; Female; Heart Rate; Hyperthyroidism; Male; Methimazole; Natriuretic Peptide, Brain; Natriuretic Peptides; Peptide Fragments; Thyroxine; Treatment Outcome

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Combined Modality Therapy; Hyperthyroidism; Iodine Radioisotopes; Methimazole; Prognosis

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Hyperthyroidism; Lymphatic Diseases; Methimazole

Topics: Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Diagnosis, Differential; Hyperthyroidism; Lymphatic Diseases; Methimazole

A nine-year-old, domestic shorthair cat was diagnosed with hyperthyroidism and treated with methimazole, which resulted in lethargy, inappetence and marked generalised lymphadenomegaly within two weeks of initiation of therapy. Cytology, histopathology and immunohistochemistry were suggestive of atypical lymphoid hyperplasia. Cessation of treatment resulted in resolution of all clinical signs and physical abnormalities within two days. Subsequent treatment with radioactive iodine cured this cat of its hyperthyroidism. The lymphadenomegaly did not return at any stage and the cat is currently asymptomatic. Although methimazole administration for feline hyperthyroidism has been associated with many side effects, lymphadenomegaly has, to the authors' knowledge, not been previously reported.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Diagnosis, Differential; Hyperthyroidism; Lymphatic Diseases; Male; Methimazole

To compare survival times for cats with hyperthyroidism treated with iodine 131, methimazole, or both and identify factors associated with survival time.. Retrospective case series.. 167 cats.. Medical records of cats in which hyperthyroidism had been confirmed on the basis of high serum thyroxine concentration, results of thyroid scintigraphy, or both were reviewed.. 55 (33%) cats were treated with 131I alone, 65 (39%) were treated with methimazole followed by 131I, and 47 (28%) were treated with methimazole alone. Twenty-four of 166 (14%) cats had preexisting renal disease, and 115 (69%) had preexisting hepatic disease. Age was positively correlated (r = 0.4) with survival time, with older cats more likely to live longer. Cats with preexisting renal disease had significantly shorter survival times than did cats without preexisting renal disease. When cats with preexisting renal disease were excluded, median survival time for cats treated with methimazole alone (2.0 years; interquartile range [IQR], 1 to 3.9 years) was significantly shorter than median survival time for cats treated with 131I alone (4.0 years; IQR, 3.0 to 4.8 years) or methimazole followed by 131I (5.3 years; IQR, 2.2 to 6.5 years).. Results suggest that age, preexisting renal disease, and treatment type were associated with survival time in cats undergoing medical treatment of hyperthyroidism.

Topics: Age Factors; Animals; Antithyroid Agents; Cat Diseases; Cats; Drug Therapy, Combination; Female; Hyperthyroidism; Iodine Radioisotopes; Kidney Diseases; Male; Methimazole; Retrospective Studies; Survival Rate; Treatment Outcome

Thirteen cats, newly diagnosed with hyperthyroidism, were treated with a transdermal formulation of methimazole at a dose of 5 mg (0.1 mL) (concentration of 50 mg/mL) applied to the internal ear pinna every 12 h for 28 d. Baseline hematologic and biochemical values, along with serum thyroxine (T4) levels, were obtained on presentation (day 0). Cats were evaluated at 14 d (D14) and 28 d (D28) following transdermal therapy. At each visit, a physical examination, a complete blood cell count, a serum biochemical analysis, and a serum T4 evaluation were performed. Ten cats completed the study. Clinical improvement, as well as a significant decrease in T4, was noted in all cats. Serum T4 measured at D14 and D28 were significantly lower at 27.44 nmol/L, s = 37.51 and 14.63 nmol/L, s = 10.65, respectively (P < 0.0001), as compared with values at D0 (97.31 nmol/L, s = 37.55). Only 1 cat showed a cutaneous adverse reaction along with a marked thrombocytopenia. The results of this prospective clinical study suggest that transdermal methimazole is an effective and safe alternative to conventional oral formulations.

Topics: Administration, Cutaneous; Animals; Antithyroid Agents; Blood Cell Count; Blood Chemical Analysis; Cat Diseases; Cats; Female; Hyperthyroidism; Male; Methimazole; Prospective Studies; Safety; Thyroxine; Treatment Outcome

Hyperthyroidism and chronic renal disease occur commonly in geriatric cats, often in association with potentially life-threatening primary or secondary hypertension. Early treatment of hypertension minimizes damage to vital organs. This case illustrates the complexity of managing hypertension in a geriatric cat with both hyperthyroidism and renal disease.

Topics: Animals; Antihypertensive Agents; Antithyroid Agents; Cat Diseases; Cats; Diagnosis, Differential; Enalapril; Female; Hypertension; Hyperthyroidism; Kidney Diseases; Methimazole; Treatment Outcome

The objectives of this study were to assess serum thyroxine concentrations and clinical response in hyperthyroid cats to treatment with transdermal methimazole, and to determine if further investigation is indicated. Clinical and laboratory data from 13 cats with hyperthyroidism were retrospectively evaluated. Methimazole (Tapazole, Eli Lilly) was formulated in a pleuronic lecithin organogel (PLO)-based vehicle and was applied to the inner pinna of the ear at a dosage ranging from 2.5mg/cat q 24h to 10.0mg/cat q 12h. During the treatment period, cats were re-evaluated at a mean of 4.3 weeks (recheck-1), and again at a mean of 5.4 months (recheck-2). Clinical improvement was observed, and significant decreases in thyroxine concentrations were measured at recheck-1 (mean: 39.57nmol/L, SEM: 14.4, SD: 41.2) and recheck-2 (mean: 36.71nmol/L, SEM: 13.9, SD: 45.56) compared to pretreatment concentrations (mean: 97.5nmol/L, SEM: 11.42, SD: 39.5). No adverse effects were reported.

Topics: Administration, Cutaneous; Animals; Antithyroid Agents; Cat Diseases; Cats; Ear, External; Female; Hyperthyroidism; Male; Methimazole; Records; Retrospective Studies; Thyroxine; Treatment Outcome

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Diagnosis, Differential; Fatal Outcome; Hydrothorax; Hyperthyroidism; Lung Diseases; Male; Methimazole; Pleural Diseases; Radiography, Thoracic; Torsion Abnormality

The intravenous and oral disposition of the antithyroid drug methimazole was determined in 10 clinically normal cats and nine cats with naturally occurring hyperthyroidism. After intravenous administration of 5 mg methimazole, the mean residence time was significantly (P less than 0.05) shorter in the cats with hyperthyroidism than in the normal cats, but there was no significant difference between the mean values for total body clearance (CL), steady state volume of distribution (Vdss), terminal elimination rate constant (ke), or serum terminal half-life (t1/2) in the two groups of cats. After oral administration, the mean bioavailability of methimazole was high in both the normal cats (77.6 per cent) and cats with hyperthyroidism (79.5 per cent). The values for mean residence time, ke and serum terminal t1/2 after oral dosing were significantly shorter in the cats with hyperthyroidism than in the normal cats. However, after oral administration of methimazole there were no significant differences between the mean values for CL, Vdss, bioavailability and maximum serum concentrations or the time for maximal concentrations to be reached in the two groups of cats. Overall, most pharmacokinetic parameters for methimazole were not altered by the hyperthyroid state. However, the cats with hyperthyroidism did show a trend toward faster elimination of the drug compared with the normal cats, similar to what has been previously described for the antithyroid drug propylthiouracil in cats. These results also indicate that methimazole is well absorbed when administered orally and has a higher bioavailability than that of propylthiouracil in cats with hyperthyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Absorption; Administration, Oral; Animals; Biological Availability; Cat Diseases; Cats; Female; Hyperthyroidism; Injections, Intravenous; Male; Methimazole; Tissue Distribution