methimazole and Myalgia

Anti-thyroid drugs (ATDs), such as methimazole (MMI) and propylthiouracil (PTU), are the most common treatment options for hyperthyroidism. Although effective, well-known adverse effects include agranulocytosis, toxic hepatitis, vasculitis, and arthralgias. Myalgia and elevation of serum creatine kinase (CK) are relatively rare, with an unclear mechanism. Rapid decrease in the thyroid hormone level may be associated with ATD-related myopathy; however, direct effects of the drug on muscle tissue cannot be excluded. Here we report on two Chinese patients with myalgia and an elevated CK due to ATDs. Early recognition of this rare medication-induced adverse effect and close monitoring of the CK level are particularly important. Physicians and pharmacists should inform the patients about the earliest symptoms of adverse effects for patients to know when to discontinue the drug. If adverse events occur, different treatment strategies such as ATD dose reduction and switching to alternative ATDs can be applied depending on the case.

Topics: Antithyroid Agents; Creatine Kinase; Humans; Methimazole; Myalgia; Propylthiouracil

Myalgia and elevated creatine kinase (CK) have been reported during the treatment of hyperthyroid patients. The causes of these symptoms are usually considered to be treatments of antithyroid drugs (ATDs), thyroidectomy or radio-iodine (131-I). However, the underlying cause may be the rapid correction of thyrotoxicosis (or relative hypothyroidism), which was usually neglected in clinical practice.. This report describes a case of a 25-year-old female with typical symptoms and laboratory test results of Grave hyperthyroidism. The patient complained about fatigue and myalgia 7 weeks after receiving methimazole (MMI) treatment. Blood tests showed dramatically elevated serum CK level, although free triiodothyronine (FT3) and free thyroxine (FT4) level had returned to the normal reference range. MMI was; therefore, discontinued and the patient's muscular symptoms disappeared quickly with the normalization of CK level and the relapse of hyperthyroidism. Later she received 131-I treatment and suffered similar muscular symptoms when FT3 and FT4 decreased to the normal range. This time, her symptoms were quickly relieved by levothyroxine (L-T4) replacement treatment.. Myopathy induced by rapid correction of hyperthyroidism (or relative hypothyroidism).. MMI was discontinued after the patient's first episode of muscular symptoms. And for her second episode of muscular injury after 131-I treatment, we initiated L-T4 supplementation.. For the 2 episodes of muscular injury after ATDs or 131-I treatment, both of the interventions mentioned above brought a rapid relief of symptoms accompanied with normalization of CK level and restoration of thyroid hormone level.. Myopathy can be caused by a rapid reduction of thyroid hormone during the treatment of hyperthyroidism. This relative hypothyroidism syndrome should be considered if patients make complaints about fatigue and myalgia, even when thyroid hormone level is within the normal range during the antithyroid treatments. Serum CK level and thyroid function should be closely monitored post antithyroid treatments. Reduction of ATD dosage or replacement of thyroid hormone is suggested to relieve muscular symptoms.

Topics: Adult; Antithyroid Agents; Creatine Kinase; Female; Graves Disease; Humans; Methimazole; Myalgia; Recurrence; Thyroxine

Here, we reported two cases with hyperthyroidism who complained of myalgia and muscle cramps during treatment with methimazole tablets (or Thyrozol, the brand name). One case experienced muscle cramps after taking Thyrozol for 6 months, and by this time the patient's thyroid function had returned to normal. In the other case, pain caused by muscular cramps began after the patient took Thyrozol for two weeks and the patient's thyroid function had not returned to normal yet at the time. In both cases, pain caused by muscle cramps appeared while the patients were taking Thyrozol. The myalgia persisted in spite of a reduction in the Thyrozol dose, but was significantly relieved with the discontinuation of Thyrozol. Myalgia and muscle cramps did not recur after the patients were switched to methimazole ointment. There was a strong temporal association between oral administration of Thyrozol and pain caused by muscle cramps, which may indicate that myalgia and muscle cramps are adverse reactions of Thyrozol. Looking into the relevant literature on the topic, we explored in this report the possible mechanisms of the onset of muscle cramps associated with Thyrozol, and compared the adverse reactions of two different formulations of methimazole, intending to provide more clinical experience for the treatment of hyperthyroidism and the management of rare adverse reactions related to antithyroid drugs.

Topics: Humans; Hyperthyroidism; Methimazole; Muscle Cramp; Myalgia; Tablets

Here, we report a case of an increase in serum creatine kinase (CK) concentration in an 11-year-old girl being treated for Graves' disease with antithyroid drugs (ATDs). The patient complained of myalgia two weeks after methimazole treatment. Triiodothyronine (T3) and free thyroxine (FT4) levels were normal, but the serum CK level was significantly elevated. After switching to propylthiouracil, the serum CK level decreased to normal, and the myalgia was resolved. The development of myopathy during the treatment of hyperthyroidism may be considered as an adverse reaction of MMI. In this report, we present a rare pediatric case, along with a discussion on the possible causes of myopathy that occurred during the treatment of Graves' disease. A careful follow-up (serum CK levels and thyroid function) and treatment reassessment should always be considered after antithyroid treatment.

Topics: Antithyroid Agents; Child; Female; Graves Disease; Humans; Methimazole; Myalgia; Thyroxine; Triiodothyronine

A 62-year-old woman with a history of partially treated Graves disease and hypertension presented with approximately 3 weeks of worsening fatigue, lower extremity myalgias, and shortness of breath. Her medical history included a thyroid radiofrequency ablation several years earlier. Following the ablation, she was found to have some residual thyroid activity, negating the need for therapy. She was lost to follow-up after months of normal thyroid-stimulating hormone values. On this presentation, the patient was noted to be in atrial fibrillation with a rapid ventricular rate, and although she presented alert and oriented initially, she developed progressive inattentiveness and confusion while in the ED. The patient was transferred to the medical ICU for further management of her rapid heart rate and progressive delirium.

Topics: Anti-Arrhythmia Agents; Anti-Inflammatory Agents; Anticoagulants; Antithyroid Agents; Atrial Fibrillation; Delirium; Disseminated Intravascular Coagulation; Dyspnea; Fatal Outcome; Fatigue; Female; Femoral Artery; Graves Disease; Heparin; Humans; Hydrocortisone; Ischemia; Lower Extremity; Methimazole; Middle Aged; Myalgia; Pneumoperitoneum; Popliteal Artery; Potassium Iodide; Propranolol; Radiofrequency Ablation; Thrombosis; Thyroid Crisis; Tibial Arteries; Venous Thrombosis