naphthoquinones and Toxoplasmosis--Cerebral

To review the chemistry, pharmacology, pharmacokinetics, clinical efficacy, and safety of atovaquone.. An English-language literature search using MEDLINE (1984-1993), programs and abstracts of the 30th, 31st, and 32nd Interscience Conferences on Antimicrobial Agents and Chemotherapy, program and abstracts of the VIII International Conference on AIDS, and unpublished information from Burroughs Wellcome, the manufacturer of atovaquone.. All available pharmacokinetic and clinical trials were reviewed.. Study quality was assessed by a critical appraisal of study design and methods. Pharmacokinetic studies were evaluated for sampling, methods used to determine pharmacokinetic properties, and the presence of concentration-response and concentration-toxicity relationships. Clinical trials were assessed primarily for comparative efficacy and toxicity.. Atovaquone is a novel hydroxynaphthoquinone with potent activity against Pneumocystis carinii and Toxoplasma gondii. Its pharmacokinetic properties are characterized by relatively poor bioavailability, excretion almost exclusively through the feces, lack of hepatic metabolism and urinary excretion, low steady-state plasma concentrations, high protein binding, and a long elimination half-life (50-70 h). Results from comparative clinical trials in AIDS patients with mild-to-moderate P. carinii pneumonia (PCP) reveal similar overall treatment success rates for atovaquone, trimethoprim/sulfamethoxazole (TMP/SMX), and pentamidine. Treatment failure because of lack of therapeutic response was significantly greater in patients who received atovaquone compared with those treated with TMP/SMX (p = 0.002). More atovaquone-patients experienced treatment failure compared with their pentamidine-treated counterparts, although statistical significance was not achieved. Treatment failure secondary to drug toxicity was significantly higher in the TMP/SMX- and pentamidine-treated patients (p < or = 0.01). Atovaquone has not been studied for PCP prophylaxis. Limited data exist on the use of atovaquone for toxoplasmic encephalitis (TE); however, results from an open trial reveal that the drug may be useful in treating this disorder. To date, atovaquone has been well tolerated by most patients administered the drug. The most common adverse effects include maculopapular rash, gastrointestinal disturbances, and fever. Atovaquone is considerably more costly than other oral agents used to treat PCP.. Atovaquone appears to be better tolerated but less effective than TMP/SMX and pentamidine in the treatment of mild-to-moderate PCP. There is not enough information available on the use of atovaquone for PCP prophylaxis or the treatment of TE to definitively describe its efficacy. Comparative clinical trials are needed to assess its role in this clinical setting.

Topics: AIDS-Related Opportunistic Infections; Animals; Antifungal Agents; Antiprotozoal Agents; Atovaquone; Clinical Trials as Topic; Humans; Male; Naphthoquinones; Pneumonia, Pneumocystis; Toxoplasmosis, Cerebral

To examine the efficacy of atovaquone as salvage therapy in patients with AIDS-related toxoplasmic encephalitis, 93 patients with AIDS and toxoplasmic encephalitis who were intolerant of standard therapy (pyrimethamine plus sulfadiazine or clindamycin) or for whom such therapy was failing were treated with atovaquone tablets (750 mg four times daily) for 18 weeks. Plasma levels of atovaquone were measured with high-pressure liquid chromatography, and the clinical and radiological responses and survival were compared according to median plasma concentration groups. During the acute-therapy phase (the first 6 weeks), the conditions of 52% and 37% of the patients, respectively, were clinically or radiologically improved; the conditions of 26% and 15% remained clinically or radiologically improved by week 18. Median survival for all patients was 189 days (Kaplan-Meier estimate). A post-hoc analysis revealed a positive relationship between clinical and radiological responses and median atovaquone plasma concentrations. Survival time among patients with high or medium median steady-state plasma concentrations (319 and 289 days) was significantly better than that among those with low plasma concentrations (114 days; P = .003 and P = .006, respectively).

Topics: Adult; AIDS-Related Opportunistic Infections; Antiprotozoal Agents; Atovaquone; Brain; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Naphthoquinones; Salvage Therapy; Tomography, X-Ray Computed; Toxoplasmosis, Cerebral

To evaluate the efficacy and tolerance of atovaquone used as long-term maintenance therapy in patients with toxoplasmic encephalitis and intolerant of conventional anti-Toxoplasma therapies.. Uncontrolled open-label study of atovaquone given through an expanded access programme; statistical analysis was performed on an intent-to-treat basis.. Sixty-five patients intolerant of conventional toxoplasmic encephalitis therapies-pyrimethamine, sulphadiazine or clindamycin-received atovaquone as maintenance therapy after resolution of an acute episode of toxoplasmic encephalitis. Patients were clinically and neurologically evaluated monthly. Toxoplasmic encephalitis relapse was defined as the occurrence of neurological abnormalities, except in the case of a proven alternative diagnosis.. Sixty-five patients were treated with atovaquone 750 mg four times daily and followed up for a mean period of 1 year. Mean CD4 lymphocytes count was 29 x 10(6)/l. Prior to starting atovaquone, patients had experienced a total of 129 episodes of intolerance to conventional anti-Toxoplasma drugs. Atovaquone was used as a single anti-toxoplasmic agent in 75% of the cases. Seventeen patients (26%) experienced a toxoplasmic encephalitis relapse. Sixty-three patients (97%) were able to tolerate and continued taking atovaquone. Two patients had to discontinue therapy because of side-effects. In a multivariate analysis, only the duration of pyrimethamine-sulphadiazine therapy during the acute therapy phase of toxoplasmic encephalitis was significantly associated with a decreased risk of toxoplasmic encephalitis relapse during maintenance therapy [relative risk, 0.64 for each week of pyrimethamine-sulphadiazine; 95% confidence interval (CI), 0.42-0.96; P = 0.03]. The survival probability was 70% at 1 year after the episode of toxoplasmic encephalitis (95% CI, 57-83).. These results suggest that atovaquone is a well-tolerated alternative anti-Toxoplasma treatment for maintenance therapy in patients who are intolerant to conventional anti-Toxoplasma drugs.

Topics: Acquired Immunodeficiency Syndrome; Adult; Antiprotozoal Agents; Atovaquone; Clindamycin; Encephalitis; Female; Humans; Male; Naphthoquinones; Pyrimethamine; Recurrence; Risk Factors; Sulfadiazine; Survival Analysis; Time Factors; Toxoplasmosis, Cerebral

Atovaquone (formerly 566C80) is a hydroxynaphthoquinone with potent activity against Toxoplasma in vitro and in laboratory animals. Eight patients with AIDS and presumed or biopsy confirmed toxoplasmosis who were intolerant of or had not responded to standard therapies were treated with oral atovaquone 750 mg four times a day. Seven patients showed radiographic improvement; the other remained radiographically stable. Six patients died 6-60 weeks after enrollment with no clinical (six) or necropsy (three) evidence of recurrent toxoplasmosis; two patients relapsed at 10 and 32 weeks. Toxicity was mild: only one patient required temporary discontinuation of drug due to a rash. Atovaquone is a well-tolerated drug that appears to be an effective alternative for patients with toxoplasmosis who are intolerant of standard therapies.

Topics: Acquired Immunodeficiency Syndrome; Administration, Oral; Adult; Anti-Infective Agents; Atovaquone; Biopsy; Enzyme-Linked Immunosorbent Assay; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Naphthoquinones; Recurrence; Toxoplasmosis, Cerebral

Acute therapy with pyrimethamine plus sulfadiazine is the treatment of choice for reactivated toxoplasmic encephalitis (TE). Acute therapy is followed by lifelong maintenance therapy (secondary prophylaxis) with the same drugs at lower dosages. The use of pyrimethamine plus sulfadiazine is hampered by severe side effects including allergic reactions and hematotoxicity. Alternative treatment regimens with pyrimethamine plus clindamycin or other antiparasitic drugs are less efficacious. Atovaquone nanosuspensions show excellent therapeutic effects for "acute" intravenous (i.v.) treatment of reactivated TE in a murine model. In the present study, the therapeutic efficacy of atovaquone for oral "maintenance" therapy was investigated. Mice with a targeted mutation in the interferon regulatory factor 8 gene were latently infected with Toxoplasma gondii, developed reactivated TE, and received acute i.v. therapy with atovaquone nanosuspensions. Mice were then treated orally with atovaquone suspension or other antiparasitic drugs to prevent relapse of TE. Maintenance therapy with atovaquone at daily doses of 50 or 100 mg/kg (body weight) protected mice against reactivated TE and death. This maintenance treatment was superior to standard therapy with pyrimethamine plus sulfadiazine. The latter combination was superior to the combination of pyrimethamine plus clindamycin. Inflammatory changes in the brain parenchyma and meninges, as well as parasite numbers, in the brains of mice confirmed the therapeutic efficacy of atovaquone for maintenance therapy. Atovaquone was detectable in sera, brains, livers, and lungs of infected mice by high-performance liquid chromatography and/or mass spectrometry. In conclusion, atovaquone appears to be superior to the standard maintenance therapy regimens in a murine model of reactivated TE. The therapeutic efficacy of atovaquone for maintenance therapy against TE should be further investigated in clinical trials.

Topics: Animals; Antiprotozoal Agents; Atovaquone; Brain; Brain Chemistry; Chromatography, High Pressure Liquid; Female; Injections, Intravenous; Liver; Lung; Mass Spectrometry; Meninges; Mice; Mice, Inbred C57BL; Naphthoquinones; Pyrimethamine; Sulfadiazine; Survival Analysis; Toxoplasmosis, Cerebral

To evaluate the effects of drug therapy on the clinical course of acute acquired Toxoplasma retinochoroiditis and on the number of Toxoplasma cysts present in the brain and ocular tissues in the hamster animal model.. The Syrian golden hamster animal model of Toxoplasma retinochoroiditis was used. In acute disease, systemically administered atovaquone was compared with conventional therapies (pyrimethamine combined with sulfadiazine; clindamycin; and spiramycin). The clinical course of the ocular disease was determined with retinal examination and photography of the fundus. The number of Toxoplasma cysts remaining after treatment was evaluated in aliquots of brain homogenate and in retinal tissue. The effect of atovaquone on cerebral Toxoplasma cyst count was also studied in chronic disease.. None of the drugs administered altered the course of the acute disease, judged by clinical examination. Atovaquone alone significantly reduced the number of cerebral Toxoplasma cysts after acute disease. Atovaquone also significantly reduced the cerebral Toxoplasma cyst count in chronic disease.. Tissue cysts are believed to be responsible for reactivation of Toxoplasma retinochoroiditis. Atovaquone has the potential to reduce the risk of recurrent disease.

Topics: Acute Disease; Animals; Anti-Bacterial Agents; Antiprotozoal Agents; Atovaquone; Brain; Chorioretinitis; Chronic Disease; Cricetinae; Disease Models, Animal; Drug Therapy, Combination; Female; Mesocricetus; Naphthoquinones; Retina; Toxoplasma; Toxoplasmosis, Cerebral; Toxoplasmosis, Ocular

The effectiveness of combinations of rifabutin with atovaquone, clindamycin, pyrimethamine, or sulfadiazine in the treatment of toxoplasmic encephalitis in a murine model was investigated. Doses of each drug that were not effective in reducing inflammation in the brain of mice with toxoplasmic encephalitis when used alone were used in combination with a dose of rifabutin which was minimally effective. At the end of each period of therapy (15 or 30 days), brains of mice were examined histopathologically and the severity of the inflammatory lesions scored. Treatment with rifabutin in combination with pyrimethamine or sulfadiazine did not reduce brain inflammation significantly when compared to treatment with each drug alone. In contrast, treatment with rifabutin plus atovaquone for 15 or 30 days or with rifabutin plus clindamycin for 15 days resulted in statistically significant reduction in the inflammation. These results suggest that combining rifabutin with certain drugs that are active against Toxoplasma gondii may be useful for the treatment of toxoplasmic encephalitis in humans and may allow for a reduction in dosage of either or both drugs with a resulting reduction in untoward side effects.

Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Antiprotozoal Agents; Atovaquone; Brain; Clindamycin; Disease Models, Animal; Drug Therapy, Combination; Encephalitis; Female; Mice; Mice, Inbred CBA; Naphthoquinones; Pyrimethamine; Rifabutin; Sulfadiazine; Toxoplasmosis, Cerebral; Treatment Outcome

Nineteen cases of cerebral toxoplasmosis (CTOX) are reported from a group of Edinburgh AIDS patients. All patients were severely immunodeficient at the time of presentation with CD4 count < 50 cells/mm3. Thirteen patients had suffered a previous AIDS-defining illness. In Edinburgh, CTOX has developed in 48% of patients who are seropositive for toxoplasma and have a CD4 count < 50 cells/mm3. It is estimated that at least half of the toxoplasma seropositive patients will develop CTOX if they survive for 21 months after reaching a time in their illness when the CD4 count = 50 cells/mm3. The incidence of CTOX in toxoplasma-seronegative patients with a CD4 count < 50 cells/mm3 is 1.3%. All patients showed improvement on treatment and there was no correlation between clinical or radiological features and patient survival. Those patients unable to tolerate first choice anti-toxoplasma therapy had a significantly shorter survival than the remainder but there was no single therapeutic regimen which conferred a survival advantage. Eighteen patients had died at the time of study and the median survival following diagnosis of cerebral toxoplasmosis was 10 months (range 3-38 months). Postmortem examination of the brain was available in 8, 4 of whom had concomitant cerebral lymphoma. The survival from AIDS or CD4 count = 50 cells/mm3 did not differ significantly between those with treated CTOX and a control group who had no toxoplasma infection, suggesting that treatment is reasonably effective. CTOX is a disease associated with severe HIV-related immunodeficiency and, in those with a CD4 count < 50 cells/mm3, occurs more than 35 times as frequently in toxoplasma-seropositive than toxoplasma-seronegative patients. Treatment is effective but the outcome of treated disease cannot be predicted from presenting clinical or radiological features. Concomitant space-occupying cerebral pathology is evident in 50% of post-mortem examinations.

Topics: Acquired Immunodeficiency Syndrome; Adult; Anti-Bacterial Agents; Anti-Infective Agents; Antifungal Agents; Atovaquone; Autopsy; Azithromycin; Brain; CD4 Lymphocyte Count; Clindamycin; Drug Therapy, Combination; Female; Humans; Incidence; Lymphoma, AIDS-Related; Male; Middle Aged; Naphthoquinones; Pyrimethamine; Retrospective Studies; Sulfadiazine; Toxoplasmosis, Cerebral; United Kingdom

Topics: Adult; AIDS-Related Opportunistic Infections; Antiprotozoal Agents; Atovaquone; Female; Humans; Naphthoquinones; Toxoplasmosis, Cerebral; Treatment Failure

Toxoplasma gondii is a ubiquitous parasite, which causes several serious diseases. Until the AIDS pandemic, toxoplasmic encephalitis was largely confined to the pharmacologically immune-suppressed and to cases of congenital transmission. T gondii is now one of the more commonly encountered opportunistic pathogens of advanced AIDS.

Topics: AIDS-Related Opportunistic Infections; Atovaquone; Clindamycin; Coccidiostats; Humans; Naphthoquinones; Pyrimethamine; Sulfadiazine; Toxoplasmosis, Cerebral

We describe a child and an adult infected with the human immunodeficiency virus (HIV) who developed cerebral lesions consistent with toxoplasmosis. A biopsy in the child and IgG ELISA in both patients confirmed the diagnosis of Toxoplasma gondii. The patients were initially treated with pyrimethamine, however, computerized tomography studies (CT scan) revealed progression of a left frontal and temporoparietal lesion. Therapy in the child was changed to pyrimethamine, clindamycin, and azithromycin. Repeat CT scan showed further disease progression and therapy was changed to high-dose pyrimethamine (3 mg/kg/d) and azithromycin. A subsequent CT scan disclosed further radiologic progression with increasing edema. The adult patient developed a maculopapular rash during attempted treatment with pyrimethamine.. Introduction of 2 (trans-4[4 chlorophenol] cyclohexy[3-hydroxy-1, 4 naphthoquinone] (HNPQ) an experimental antiparasitic compound previously used only in adult HIV clinical trials, was instituted in the child and rapid oral desensitization to pyrimethamine was initiated in the adult patient.. HNPQ resulted in resolution of the cerebral lesion in the child and rapid oral desensitization to pyrimethamine produced an excellent clinical response in the adult. To our knowledge, these are the first cases of childhood and adult cerebral toxoplasmosis treated successfully with HNPQ and rapid oral desensitization to pyrimethamine.. HNPQ and pyrimethamine desensitization should be considered as alternate modes of therapy in patients who become intolerant or fail to respond to traditional therapy for toxoplasmosis.

Topics: Adult; AIDS-Related Opportunistic Infections; Antiprotozoal Agents; Atovaquone; Child; Desensitization, Immunologic; Female; HIV Infections; Humans; Naphthoquinones; Pyrimethamine; Toxoplasmosis, Cerebral

Topics: Administration, Oral; Adult; Antifungal Agents; Antiprotozoal Agents; Atovaquone; Clinical Protocols; Drug Monitoring; Humans; Naphthoquinones; Pneumonia, Pneumocystis; Toxoplasmosis, Cerebral

Cerebral toxoplasmosis is the most common opportunistic infection of the central nervous system in AIDS patients. Its rate varies between 3-40% according to the prevalence of toxoplasmosis in the different geographic areas. Conventional treatments used for this pathology are: sulphadiacin or clindamycin plus pyrimethamine, but all can occasionally produce severe side effects. Therefore, the search for new alternative therapies is recommended.. Two cases of encephalic toxoplasmosis in AIDS patients who developed severe toxicity to conventional treatment with pyrimethamine and sulphadiacin and later to clindamycin are described.. The first patient had a complete clinical and neuroradiological curation using clarithromycin 2 g/day and pyrimethamine 50 mg/day for 6 weeks. At 22 months follow up with a maintenance dose of 1 g/day of clarithromycin, the patient still remains asymptomatic. The second patient was successfully treated with atovaquone (750 mg/6 h) for 8 weeks and at 12 months of follow up with a maintenance dose of 750 mg/8 h remains asymptomatic.. The authors believe that clarithromycin and atovaquone may constitute valid alternatives for the treatment of cerebral toxoplasmosis. Nonetheless, their use may, at present, be recommended only as an alternative for the cases of therapeutic failure or severe intolerance when the usual schedules are used.

Topics: Adult; AIDS-Related Opportunistic Infections; Animals; Atovaquone; Clarithromycin; Clindamycin; Drug Therapy, Combination; Folic Acid; Humans; Male; Naphthoquinones; Pyrimethamine; Sulfadiazine; Toxoplasma; Toxoplasmosis, Cerebral

The morphological effects of drug treatment with atovaquone in the brains of mice chronically infected with Toxoplasma gondii was examined by light and electron microscopy. As early as 1 and 2 weeks of treatment there appeared to be fewer tissue cysts compared to untreated controls and this reduction was more significant after 4 weeks treatment. There also appeared to be a decrease in the number of inflammatory nodules and the severity of the meningitis. Ultrastructurally, the cysts of both treated and control animals were located within host cells. There was a marked increase in both the number of cysts with lysed bradyzoites and the number of degenerate bradyzoites after 4 weeks treatment. It is probable that the drug is more active against the metabolically active immature bradyzoites than the mature organisms. Drug treatment does not appear to result in rupture of tissue cysts or release of Toxoplasma antigens since there is a reduction rather than an increase in the inflammatory response. This drug may be useful in treating chronic toxoplasmosis since it appears to be active against the bradyzoites reducing the parasite burden (cyst number) without initiating a destructive inflammatory response.

Topics: Animals; Antiprotozoal Agents; Atovaquone; Brain; Chronic Disease; Female; Mice; Mice, Inbred CBA; Microscopy, Electron; Naphthoquinones; Toxoplasmosis, Animal; Toxoplasmosis, Cerebral

Rifabutin, a semisynthetic derivative of rifamycin S, was examined alone and in combination with other drugs for activity in treatment of systemic toxoplasmosis and toxoplasmic encephalitis in murine models. One hundred percent of the mice infected with a lethal inoculum of tachyzoites or cysts of Toxoplasma gondii were protected against death by treatment with doses of 400 or 300 mg of rifabutin per kg administered alone for 10 days. Doses of 200 mg/kg protected at least 80% of the mice, and doses of 100 mg/kg protected 10 to 40% of the infected mice against death. Doses of 50 mg/kg were not protective but caused a delay in time to death. Combination of nonprotective (50-mg/kg) or slightly protective (100-mg/kg) doses of rifabutin with doses of sulfadiazine, pyrimethamine, clindamycin, or atovaquone that did not confer any protection against death from toxoplasmosis when administered alone resulted in remarkable enhancement of the in vivo activities of all of these drugs. Seventy-five percent of the infected mice survived when treated with 100 mg of rifabutin per kg per day combined with the ineffective dose of 10 mg of pyrimethamine per kg. A dose of 50 mg of rifabutin per kg in combination with the ineffective dosages of clindamycin (25 mg/kg/day), atovoquone (5 mg/kg/day), and sulfadiazine (80 mg per liter of drinking water) protected at least 80, 60, and 60% of the mice against death, respectively. The inflammatory responses in the brains of mice treated for 30 days with 200 mg of rifabutin per kg per day were significantly reduced compared with those in the brains of untreated controls. These observations suggest that clinical trials with rifabutin for treatment and prevention of human toxoplasmosis may be justified, particularly when the drug is used in combination with other drugs with activity against T. gondii.

Topics: Animals; Antiprotozoal Agents; Atovaquone; Brain; Clindamycin; Drug Therapy, Combination; Female; Mice; Mice, Inbred CBA; Naphthoquinones; Pyrimethamine; Rifabutin; Sulfadiazine; Toxoplasmosis, Animal; Toxoplasmosis, Cerebral

Topics: Acquired Immunodeficiency Syndrome; AIDS-Related Opportunistic Infections; Antiprotozoal Agents; Atovaquone; Drug Resistance, Microbial; Humans; Naphthoquinones; Toxoplasmosis, Cerebral