Considering data from the 023 and 027 pivotal trials, and from other clinical studies, MYCOBUTIN appears to be a likely cause of the following adverse events which occurred in less than 1% of treated patients: flu-like syndrome, hepatitis, hemolysis, arthralgia, myositis, chest pressure or pain with dyspnea, skin discoloration, thrombocytopenia, pancytopenia and jaundice.
The following adverse events have occurred in more than one patient receiving MYCOBUTIN, but an etiologic role has not been established: seizure, paresthesia, aphasia, confusion, and non-specific T wave changes on electrocardiogram.
When MYCOBUTIN was administered at doses from 1050 mg/day to 2400 mg/day, generalized arthralgia and uveitis were reported. These adverse experiences abated when MYCOBUTIN was discontinued.
Mild to severe, reversible uveitis has been reported less frequently when MYCOBUTIN is used at 300 mg as monotherapy in MAC prophylaxis versus MYCOBUTIN in combination with clarithromycin for MAC treatment (see also WARNINGS).
Uveitis has been infrequently reported when MYCOBUTIN is used at 300 mg/day as monotherapy in MAC prophylaxis of HIV-infected persons, even with the concomitant use of fluconazole and/or macrolide antibacterials. However, if higher doses of MYCOBUTIN are administered in combination with these agents, the incidence of uveitis is higher.
Patients who developed uveitis had mild to severe symptoms that resolved after treatment with corticosteroids and/or mydriatic eye drops; in some severe cases, however, resolution of symptoms occurred after several weeks.
When uveitis occurs, temporary discontinuance of MYCOBUTIN and ophthalmologic evaluation are recommended. In most mild cases, MYCOBUTIN may be restarted; however, if signs or symptoms recur, use of MYCOBUTIN should be discontinued (Morbidity and Mortality Weekly Report, September 9, 1994).
Corneal deposits have been reported during routine ophthalmologic surveillance of some HIV-positive pediatric patients receiving MYCOBUTIN as part of a multiple drug regimen for MAC prophylaxis. The deposits are tiny, almost transparent, asymptomatic peripheral and central corneal deposits, and do not impair vision.
The following table enumerates the changes in laboratory values that were considered as laboratory abnormalities in Studies 023 and 027.
|Laboratory abnormalities||MYCOBUTIN (n = 566) %||PLACEBO (n = 580) %|
|Includes grades 3 or 4 toxicities as specified:|
|Increased alkaline phosphatase *||<1||3|
|Increased SGOT †||7||12|
|Increased SGPT †||9||11|
The incidence of neutropenia in patients treated with MYCOBUTIN was significantly greater than in patients treated with placebo (p = 0.03). Although thrombocytopenia was not significantly more common among patients treated with MYCOBUTIN in these trials, MYCOBUTIN has been clearly linked to thrombocytopenia in rare cases. One patient in Study 023 developed thrombotic thrombocytopenic purpura, which was attributed to MYCOBUTIN.
Adverse reactions identified through post-marketing surveillance by system organ class (SOC) are listed below:
Blood and lymphatic system disorders: White blood cell disorders (including agranulocytosis, lymphopenia, granulocytopenia, neutropenia, white blood cell count decreased, neutrophil count decreased), platelet count decreased.
Immune system disorders: Hypersensitivity, bronchospasm, rash, and eosinophilia.
Gastrointestinal disorders: Clostridioides difficile colitis/Clostridioides difficile associated diarrhea.
Pyrexia, rash and other hypersensitivity reactions such as eosinophilia and bronchospasm might occur, as has been seen with other antibacterials.
A limited occurrence of skin discoloration has been reported.
MYCOBUTIN has been associated with the occurrence of DRESS as well as other SCARs such as SJS, TEN, and AGEP (see WARNINGS).
Hypersensitivity to rifamycins have been reported including flu-like symptoms, bronchospasm, hypotension, urticaria, angioedema, conjunctivitis, thrombocytopenia or neutropenia.
Liver abnormalities (increased bilirubin and liver weight) occurred in mice, rats and monkeys at doses (respectively) 0.5, 1, and 3 times the recommended human daily dose based on body surface area comparisons. Testicular atrophy occurred in baboons at doses 2 times the recommended human dose based on body surface area comparisons, and in rats at doses 6 times the recommended human daily dose based on body surface area comparisons.
No information is available on accidental overdosage in humans.
While there is no experience in the treatment of overdose with MYCOBUTIN Capsules, clinical experience with rifamycins suggests that gastric lavage to evacuate gastric contents (within a few hours of overdose), followed by instillation of an activated charcoal slurry into the stomach, may help absorb any remaining drug from the gastrointestinal tract.
Rifabutin is 85% protein bound and distributed extensively into tissues (Vss:8 to 9 L/kg). It is not primarily excreted via the urinary route (less than 10% as unchanged drug); therefore, neither hemodialysis nor forced diuresis is expected to enhance the systemic elimination of unchanged rifabutin from the body in a patient with an overdose of MYCOBUTIN.
It is recommended that MYCOBUTIN Capsules be administered at a dose of 300 mg once daily. For those patients with propensity to nausea, vomiting, or other gastrointestinal upset, administration of MYCOBUTIN at doses of 150 mg twice daily taken with food may be useful.
For patients with severe renal impairment (creatinine clearance less than 30 mL/min), consider reducing the dose of MYCOBUTIN by 50%, if toxicity is suspected. No dosage adjustment is required for patients with mild to moderate renal impairment. Reduction of the dose of MYCOBUTIN may also be needed for patients receiving concomitant treatment with certain other drugs (see PRECAUTIONS-Drug Interactions).
Mild hepatic impairment does not require a dose modification. The pharmacokinetics of rifabutin in patients with moderate and severe hepatic impairment is not known.
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