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Mycobutin

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Mycobutin

Mycobutin

SIDE EFFECTS

MYCOBUTIN (rifabutin) Capsules were generally well tolerated in the controlled clinical trials. Discontinuation of therapy due to an adverse event was required in 16% of patients receiving MYCOBUTIN (rifabutin) compared to 8% of patients receiving placebo in these trials. Primary reasons for discontinuation of MYCOBUTIN (rifabutin) were rash (4% of treated patients), gastrointestinal intolerance (3%), and neutropenia (2%).

The following table enumerates adverse experiences that occurred at a frequency of 1% or greater, among the patients treated with MYCOBUTIN (rifabutin) in studies 023 and 027.

CLINICAL ADVERSE EXPERIENCES REPORTED IN ≤ 1% OF PATIENTS TREATED WITH MYCOBUTIN (rifabutin)

ADVERSE EVENT MYCOBUTIN
(n = 566) %
PLACEBO
(n = 580) %
BODY AS A WHOLE
  Abdominal Pain 4 3
  Asthenia 1 1
  Chest Pain 1 1
  Fever 2 1
  Headache 3 5
  Pain 1 2
DIGESTIVE SYSTEM
  Anorexia 2 2
  Diarrhea 3 3
  Dyspepsia 3 1
  Eructation 3 1
  Flatulence 2 1
  Nausea 6 5
  Nausea and Vomiting 3 2
  Vomiting 1 1
MUSCULOSKELETAL SYSTEM
  Myalgia 2 1
NERVOUS SYSTEM
  Insomnia 1 1
SKIN AND APPENDAGES
  Rash 11 8
SPECIAL SENSES
  Taste Perversion 3 1
UROGENITAL SYSTEM
  Discolored Urine 30 6

Clinical Adverse Events Reported In < 1% of Patients Who Received Mycobutin (rifabutin)

Considering data from the 023 and 027 pivotal trials, and from other clinical studies, MYCOBUTIN (rifabutin) 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, and skin discoloration.

The following adverse events have occurred in more than one patient receiving MYCOBUTIN (rifabutin) , but an etiologic role has not been established: seizure, paresthesia, aphasia, confusion, and non-specific T wave changes on electrocardiogram.

When MYCOBUTIN (rifabutin) was administered at doses from 1050 mg/day to 2400 mg/day, generalized arthralgia and uveitis were reported. These adverse experiences abated when MYCOBUTIN (rifabutin) was discontinued.

The following table enumerates the changes in laboratory values that were considered as laboratory abnormalities in studies 023 and 027.

PERCENTAGE OF PATIENTS WITH LABORATORY ABNORMALITIES

LABORATORY ABNORMALITIES MYCOBUTIN
(n = 566) %
PLACEBO
(n = 580) %
Chemistry:
  Increased Alkaline Phosphatase1 < 1 3
  Increased SGOT2 7 12
  Increased SGPT2 9 11
Hematology:
  Anemia3 6 7
  Eosinophilia 1 1
  Leukopenia4 17 16
  Neutropenia5 25 20
  Thrombocytopenia6 5 4
INCLUDES GRADE 3 OR 4 TOXICITIES AS SPECIFIED:
1 all values > 450 U/L
2 all values > 150 U/L
3 all hemoglobin values < 8.0 g/dL
4 all WBC values < 1,500/mm3
5 all ANC values < 750/mm3
6 all platelet count values < 50,000/mm3

The incidence of neutropenia in patients treated with MYCOBUTIN (rifabutin) was significantly greater than in patients treated with placebo (p = 0.03). Although thrombocytopenia was not significantly more common among patients treated with MYCOBUTIN (rifabutin) in these trials, MYCOBUTIN (rifabutin) has been clearly linked to thrombocytopenia in rare cases. One patient in study 023 developed thrombotic thrombocytopenic purpura, which was attributed to MYCOBUTIN (rifabutin) .

Uveitis is rare when MYCOBUTIN (rifabutin) is used as a single agent at 300 mg/day for prophylaxis of MAC in HIV-infected persons, even with the concomitant use of fluconazole and/or macrolide antibiotics. However, if higher doses of MYCOBUTIN (rifabutin) 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 (rifabutin) and ophthalmologic evaluation are recommended. In most mild cases, MYCOBUTIN (rifabutin) may be restarted; however, if signs or symptoms recur, use of MYCOBUTIN (rifabutin) should be discontinued (Morbidity and Mortality Weekly Report, September 9, 1994).

Read the Mycobutin (rifabutin) Side Effects Center for a complete guide to possible side effects

DRUG INTERACTIONS

Effects on Other Drugs: Rifabutin induces CYP3A enzymes and therefore may reduce the plasma concentrations of drugs metabolized by those enzymes. This effect may reduce the efficacy of standard doses of such drugs, which include itraconazole, clarithromycin, and saquinavir (see CLINICAL PHARMACOLOGY - Drug-Drug Interactions).

Effects on Rifabutin: Some drugs that inhibit CYP3A may significantly increase the plasma concentration of rifabutin. Because high plasma levels of rifabutin may increase the risk of adverse reactions, carefully monitor patients receiving coadministration of such drugs, which include fluconazole and clarithromycin (see CLINICAL PHARMACOLOGY - Drug-Drug Interactions). In some cases, the dosage of MYCOBUTIN (rifabutin) may need to be reduced when it is coadministered with such a drug (see below).

Antiretrovirals

Delavirdine: Coadministration of rifabutin and delavirdine is not recommended because rifabutin substantially decreases the plasma concentrations of delavirdine, and delavirdine increases the plasma concentrations of rifabutin (see CLINICAL PHARMACOLOGY - Drug-Drug Interactions).

Indinavir: Coadministration of indinavir and rifabutin increases the plasma concentration of rifabutin. In patients receiving coadministration of indinavir, reduce the dosage of MYCOBUTIN by half (see CLINICAL PHARMACOLOGY - Drug-Drug Interactions).

Nelfinavir: Coadministration of nelfinavir increases the plasma concentration of rifabutin. In patients receiving nelfinavir, reduce the dosage of MYCOBUTIN by half (see CLINICAL PHARMACOLOGY - Drug-Drug Interactions).

Ritonavir: Coadministration of ritonavir is not recommended because it substantially increases the plasma concentration of rifabutin (see CLINICAL PHARMACOLOGY - Drug-Drug Interactions). High plasma concentrations of rifabutin may increase the risk of adverse reactions, including uveitis.

Other Drugs

Oral contraceptives: Rifabutin may decrease the efficacy of oral contraceptives by inducing drug metabolism of ethinylestradiol and norethindrone. Women using oral contraceptives should be advised to change to or supplement with nonhormonal methods of birth control during treatment with MYCOBUTIN (rifabutin) .

Other drugs: The structurally similar drug, rifampin, is known to reduce the plasma concentrations of a number of other drugs (see prescribing information for rifampin). Although rifabutin is a weaker enzyme inducer than rifampin, it may be expected to have some effect on those drugs as well.

Read the Mycobutin Drug Interactions Center for a complete guide to possible interactions

Last reviewed on RxList: 6/16/2008
This monograph has been modified to include the generic and brand name in many instances.

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