MYCOBUTIN

What it is

Mycobutin (rifabutin) is a wide spectrum, semi-synthetic ansamycin antibiotic particularly active on acid-fast bacilli, including atypical and multidrug-resistant mycobacteria. Each Mycobutin capsule for oral administration contains 150 mg of rifabutin.

Approved indications

— Prophylaxis of M. avium-intracellulare complex (MAC) infections in patients with advanced HIV infection (CD4 counts lower than 200/μL). — Treatment of infections caused by MAC and other atypical mycobacteria, including in immunocompromised patients. — Treatment of chronic multidrug-resistant pulmonary tuberculosis in the presence of rifampicin resistant, rifabutin-sensitive M. tuberculosis strains. — Treatment of newly diagnosed pulmonary tuberculosis in the presence of rifampicin resistant, rifabutin-sensitive M. tuberculosis strains.

Dosing overview

Mycobutin can be administered as a single, daily, oral dose at any time independently of meals. Mycobutin should always be given in combination with other anti-mycobacterial drugs not belonging to the family of rifamycins. When Mycobutin is given in association with clarithromycin, the dosage of Mycobutin should be reduced to 300 mg once daily. When Mycobutin and indinavir are coadministered, the dosage of Mycobutin should be halved and the dosage of indinavir increased to 1,000 mg four times a day.

Key safety warnings

Mycobutin may impart a red-orange colour to the urine and possibly to skin and body secretions. Contact lenses, especially the soft variety, may be permanently stained. It is recommended that white blood cell and platelet counts and liver enzymes be monitored periodically during treatment, because Mycobutin may be associated with neutropenia and, more rarely, thrombocytopenia. Clostridium difficile associated diarrhoea (CDAD) has been reported with use of nearly all antibacterial agents, including rifabutin, and may range in severity from mild diarrhoea to fatal colitis. CDAD must be considered in all patients who present with diarrhoea following antibiotic use. There have been reports of severe cutaneous adverse reactions (SCARs), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalised exanthematous pustulosis (AGEP) with anti-tuberculosis drugs. If patients develop a skin rash they should be monitored closely and suspect drug(s) discontinued if lesions progress. Because of the possibility of occurrence of uveitis, patients should be carefully monitored when Mycobutin is given in combination with clarithromycin (or other macrolides) and/or fluconazole (and related compounds). If uveitis occurs, the patient should be referred to an ophthalmologist.

Contraindications

Mycobutin is contraindicated in patients with a history of hypersensitivity to rifabutin or other rifamycins (e.g., rifampicin). Due to insufficient clinical experience in children, Mycobutin should not be used in these patients. Concomitant use of ritonavir and rifabutin is contraindicated. Concomitant use with rilpivirine prolonged-release suspension for injection is contraindicated.

PBS listing

Mycobutin 150 mg capsules are listed on the PBS with 2 items, streamlined restriction, and an ex-manufacturer price of A$131.46.

Regulatory history

Mycobutin was first approved on 3 August 1994. The product (ARTG 55038, Mycobutin Rifabutin 150 mg capsule blister pack) was listed on the Australian Register of Therapeutic Goods on 2 May 2000.