RIFABUTIN
DOSAGE
Adult: 5mg/kg once a day (oral). Usual dose is 300mg, although doses of up to 450mg are sometimes used.
Children: 5mg/kg once a day (limited data).
PREPARATIONS
Oral: 150mg capsules.
DRUG LEVEL MONITORING
Indications for monitoring:
Timing of sample:
ADVERSE EFFECTS
COMMON:
Reddish discolouration of urine, sweat, sputum, tears.
Haematological: Neutropaenia.
Gastrointestinal: Anorexia, nausea, vomiting, heartburn.
Hepatic: Transient increases in LFTs.
Opthalmic: Uveitis.
Dermatological: Rash.
SERIOUS:
Haematological: Anaemia, neutropaenia, thrombocytopaenia.
ADVERSE EFFECTS: MONITORING
Routine tests as per generic MDR-TB treatment monitoring guidelines.
INTERACTONS
Anti-arrhythmics: Accelerated metabolism of disopyramide.
Anticoagulants: Accelerated metabolism of coumarins (e.g. warfarin).
Anti-diabetics: Accelerated metabolism of tolbutamide and sulfonylureas (reduced effect).
Antiepileptics: Reduced plasma concentration of carbamazepine and phenytoin.
Antifungals: increased serum concentration of rifabutin with fluconazole, posaconazole, and voriconazole, and possibly itraconazole. Reduced serum concentrations of itraconazole, posaconazole and voriconazole. If benefit outweighs the risk, monitor antifungal serum concentrations (increase dose of voriconazole); and monitor for rifabutin adverse effects such as leukopaenia and uveitis.
Antipsychotics: Possible reduced plasma concentration of aripiprazole.
Antivirals: Please seek advice from an HIV physician before considering starting rifampicin in patients on anti-retrovirals due to the frequency of drug interactions: Increased serum concentration of rifabutin when given with: amprenavir, Fosamprenavir/ritonavir, Lopinavir/ritonavir, Ritonavir, and Tipranavir/ritonavir. Reduce dose of rifabutin. Consider alternative protease inhibitor to ritonavir.
Atovaquone: Reduced plasma concentrations of both rifabutin and atovaquone.
Contraceptives: Accelerated metabolism of oestrogens and progestogens (reduced contraceptive effect).
Corticosteroids: Possible accelerated metabolism of corticosteroids (reduced effect).
Hormone Replacement Therapy (HRT): Rifampicin would be expected to reduce the efficacy of HRT
Macrolides: Increased risk of neutropaenia with azithromycin; increased plasma concentration of rifabutin when taken with clarithromycin and possibly erythromycin (reduce dose of rifabutin).
P-aminosalicylic acid: Reduced absorption of rifamycins. Give 8-12 hours apart.
Sirolimus: Reduced in plasma concentration of sirolimus.
Tacrolimus: Reduced in plasma concentration of tacrolimus.
This information is not inclusive of all drug interactions. Please discuss with a pharmacist.
CONTRA-INDICATIONS & CAUTIONS
Contraindications:
Hypersensitivity: To rifabutin or other rifamycins.
Pregnancy.
Breast-feeding.
Cautions:
Liver Disease: Use cautiously and monitor LFTs.
Renal Disease: Reduce dose in severe renal impairment.
LABORATORY INFORMATION
Please find up to date information at www.assayfinder.com regarding individual providers of drug level monitoring tests. Click on the provider to discover contact details. Turnaround time varies depending on the test and whether it is run locally or sent to an external lab. By contacting laboratories in advance, turnaround time can significantly be reduced.
Sample Type: Serum.
Volume Required: 2 ml.
Sample Container: Plain (non SST).
Container Type: Any.
Availability: Office Hours.
Turnaround Time: 7 Days.
Adult: 5mg/kg once a day (oral). Usual dose is 300mg, although doses of up to 450mg are sometimes used.
Children: 5mg/kg once a day (limited data).
PREPARATIONS
Oral: 150mg capsules.
DRUG LEVEL MONITORING
Indications for monitoring:
- Known or suspected malabsorption.
- Poor treatment response.
Timing of sample:
- 3 hours post dose.
- Repeat at 7 hours if suspect delayed.
- Drug levels need not be routinely measured.
ADVERSE EFFECTS
COMMON:
Reddish discolouration of urine, sweat, sputum, tears.
Haematological: Neutropaenia.
Gastrointestinal: Anorexia, nausea, vomiting, heartburn.
Hepatic: Transient increases in LFTs.
Opthalmic: Uveitis.
Dermatological: Rash.
SERIOUS:
Haematological: Anaemia, neutropaenia, thrombocytopaenia.
ADVERSE EFFECTS: MONITORING
Routine tests as per generic MDR-TB treatment monitoring guidelines.
INTERACTONS
Anti-arrhythmics: Accelerated metabolism of disopyramide.
Anticoagulants: Accelerated metabolism of coumarins (e.g. warfarin).
Anti-diabetics: Accelerated metabolism of tolbutamide and sulfonylureas (reduced effect).
Antiepileptics: Reduced plasma concentration of carbamazepine and phenytoin.
Antifungals: increased serum concentration of rifabutin with fluconazole, posaconazole, and voriconazole, and possibly itraconazole. Reduced serum concentrations of itraconazole, posaconazole and voriconazole. If benefit outweighs the risk, monitor antifungal serum concentrations (increase dose of voriconazole); and monitor for rifabutin adverse effects such as leukopaenia and uveitis.
Antipsychotics: Possible reduced plasma concentration of aripiprazole.
Antivirals: Please seek advice from an HIV physician before considering starting rifampicin in patients on anti-retrovirals due to the frequency of drug interactions: Increased serum concentration of rifabutin when given with: amprenavir, Fosamprenavir/ritonavir, Lopinavir/ritonavir, Ritonavir, and Tipranavir/ritonavir. Reduce dose of rifabutin. Consider alternative protease inhibitor to ritonavir.
Atovaquone: Reduced plasma concentrations of both rifabutin and atovaquone.
Contraceptives: Accelerated metabolism of oestrogens and progestogens (reduced contraceptive effect).
Corticosteroids: Possible accelerated metabolism of corticosteroids (reduced effect).
Hormone Replacement Therapy (HRT): Rifampicin would be expected to reduce the efficacy of HRT
Macrolides: Increased risk of neutropaenia with azithromycin; increased plasma concentration of rifabutin when taken with clarithromycin and possibly erythromycin (reduce dose of rifabutin).
P-aminosalicylic acid: Reduced absorption of rifamycins. Give 8-12 hours apart.
Sirolimus: Reduced in plasma concentration of sirolimus.
Tacrolimus: Reduced in plasma concentration of tacrolimus.
This information is not inclusive of all drug interactions. Please discuss with a pharmacist.
CONTRA-INDICATIONS & CAUTIONS
Contraindications:
Hypersensitivity: To rifabutin or other rifamycins.
Pregnancy.
Breast-feeding.
Cautions:
Liver Disease: Use cautiously and monitor LFTs.
Renal Disease: Reduce dose in severe renal impairment.
LABORATORY INFORMATION
Please find up to date information at www.assayfinder.com regarding individual providers of drug level monitoring tests. Click on the provider to discover contact details. Turnaround time varies depending on the test and whether it is run locally or sent to an external lab. By contacting laboratories in advance, turnaround time can significantly be reduced.
Sample Type: Serum.
Volume Required: 2 ml.
Sample Container: Plain (non SST).
Container Type: Any.
Availability: Office Hours.
Turnaround Time: 7 Days.