Names and pronunciation
(riff′a-byoo-ten) Mycobutin
PDF page 1152
Loading InternPractice…
Drug reference
(riff′a-byoo-ten) Mycobutin
PDF page 1152
Func. class.: Antimycobacterial agent
PDF page 1152
Chem. class.: Rifamycin S derivative
PDF page 1152
Do not confuse: rifabutin/rifAMPin/rifapentine
PDF page 1152
ACTION: Inhibits DNA-dependent RNA polymerase in susceptible strains of Escherichia coli and Bacillus subtilis; mechanism of action against Mycoba cterium avium unknown
PDF page 1153
USES: Prevention of M. avium complex (MAC) in patients with advanced HIV infection
PDF page 1153
Unlabeled uses: Helicobacter pylori that has not responded to other treatment, TB, MAC
PDF page 1153
CONTRAINDICATIONS: Hyper sensitivity, active TB, WBC <1000/mm3 or platelet count <50,000/mm3 Precautions: Pregnancy, breastfeeding, children, hepatic disease, blood dyscra sias
PDF page 1153
SIDE EFFECTS CNS: Headache, fatigue, anxiety, confu- sion, insomnia GI: Nausea, vomiting, anorexia, diar- rhea, heartburn, hepatitis, discolored saliva, CDAD GU: Discolored urine HEMA: Hemolytic anemia, eosinophilia, thrombocytopenia, leukopenia INTEG: Rash MISC: Flulike symptoms, shortness of breath, chest pressure MS: Asthenia, arthralgia, myalgia
PDF page 1153
INTERACTIONS Increase: levels of rifabutin—ritonavir Decrease: action of amprenavir, anticoagu- lants, β-blockers, barbiturates, busPIRone, clofibrate, corticosteroids, cycloSPORINE, dapsone, delavirdine, disopyramide, doxy- cycline, efavirenz, estrogens, fluconazole, indinavir, ketoconazole, losartan, nelfinavir, nevirapine, oral contraceptives, phenytoin, quiNIDine, saquinavir, sulfonylureas, the- ophylline, tricyclic antidepressants, zidovu- dine, zolpidem Drug/Food • High-fat diet decreases absorption Drug/Lab Test Interference: folate level, vit B12, BSP, gallbladder studies
PDF page 1153
DOSAGE AND ROUTES • Adult: PO 300 mg/day (may take as 150 mg bid); max 600 mg/day Renal dose • Adult: PO CCr <30 mL/min, reduce by 50%
PDF page 1153
Available forms: Caps 150 mg
PDF page 1153
Administer: • With food if GI upset occurs; better to take on empty stomach 1 hr before or 2 hr after meals; high-fat foods slow ab- sorption; may take in 2 divided doses, may open capsule, mix with applesauce if unable to swallow whole cap • Antiemetic if vomiting occurs • After C&S completed; monthly to de- tect resistance
PDF page 1153
Assess: • Acute TB: chest x-ray, sputum culture, blood culture, biopsy of lymph nodes, PPD; Do not use in MAC prophylaxis in those with active TB • CBC for neutropenia, thrombocytope- nia, eosinophilia • CDAD: diarrhea, abdominal pain/ R cramping, fever, bloody stools; report im- mediately; may occur several weeks after discontinuing treatment • Signs of anemia: Hct, HB, fatigue • Hepatotoxicity: ALT, AST, bilirubin; as- sess weekly for decreased appetite, jaun- dice, dark urine, fatigue • Renal status before, each mo: BUN, cre- atinine, output, specific gravity, urinalysis
PDF page 1153
Evaluate: • Therapeutic response: not used for active TB because of risk for develop- ment of resistance to rifAMPin; culture negative
PDF page 1153
CLINICAL CONSIDERATIONS
PDF page 1153
Patient and caregiver information: • That patients using oral contraceptives should consider using nonhormonal methods of birth control, may decrease effect; to notify prescriber if pregnancy planned, suspected • That compliance with dosage sched- ule, duration necessary • That scheduled appointments must be kept because relapse may occur • That urine, feces, saliva, sputum, sweat, tears may be colored red-orange; that soft contact lenses may be perma- nently stained • To report flulike symptoms: exces- sive fatigue, anorexia, vomiting, sore throat; unusual bleeding, yellowish discoloration of skin, eyes; myositis: muscle or bone pain; diarrhea, fever, abdominal cramping, bloody stools
PDF pages 1153, 1154
PHARMACOKINETICS 53% absorbed, peak 2-3 hr, duration >24 hr, half-life 45 hr, metabolized in liver (active/inactive metabolites), excreted in urine primarily as metabolites
PDF page 1153
• Adult: PO 300 mg/day (may take as 150 mg bid); max 600 mg/day Renal dose
PDF page 1153
• Adult: PO CCr <30 mL/min, reduce by 50%
PDF page 1153