Rifampicin oral contraceptives

Theophylline is a narrow therapeutic index drug with significant difference in bioavailability following oral administration. The half-life of the drug is increased by heart failure, cirrhosis and viral infections, in elderly patients, and by certain drugs, such as cimetidine, ciprofloxacin, oral contraceptives and fluvoxamine. The half-life is decreased in smokers, chronic alcoholism, and by certain drugs, such as phenytoin, rifampicin and carbamazepine. 

Rifabutin is a rifamycin used for prophylaxis against Mycobacterium avium complex infections in patients with low CD4 count. As with rifampicin it induces hepatic enzymes, although to a lesser extent than rifampicin, and the effectiveness of some drugs including oral contraceptives may be reduced. 

Rifampicin is a potent inducer of cytochrome P450 enzymes and thus can diminish the activity of a multitude of other agents such as warfarin, gluco-corticosteroids, cyclosporin, oral contraceptives and sulphonylurea-type oral antidiabetic agents. 

Sustained-release formulations can produce stable serum concentrations with once or twice daily dosage. Therapeutic effects occur at blood levels > 5 mg/1, and side effects increase considerably at levels > 15 mg/1. Smoking, alcohol, anticonvulsants, and rifampicin induce the drug-metabolizing enzyme system in liver and reduce the half-life of theophylline. On the other hand, heart and liver failure, sustained fever, old age and drugs such as cimeti-dine, ciprofloxacin, and oral contraceptives reduce theophylline clearance and thereby increase serum concentrations. 

Beta-blockers interact with a large number of other medications. The combination of beta-blockers with calcium antagonists should be avoided, given the risk for hypotension and cardiac arrhythmias. Cimetidine, hydralazine, and alcohol all increase blood levels of beta-blockers, whereas rifampicin decreases their concentrations. Beta-blockers may increase blood levels of phenothiazines and other neuroleptics, clonidine, phen-ytoin, anesthetics, lidocaine, epinephrine, monoamine oxidase inhibitors and other antidepressants, benzodiazepines, and thyroxine. Beta-blockers decrease the effects of insulin and oral hypoglycemic agents. Smoking, oral contraceptives, carbamazepine, and nonsteroidal anti-inflammatory analgesics decrease the effects of beta-blockers (Coffey, 1990). 

Drug Interactions Gemfibrozil Niacin Erythromycin Cholestyramine Digoxin Cimetidine/ranitidine/ omeprazole Rifampicin Warfarin Itraconazole Gemfibrozil Niacin Erythromycin Propranolol Digoxin Warfarin Antacids Colestipol Digoxin Erythromycin Oral contraceptives Fibrates Niacin Azole antifungals... 

Fluconazole Fluconazole may increase the plasma concentration of phenytoin, sulfonylurea (hypoglycemic), cyclosporin, zidovudine, cisapride, and terfenadine. Coadministration of fluconazole with rifampicin results in the reduced plasma concentration of fluconazole. Griseofulvin may reduce the plasma concentration of salicylates, coumarin, anticoagulants, and oral contraceptives. 

Which one of the following should not be taken with combined oral contraceptives (paracetamol/rifampicin/vitamin D/lithium/SSRIs)... 

Gupta KC, Ali MY (1980) Failure of oral contraceptive with rifampicin. Med... 

Several drugs, for example the oral contraceptive pill, viloxazine, thiabendazole, aminoglutethimide, antiepileptics (carbamazepine, phenytoin, barbiturates) and the antibiotic rifampicin decrease plasma concentrations of theophylline. 

Pruritus imassociated with rash e.g. oral contraceptives, phenothiazines, rifampicin (cholestatic reaction). 

Antibiotics, for example rifampicin (SEDA-8, 256), interfere with the hepatic metabohsm of the compounds in oral contraceptives. 

Reimers D, Jezek A. Rifampicin und andere Antituberkulohka bei gleichzeitiger oraler Kontrazeption. [The simultaneous use of rifampicin and other antitubercular agents with oral contraceptives.] Prax Pneumol 1971 25(5) 255-62. 

Compounds that may diminish the hypoglycaemic effect and thus cause an increase in the dosage requirement of sulphonylurea include rifampicin (Syvalahti et al., 1974). There is a theoretical risk of a diminished hypoglycaemic effect with corticosteroids and with oral contraceptives. It has been stated that the absorption of glibenclamide from the gastrointestinal tract may be reduced if it is taken together with guar gum. 

Clinically important, potentially hazardous interactions with amphotericin B, chlorotrianisene, colestyramine, diuretics, estrogens, furosemide, insulin, live vaccines, methotrexate, oral contraceptives, pancuronium, phenobarbital, rifampicin... 

Clinically important, potentially hazardous interactions with aluminum, aminophylline, aspirin, chlorambucil, cimetidine, clarithromycin, cyclophosphamide, cyclosporine, dicumarol, diuretics, docetaxel, estrogens, grapefruit juice, indomethacin, influenza vaccines, itraconazole, ketoconazole, lansoprazole, live vaccines, methotrexate, montelukast, omeprazole, oral contraceptives, pancuronium, phenobarbital, phenytoin, ranitidine, rifampicin, rifampin, timolol, tolbutamide, vitamin A... 

Clinically important, potentially hazardous interactions with aprepitant, astemizole, carbamazepine, colchicine, cyclosporine, dihydroergotamine, ergot alkaloids, ergotamine, erythromycin, fluoxetine, fluvoxamine, methylprednisolone, methysergide, oral contraceptives, paroxetine, pimozide, prednisolone, rifampicin, sertraline, solifenacin, terfenadine, warfarin... 

Rifampicin and phenobarbitai did not appear to alter thalidomide clearance in one study. Thalidomide increases the effect of other CNS depressants, and its CNS depressant activity is reduced by CNS stimulants. Thalidomide does not alter the pharmacokinetics of oral contraceptive steroids. 

In two studies rifabutin 300 mg daily for 10 or 14 days reduced the plasma levels of ethinylestradiol and norethisterone in women taking a combined oral contraceptive, but to a lesser extent than rifampicin. The AUC for ethinylestradiol decreased hy about 35% in both studies, and the AUC of norethisterone decreased by 17%. In one study, spotting occurred in 21.7% of women when they took rifabutin (compared with 3.7% in the control cycle and 36% with rifampicin). Ovulation did not occur with rifabutin or rifampicin in either study. - There appear to be no reports of contraceptive failure attributed to rifabutin. 

Reimers D, Nocke-Finck L, Breuer H. Rifampicin causes a lowering in efficacy of oral contraceptives by influencing oestrogen excretion. Reports on Rifampicin XXII International Tuberculosis Conference, Tokyo, September 1973, 87-9. 

Piguet B, Muglioni JF, Chaline G. Contraception orale et rifampicine. Now Presse Med (1975) 4,115-16. 

Skolnick JL, Stoler BS, Katz DB, Anderson WH. Rifampicin, oral contraceptives and pregnancy. (1976) 236, 1382. 

Gupta KC, Joshi JV, Anklesaria PS, Shah RS, Satoskar RS. Plasma rifampicin levels during oral contraception. J Assoc Physicians IruMa (1988) 36,365-6. 

Bolt HM, Kappus H, Bolt M. Rifampicin and oral contraception Lancet (1974) i, 1280-1. 

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