INDEX Rifampicin

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. 

To prevent secondary cases of meningococcal disease prophylaxis with rifampicin 600 mg orally twice daily for two days is recommended for close contacts with the index case. A single dose of 500 mg ciprofloxacin orally is also effective in eliminating nasopharyngeal carriage of N. meningitidis. 

If liver damage occurs, isoniazid is probably an important factor and it should be stopped before rifampicin or pyrazinamide (8). Prediction of hepatotoxicity is possible (9). In a case-control study of 60 patients in India, conducted in order to identify features predicting hepatotoxicity, the body mass index was significantly lower (17.2 kg/m ) in patients who experienced hepatotoxicity than in controls (19.5 kg/m ) (10). 

Examples of chemoprophylaxis in the non-surgical arena include the prevention of endocarditis with amoxicillin in patients with valvular heart disease undergoing dental surgery, and the prevention of secondary cases of meningococcal meningitis with rifampicin among household contacts of an index case. 

A woman with Turner s syndrome, who had undergone a total thyroidectomy and who was being treated with levothyroxine 100 micrograms daily, had a marked fall in serum levothyroxine levels and free levothyroxine index with a dramatic rise in TSH levels when given rifampicin. However, no symptoms of clinical hypothyroidism developed, and the drop in serum levothyroxine occurred prior to starting rifampicin, which may reflect the clinicd picture of an acute infection. Another case describes a fall in TSH levels when rifampicin was discontinued. ... 

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