Background: Rifampicin is a potent inducer of the hepatic microsomal enzyme system. However, the drug has been shown to cause clinically important interactions with many drugs. This study was designed to test the interaction of rifampicin with the oral hypoglycaemic agent glibenclamide.
Methods: Twenty-nine well-controlled diabetic patients on a combination therapy of diet and glibenclamide, and willing to participate in the trial, received a daily dose of 450 mg (body weight < 50 kg) or 600 mg (body-weight > 50kg) of rifampicin for 10 days.
Results: There was a significant (p < 0.001) worsening of fasting and post-prandial blood sugar after administration of rifampicin. Dose modification of glibenclamide was required in 15 of the 17 patients in whom the diabetes became uncontrolled. Blood sugar normalized by day 6 after stopping rifampicin in all patients.
Conclusion: Rifampicin and glibenclamide interact. Therefore, necessary dose modifications should be made in order to achieve euglycaemia if these two drugs are given together.