Certain drugs tend to produce hyperglycemia and may lead to loss of blood glucose control. These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel-blocking drugs, and isoniazid. When such drugs are administered to a patient receiving Randa, the patient should be closely observed for loss of blood glucose control. When such drugs are withdrawn from patients receiving Randa in combination with sulfonylureas or insulin, patients should be observed closely for any evidence of hypoglycemia.
Intestinal adsorbents (e. g., charcoal) and digestive enzyme preparations containing carbohydrate-splitting enzymes (e. g., amylase, pancreatin) may reduce the effect of Randa and should not be taken concomitantly.
Randa has been shown to change the bioavailabillty digoxin when they are co-administered, which may require digoxin dose adjustment.
Studies in healthy volunteers have shown that Randa has no effect on either the pharmacokinetics or pharmacodynamics of digoxin, nifedipine, propranolol, or ranitidine. Randa did not interfere with the absorption or disposition of the sulfonylurea glyburide in diabetic patients. Randa may affect digoxin bioavailabillty and may require dose adjustment of digoxin by 16% (90% confidence interval: 8-23%), decrease mean C max digoxin by 26% (90% confidence interval: 16-34%) and decrease mean trough concentrations of digoxin by 9% (90% confidence limit: 19% decrease to 2% increase).
The amount of metformin absorbed while taking Randa was bioequivalent to the amount absorbed when taking placebo, as indicated by the plasma AUC values. However, the peak plasma level of metformin was reduced by approximately 20% when taking Randa due to a slight delay in the absorption of metformin. There is little if any clinically significant interaction between Randa and metformin.