trimpex and Avandia Interactions

Interactions between trimpex(trimethoprim) and Avandia (rosiglitazone)

trimethoprim and rosiglitazone (Moderate Drug-Drug)

MONITOR: Coadministration with trimethoprim may increase the plasma concentrations of rosiglitazone. The proposed mechanism is trimethoprim inhibition of CYP450 2C8, the isoenzyme primarily responsible for the metabolic clearance of rosiglitazone. In a study of 10 healthy volunteers, pretreatment with trimethoprim (160 mg orally twice a day for 4 days) increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of rosiglitazone (4 mg single oral dose) by 14% and 37%, respectively, compared to placebo. The half-life of rosiglitazone was prolonged from 3.8 to 4.8 hours. Nearly identical results were reported in eight healthy volunteers from another study.

MANAGEMENT: Close monitoring for the development of hypoglycemia and other adverse effects of rosiglitazone such as fluid retention, heart failure, and pulmonary and peripheral edema is recommended during coadministration with trimethoprim, particularly in patients receiving a higher dosage of rosiglitazone (e.g., 8 mg/day). Patients should be advised to regularly monitor their blood sugar and counseled on how to recognize and treat hypoglycemia, which may include symptoms such as headache, dizziness, drowsiness, nervousness, confusion, tremor, hunger, weakness, perspiration, and palpitations. The rosiglitazone dosage may require adjustment if an interaction is suspected.