Orforglipron's interactions: CYP3A4 and OATP1B inhibitors raise it, inducers lower it

Design

Six phase 1 drug-interaction studies

Population

Healthy adult volunteers

Primary outcome

Orforglipron and probe-drug pharmacokinetics

Effect

Exposure up with clarithromycin and ciclosporin, down with carbamazepine; no meaningful effect on midazolam, digoxin, atorvastatin

Orforglipron is an oral small-molecule GLP-1 receptor agonist that is a substrate of CYP3A4, OATP1B and P-glycoprotein. This Clinical Pharmacology and Therapeutics report, published in July 2026, brings together six phase 1 interaction studies in healthy volunteers.

Orforglipron exposure increased with clarithromycin, a strong CYP3A4 inhibitor, and with ciclosporin, which inhibits OATP1B strongly and CYP3A weakly. It decreased with carbamazepine, an inducer. Quinidine, a P-glycoprotein inhibitor, had no meaningful effect. As a perpetrator, orforglipron did not meaningfully change midazolam, digoxin or atorvastatin, and caused a weak increase in rosuvastatin consistent with BCRP inhibition. A rise in simvastatin acid was put down to simvastatin's own disposition rather than enzyme inhibition.

The abstract does not give the size of each change, so dose adjustments cannot be read from it. But the direction is clear enough to prescribe safely: think about CYP3A4 and OATP1B when an orforglipron patient starts or stops a macrolide, an antiepileptic inducer or ciclosporin.

• Expect higher orforglipron levels with clarithromycin and ciclosporin; watch for gastrointestinal side effects.
• Expect lower levels with carbamazepine and other strong inducers; glycaemic control may weaken.
• No meaningful effect on digoxin, midazolam or atorvastatin was seen.
• A weak rise in rosuvastatin exposure was seen; it is unlikely to need action in most patients.

Why it matters

Unlike injectable GLP-1 agonists, an oral small molecule brings a cytochrome interaction profile with it.

Don't overread it

Healthy-volunteer studies show direction, and the abstract gives no magnitudes to base dose changes on.

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