trospium chloride + clarithromycin

This is a **combination of trospium chloride and clarithromycin**. Trospium chloride is an antimuscarinic (anticholinergic) agent used to treat overactive bladder, acting by competitively inhibiting muscarinic receptors in the bladder, thereby decreasing smooth muscle tone and involuntary contractions[3][6]. Clarithromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit. In this combination, clarithromycin is also notable as a strong inhibitor of the efflux transporter P-glycoprotein (P-gp), which is involved in the pharmacokinetics of trospium chloride. Studies have shown that coadministration of clarithromycin with trospium chloride leads to increased distribution volumes of trospium but does not significantly increase its oral bioavailability[1][5]. This interaction is related to clarithromycin-mediated P-gp inhibition, which impacts the absorption and distribution of trospium chloride[1][4][5]. The combination is not marketed as a fixed-dose drug product, but may arise in clinical settings as a pharmacokinetic interaction of interest.