DRUG INTERACTIONS
Trospium is metabolized by ester hydrolysis and excreted by the kidneys through a combination of tubular secretion and glomerular filtration. Based on in vitro data, no clinically relevant metabolic drug-drug interactions are anticipated with SANCTURA XR®. However, some drugs which are actively secreted by the kidney may interact with SANCTURA XR® by competing for renal tubular secretion.
The concomitant use of SANCTURA XR® with other antimuscarinic agents that produce dry mouth, constipation, and other anticholinergic effects may increase the frequency and/or severity of such effects. SANCTURA XR® may potentially alter the absorption of some concomitantly administered drugs due to anticholinergic effects on gastrointestinal motility.
Digoxin
Concomitant use of trospium chloride 20mg twice daily and digoxin did not affect the pharmacokinetics of either drug [see Clinical Pharmacology ].
Antacid
While the systemic exposure of trospium on average was comparable with and without antacid containing aluminum hydroxide and magnesium carbonate, 5 out of 11 individuals in a drug interaction study demonstrated either an increase or decrease in trospium exposure, in presence of antacid. The clinical relevance of these findings is not known [see Clinical Pharmacology].
Metformin
Co-administration of 500 mg metformin immediate release tablets twice daily reduced the steady-state systemic exposure of trospium by approximately 29% for mean AUC(0-24) and by 34% for mean Cmax. The effect of a decrease in trospium exposure on the efficacy of SANCTURA XR® is unknown. The steady-state pharmacokinetics of metformin were comparable when administered with or without 60 mg SANCTURA XR® once daily under fasted condition. The effect of metformin at higher doses on trospium PK is unknown [see Clinical Pharmacology].
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