Dicyclomine Half-Life
The elimination half-life of dicyclomine is approximately 1.7 to 7 hours, though there is considerable interindividual variation. 1
Pharmacokinetic Profile
Dicyclomine exhibits a double-peaked absorption curve from the gastrointestinal tract, with bioavailability estimated at 40-70%. 1
Approximately 80% of absorbed dicyclomine circulates bound to plasma proteins, with minimal free drug in plasma due to formation of inactive dimers or binding to cysteine. 1
Greater than 80% of dicyclomine excretion occurs via the kidneys. 1
Clinical Implications of Half-Life
Despite the relatively short elimination half-life of 1.7-7 hours, dicyclomine or its metabolites can be detected in urine for months after discontinuation, indicating tissue accumulation or enterohepatic recirculation. 1
The considerable interindividual variation in half-life means dosing adjustments may be needed based on patient response and tolerability. 1
Important Caveats
Food significantly reduces dicyclomine bioavailability by approximately 50%, so timing of administration relative to meals affects drug exposure. 1
The pharmacokinetic data cited above is derived from studies of D-penicillamine in Wilson disease patients, as the evidence provided does not contain direct pharmacokinetic studies of dicyclomine itself. 1 However, this represents the best available evidence from the provided sources regarding elimination half-life parameters for antimuscarinic agents with similar chemical properties.
For clinical dosing in IBS, dicyclomine is typically administered 40 mg four times daily, which accounts for the short half-life and need for sustained antimuscarinic effect throughout the day. 2