Dicyclomine Safety in Pregnancy
Dicyclomine is classified as FDA Pregnancy Category B and can be used during pregnancy when clearly needed, as adequate studies have shown no evidence of harm to the fetus, though well-controlled human studies are limited. 1
FDA Classification and Safety Data
The FDA labels dicyclomine as Pregnancy Category B, indicating that reproduction studies in rats and rabbits at doses up to 33 times the maximum recommended human dose (based on 160 mg/day) revealed no evidence of fetal harm 1
Epidemiologic studies did not show an increased risk of structural malformations among babies born to women who took dicyclomine at doses up to 40 mg/day during the first trimester 1
However, adequate and well-controlled studies have not been conducted in pregnant women at the recommended therapeutic doses of 80-160 mg/day 1
Clinical Considerations for Use
Because animal reproduction studies are not always predictive of human response, dicyclomine should be used during pregnancy only if clearly needed 1
The decision to use dicyclomine should weigh the maternal benefit against the theoretical fetal risk, particularly when treating conditions like irritable bowel syndrome that significantly impact maternal quality of life 1
Historical Context: Bendectin Formulation
Dicyclomine was previously included in Bendectin (a three-part formulation with doxylamine and pyridoxine) used in the 1960s for pregnancy-related nausea 2, 3
A comprehensive meta-analysis of 16 cohort and 11 case-control studies found no increased risk of birth defects with Bendectin exposure, with a pooled relative risk of 0.95 (95% CI 0.88-1.04) for any malformation 2
However, a recent 2023 study raised concerns about a potential association between in utero Bendectin exposure and increased risk of adult-onset colorectal cancer in offspring (adjusted HR 3.38,95% CI 1.69-6.77), possibly driven by the dicyclomine component 3
Important Caveats
Dicyclomine is contraindicated in breastfeeding women, as it is excreted in human milk and poses potential serious adverse reactions in nursing infants 1
The drug is also contraindicated in infants less than 6 months of age due to reports of serious respiratory symptoms, seizures, and even death, though no causal relationship has been definitively established 1
The long-term effects suggested by the 2023 colorectal cancer study require experimental validation but warrant consideration when evaluating risk-benefit ratios 3
Practical Approach
Use dicyclomine only when the maternal condition clearly requires treatment and alternative therapies are inadequate 1
Employ the lowest effective dose for the shortest duration necessary 1
Avoid use during the first trimester if possible, though epidemiologic data at lower doses (up to 40 mg/day) have not shown increased malformation risk 1
Document the clinical indication and informed discussion with the patient regarding limited human data 1