Are there any interactions between Oral Contraceptive Pills (OCPs), Buscopan (hyoscine butylbromide), and diclofenac 50mg?

Drug Interactions Between Oral Contraceptive Pills, Buscopan, and Diclofenac 50mg

No clinically significant interactions exist between oral contraceptive pills (OCPs), Buscopan (hyoscine butylbromide), and diclofenac 50mg, and these medications can be safely used together without reduced efficacy or increased risk of adverse effects.

Evaluation of Potential Interactions

Buscopan (Hyoscine Butylbromide) and OCPs

• Buscopan has extremely low systemic absorption (<1% bioavailability) after oral administration 1
• Due to its poor absorption and minimal systemic availability, Buscopan does not interact with the hepatic metabolism of oral contraceptives
• Buscopan primarily exerts local effects in the gastrointestinal tract and does not penetrate the blood-brain barrier 1
• No interactions between Buscopan and OCPs are documented in current contraceptive guidelines 2

Diclofenac and OCPs

• Diclofenac is not listed among medications that interact with hormonal contraceptives in the U.S. Selected Practice Recommendations for Contraceptive Use (2024) 2
• Unlike certain antibiotics (rifampin) or anticonvulsants (phenytoin, carbamazepine), diclofenac is not an enzyme inducer and does not reduce contraceptive effectiveness
• Non-steroidal anti-inflammatory drugs (NSAIDs) like diclofenac are not mentioned in the CDC's Medical Eligibility Criteria as having interactions with hormonal contraceptives 2

Medications Known to Interact with OCPs

For context, medications that DO interact with OCPs include:

1. Enzyme-inducing medications that can reduce OCP effectiveness:

   • Certain anticonvulsants (phenytoin, carbamazepine, barbiturates, primidone, topiramate, oxcarbazepine) 2
   • Rifampin and rifabutin 2
   • Some antiretroviral medications, particularly ritonavir-boosted protease inhibitors and certain non-nucleoside reverse transcriptase inhibitors (NNRTIs) like efavirenz 2

2. When these interacting medications are used, the CDC recommends:

   • Using an alternative contraceptive method, or
   • Using a higher dose OCP (containing at least 30μg ethinyl estradiol) 2
   • Adding a barrier method for additional protection 2

Clinical Recommendations

• Patients can safely take OCPs, Buscopan, and diclofenac 50mg concurrently without concerns about reduced contraceptive efficacy
• No dosage adjustments or additional contraceptive methods are required when using this combination
• The normal failure rate of OCPs (approximately 9% with typical use) still applies 2

Special Considerations

• If Buscopan causes significant vomiting (which is rare), and this occurs within 3 hours of taking an OCP, the contraceptive efficacy could be compromised due to inadequate absorption 2
• In this rare scenario, follow the missed pill guidelines as recommended by current contraceptive guidelines 2

This medication combination is safe and effective when used as prescribed, with no evidence of clinically significant pharmacokinetic or pharmacodynamic interactions that would warrant additional precautions.