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Drug interactions between Donnatal and omeprazole

Results for the following 2 drugs:
Donnatal (atropine/hyoscyamine/phenobarbital/scopolamine)

Interactions between your selected drugs


omeprazole ↔ phenobarbital

Applies to:omeprazole and Donnatal (atropine/hyoscyamine/phenobarbital/scopolamine)

Coadministration with inhibitors of CYP450 2C19 may theoretically increase the plasma concentrations of phenobarbital, which is a substrate of the isoenzyme. Some studies have reported an approximately 20% decrease in the total clearance of phenobarbital in individuals who are poor metabolizers of CYP450 2C19, although an interaction with specific CYP450 2C19 inhibitors has not been reported. Other studies have found no significant difference in the pharmacokinetics of phenobarbital amongst subjects with various CYP450 2C19 genotypes, which would suggest a minor role of CYP450 2C19 in the overall clearance of phenobarbital. No precautions appear to be necessary during coadministration of phenobarbital with CYP450 2C19 inhibitors. However, dosage adjustments may be necessary if an interaction is suspected.


  1. Klotz U "The role of pharmacogenetics in the metabolism of antiepileptic drugs: pharmacokinetic and therapeutic implications." Clin Pharmacokinet 46 (2007): 271-9

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Drug Interaction Classification

The classifications below are a guideline only. The relevance of a particular drug interaction to a specific patient is difficult to determine using this tool alone given the large number of variables that may apply.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No information available.

Do not stop taking any medications without consulting your healthcare provider.

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