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Drug interactions between Donnatal and omeprazole

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

Interactions between your 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 and food interactions


scopolamine food

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

The coadministration with grapefruit juice may delay the absorption and increase the bioavailability of oral scopolamine. The proposed mechanism is delay of gastric emptying as well as inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In an open-label, crossover study consisting of 14 subjects, the consumption of grapefruit juice (compared to water) was associated with a 30% increase in mean systemic bioavailability and a 153% increase in time to reach peak serum concentration (Tmax) of scopolamine. However, the perceived pharmacodynamic effect of the drug, as measured by % change in subjective alertness compared to baseline, was similar after coadministration with water and grapefruit juice. Based on these findings, grapefruit juice is unlikely to affect the overall safety profile of of scopolamine but may delay its onset of action following oral administration. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability.


  1. Ebert U, Oertel R, Kirch W "Influence of grapefruit juice on scopolamine pharmacokinetics and pharmacodynamics in healthy male and female subjects." Int J Clin Pharm Therapeutics 38 (2000): 523-31

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Therapeutic duplication warnings

No therapeutic duplications were found for your selected drugs.

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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