Digitoxin elimination in healthy subjects taking ampicillin

Area of Science:

• Pharmacology
• Clinical Pharmacology
• Drug Interactions

Background:

• Digitoxin is a cardiac glycoside with a narrow therapeutic index.
• Ampicillin is a widely used broad-spectrum antibiotic.
• Potential drug interactions can alter the efficacy and safety of medications.

Purpose of the Study:

• To investigate the pharmacokinetic changes of digitoxin during concurrent administration with ampicillin.
• To determine if ampicillin affects the elimination half-life or other kinetic parameters of digitoxin.

Main Methods:

• A crossover study design involving six healthy volunteers.
• Administration of a single oral dose of digitoxin (1.0 mg).
• Subsequent administration of oral ampicillin trihydrate (500 mg four times daily for five days).
• Serial blood sampling for digitoxin concentration determination via radioimmunoassay.
• Serum ampicillin levels monitored to ensure compliance.

Main Results:

• The mean digitoxin elimination half-life showed a non-significant increase from 162.8 +/- 12.9 hours before ampicillin to 181.3 +/- 10.1 hours after ampicillin.
• No consistent evidence of a significant kinetic interaction between digitoxin and ampicillin was observed.
• Individual patient data did not reveal any clinically relevant alterations in digitoxin kinetics.

Conclusions:

• Ampicillin does not appear to significantly alter the pharmacokinetics of digitoxin in healthy individuals.
• The co-administration of digitoxin and ampicillin is unlikely to result in clinically significant drug interactions based on this study.
• Further research may be warranted in specific patient populations or with different dosing regimens.