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Bioavailability of dihydroergotamine in man
British Journal of Clinical Pharmacology
|June 1, 1982
Summary
Dihydroergotamine (DHE) pharmacokinetics show low oral bioavailability due to first-pass metabolism. DHE oral doses up to 30 mg do not saturate this extraction, leading to linear kinetics.
Area of Science:
- Pharmacology
- Clinical Pharmacy
Background:
- Dihydroergotamine (DHE) is a medication used for various conditions.
- Understanding its pharmacokinetic profile is crucial for effective therapeutic use.
Purpose of the Study:
- To investigate the pharmacokinetics of dihydroergotamine (DHE) in plasma.
- To determine the absorption, bioavailability, and elimination characteristics of DHE after intravenous and oral administration.
Main Methods:
- Six normotensive subjects received single acute doses of DHE: 10 micrograms/kg intravenously and 10, 20, and 30 mg orally.
- Plasma concentrations of DHE were analyzed to determine pharmacokinetic parameters.
Main Results:
- The mean apparent half-time of elimination for DHE was 2.37 ± 0.29 hours, with a plasma clearance of 1002 ± 169 ml/min.
- Mean apparent oral absorption was 26.6 ± 10%, with bioavailability averaging 0.47-0.59% across oral doses.
- Significant inter-patient variability (6-fold) in bioavailability was observed.
Conclusions:
- Pre-systemic 'first-pass' extraction significantly limits DHE's oral bioavailability.
- Oral DHE doses up to 30 mg do not saturate the extraction process, indicating linear kinetics within this range.