The influence of dosage form on papaverine bioavailability

The bioavailability of sustained-release papaverine HCl dosage forms were compared to equivalent doses of the drug administered as an elixir and conventional compressed tablets to 12 healthy human subjects. Papaverine plasma levels were determined using a gas-chromatographic procedure. The drug was absorbed more rapidly and completely from the two nonsustained-release formulations. There was a large intersubject variability, and the plasma half-life of the drug was esstimated to be 1 hour. The area under the plasma level-time curve for the nine sustained-release products ranged from 18 to 64% relative to the area achieved by the papaverine elixir. It was concluded that the sustained-release dosage forms of papaverine included in each study group could be considered bioequivalent, but they exhibited inadequate bioavailability relative to either the elixir or the compressed tablet dosage form.