ABSTRACT
Results of studying the time variation of the miotic response intensity for periods of 6 to 8 hours after dosing in up to 16 normal human subjects who received various oral liquid and intravenous doses of chlorpromazine are reported. Relative to oral liquid doses of chlorpromazine syrup, intravenous doses of the drug slowly infused over a consistent time interval of 30 minutes are approximately 11 times as potent in eliciting miotic response activity. Miotic activity was found to be quite dose sensitive as seen from the response vs. time profiles and the dose-effect curves constructed as plots of areas under the response curves and peak response intensities. The dose-effect curves are approximately linear for both intravenous and oral dosing over the majority of the dose ranges studied. Pupilometry is demonstrated as providing a highly sensitive, reliable, rapid and convenient method for detecting differences in both rates and extents of systemic chlorpromazine bioavailability after parenteral or oral dosing with chlorpromazine. Pupilometry allows comparative bioavailability studies to be readily completed for low oral doses, e.g., 10 mg/70 kg, which are not possible to perform even under the most ideal conditions, using the best direct assay techniques presently available. It is precisely at such low oral doses that bioavailability between oral dosage forms are most pronounced and the use of pupilometry has its greatest utility.
Subject(s)
Chlorpromazine/metabolism , Miotics , Pupil/drug effects , Administration, Oral , Adult , Biological Availability , Chlorpromazine/administration & dosage , Chlorpromazine/pharmacology , Dose-Response Relationship, Drug , Enterohepatic Circulation , Humans , Injections, Intravenous , Male , Methods , Miotics/metabolism , Time FactorsABSTRACT
Owing to the insensitivity of even the presently best chemical or radiological assay procedures, it is not feasible to perform comparative bioavailability studies of chlorpromazine oral drug products using blood or urine sampling; this is particularly the case for oral doses below 100-150 mg/70 kg. In contrast, the use of temporal miotic response data, which correlates with blood levels of unchanged drug, permits dose-response vs time profiles to be recorded with oral dose levels as low as 5-10 mg/70 kg. The monitoring of pupilometric data in up to 16 human volunteers demonstrated a sensitivity to both extents and rates of chlorpromazine bioavailability and revealed differences to exist between liquid and solid oral dosage forms of chlorpromazine.
