No abstract

1 Prizidilol hydrochloride (SK&F 92657) is a new compound which causes both arteriolar dilatation and ,/-adrenoceptor blockade. The effect of a single oral dose on the responses of heart rate and blood pressure to isoprenaline infusion has been studied in healthy volunteers.2 Isoprenaline heart rate dose-response curves showed parallel shifts to the right after oral prizidilol, indicating antagonism by this compound at ,3-adrenoceptors in the heart.3 Isoprenaline dose-response curves for decreases in diastolic blood pressure also showed shifts to the right after oral prizidilol, providing evidence of 8-adrenoceptor antagonism by this drug in peripheral resistance vessels. 4 The peak effect of a 40 mg dose of propranolol was greater than that of a 200 mg dose of prizidilol but both drugs caused persistent ,8-adrenoceptor blockade for at least 7 h after ingestion.

1 Ajmaline was found to have maximum fluorescence at neutral pH with 300 nm excitation and 365 nm emission wavelengths (corrected). 2 The fluorescence intensity had a linear relationship to concentration up to 50 gg ml-' and the recovery of ajmaline after extraction from plasma was 92.5 + 3%. 3 Extraction of drug-free plasma and of samples containing known concentrations of ajmaline showed that drug levels in the range found clinically could be measured accurately by fluorimetry. 4 Serial plasma ajmaline concentrations were measured in a subject after intravenous injection of ajmaline (50 mg). The rates of plasma clearance of the drug were found to be similar to those obtained in previous studies.