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At least 523 records · Page 29Linked to original sources
PubMed1977

Prolonged delta-9-tetrahydrocannabinol ingestion. Effects of sympathomimetic amines and autonomic blockades.

In order to evaluate the possible effects of delta-9-tetrahydrocannabinol (THC) on autonomic nervous system function, cardiovascular responses to intravenous isoproterenol, phenylephrine, atropine, and propranolol were compared in hospitalized volunteers before and after 14 days of THC ingestion. There was no significant alteration in responses to isoproterenol or phenylephrine, although in one subject the pressor effect of phenylephrine was considerably augmented by THC. Heart rates after parasympathetic (atropine) blockade and after combined parasympathetic and sympathetic (propranolol) blockade were significantly greater during THC ingestion. These and other data presented are consistent with the picture of reduced sympathetic and enhanced parasympathetic activity described in animals on THC. During THC ingestion, atropine had a pronounced pressor effect, which might represent a clinically significant drug interaction.

Adult↗
PubMed1977

Influence of intrinsic sympathomimetic activity and cardioselectivity on beta adrenoceptor blockade.

Dose-response curves for propranolol and oxprenolol were studied in healthy volunteers, with a standardized excercise test and percentage reduction in excercise heart rate (EHR) as the index of drug effect. The dose-response curves obtained were compared with similar curves previously reported for sotalol, practolol, and atenolol with identical experimental methods. Two distinct types of response were identified: in the first, shown by propranolol and sotalol, increasing doses of the beta adrenoceptor-blocking drug continued to produce increasing effects to the limits of the dose levels examined; with the second (oxprenolol and practolol), increasing the dose initially resulted in substantial increase in effect but subsequently larger doses produced almost no increase in effect. Consideration of the additional properties of these beta adrenoceptor-blocking drugs revealed that both practolol and oxprenolol have intrinsic sympathomimetric activity (ISA), whereas propranolol and sotalol do not. In addition, practolol is cardioselective. Further investigation of the possible influence of ISA or cardioselectivity on beta adrenoceptor-blocking activity was undertaken by studying the effects of combinations of drugs on EHR. Sotalol produced greater effect when given 2 hr after sotalol, oxprenolol, practolol, or atenolol. When oxprenolol was given after sotalol or oxprenolol, or practolol was given after sotalol or practolol, there was no further increase in percentage reduction in EHR. When atenolol was given, the combinations of sotalol and atenolol together with two doses either of sotalol or atenolol all induced increases and similar final percentage reductions in EHR. Thus atenolol induces effects like those of sotalol, which are quite different from those of oxprenolol or practolol. The presence or absence of ISA would appear to be the important difference between these two groups of drugs: ISA would, therefore, appear to be demonstrated in man by flattening of the dose-response curves with exercise.

Adrenergic beta-Antagonists↗