Marijuana cardiovascular effects

Marijuana has several effects on the cardiovascular system, and can increase resting heart rate and supine blood pressure and cause postural hypotension. It is associated with an increase in myocardial oxygen demand and a decrease in oxygen supply. Peripheral vasodilatation, with increased blood flow, orthostatic hypotension, and tachycardia, can occur with normal recreational doses of cannabis. High doses of THC taken intravenously have often been associated with ventricular extra beats, a shortened PR interval, and reduced T wave amplitude, to which tolerance readily develops and which are reversible on withdrawal. While the other cardiovascular effects tend to decrease in chronic smokers, the degree of tachycardia continues to be exaggerated with exercise, as shown by bicycle ergometry. 

Marijuana use is most popular among young adults (18-25 years old). However, with a generation of post-19608 smokers growing older, the use of marijuana in the age group that is prone to coronary artery disease has increased. The cardiovascular effects may present a risk to those with cardiovascular disorders, but in adults with normal cardiovascular function there is no evidence of... 

The second most common cardiovascular effect is an increase in heart rate and pulse rate (Kelly, Foltin, Fischman, 1993). Both of these effects last for about an hour, and each appears to be dose related. The peak heart rate occurs around 20 minutes after smoking. In addition to these effects, blood pressure tends to become slightly elevated. No evidence indicates that these effects create any permanent damage within the normal cardiovascular system (Institute of Medicine, 1982 Workshop on the Medical Utility of Marijuana, 1997). 

The vast majority of cardiovascular effects associated with cannabis smoking were described earlier in this section as short term (or acute). No evidence shows that smoking marijuana produces deleterious cardiovascular effects among healthy individuals. The acute effects produced (for example, increased heart rate) are, however, potentially dangerous among persons who have existing cardiovascular problems, such as abnormal heart functioning or atherosclerosis. 

F Although marijuana use does cause short-term increases in heart rate and pulse rate, no evidence shows that marijuana smoking produces deleterious cardiovascular effects in healthy individuals. The acute effects may be dangerous to individuals who have preexisting cardiovascular problems. 

The most abundant member of this group is the cannabinoid Al-THC-7-oic-acid. When tested in humans as well as in the rhesus monkey, this cannabinoid did not show the behavioral activity or the cardiovascular effects characteristic of the parent substance, THC. (Perez-Reyes, M. In Pharmacokinetics and Pharmacodynamics of Psychoactive Drugs, Barnett, G. and Chiang, N. (eds), Biomedical Press, 1985, pages 287-310 Mechoulam, R. and Edery, M. ln Marijuana, Mechoulam, R. (ed.), Academic Press, New York, 1973). Thus, little attention has been given to the possible pharmacodynamic properties of this metabolite or any of the other acid metabolites of THC. 

Cannabis and THC are known to increase heart rate, cardiac output and supine blood pressure, and can cause orthostatic hypotension (Jones 2002). Because of the resulting increase in cardiac work, cannabis and THC are probably best avoided by patients with clinically significant cardiovascular disorders. Cardiovascular effects tend to tolerate out over chronic dosing (Benowitz and Jones 1981). A survey of myocardial infarction survivors set out to investigate whether smoking marijuana... 

In view of the cardiovascular effects of marijuana, including tachycardia and a tendency to orthostatic hypotension, the use of cannabis by patients with cardiovascular disease is most certainly inadvisable. The older the individual, the greater the risk of unpleasant effects, including toxic psychoses. It would also seem better to avoid the use of marijuana in respiratory disease, in which it is likely to have some of the deleterious effects of tobacco smoking (SED VIII, p. 53). Finally, since cannabis passes the placental barrier, and in view of the many unanswered questions as to its basic effects, it would seem very unwise to take the material during pregnancy. The separate data on this topic have been reviewed very recently by Nis-himura and Tanimura (21 ). 

Jones, R. T. Cardiovascular system effects of marijuana. J Clin Pharmacol 2002 42(11 Suppl) 58S-63S. 

Data on the longer-term effects of marijuana unfortunately arc sparse and difficult to interpret. The research that has been conducted has focused on four central systems respiratory, cardiovascular, immune, and reproductive. 

Key Words Cannabis marijuana dronabinol human smoked adverse events cardiovascular neurological cognition performance subjective effects. 

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