Some cardiovascular effects of marihuana smoking in normal volunteers

Ventricular fibrillation triggered by marijuana use in a patient with ischemic cardiomyopathy: a case report

Background

A 60-year-old man presented to the emergency department with a left eye orbital rupture sustained during a fall due to syncope shortly after smoking more than his usual amount of marijuana.

Case presentation

The patient reported experiencing a shock from his implantable cardioverter-defibrillator (ICD) device prior to the loss of consciousness. There was no biochemical, electrocardiographic, or clinical evidence of ischemia. ICD interrogation revealed one episode of ventricular fibrillation which was appropriately sensed and treated with a single shock of 35 Joules.

Conclusion

Although the cardiovascular effects of marijuana are usually well tolerated in young healthy users, its use may trigger life-threatening arrhythmias in patients with structural heart disease. To the best of our knowledge, this is the first report on a case of ventricular fibrillation triggered by marijuana use in a patient with an ICD.

Frequency and irregularity of heart rate in drivers suspected of driving under the influence of cannabis

BACKGROUND

Delta 9-tetrahydrocannabinol (THC) is the major active component of cannabis. Cardiovascular effects of THC have previously been reported: tachycardia after intake, but also bradycardia at higher doses. The purpose of this study was, firstly, to investigate the frequency and irregularity of heart rate in a group of cannabis users in their natural surroundings. We also compared THC-positive drivers with a regular pulse with THC-positive drivers with an irregular pulse.

METHODS

The division of Forensic Toxicology and Drug Abuse (DFTDA) at the Norwegian Institute of Public Heath analyzes blood samples from all drivers suspected of driving under the influence of drugs. We studied pulse rate and regularity in 502 THC-positive drivers who tested negative for other substances. As a control group, we randomly selected 125 drug-negative cases from the database of the DFTDA; no alcohol, narcotics, or medicinal drugs of abuse were detected.

RESULTS

The Delta9-THC-positive drivers had a higher mean pulse rate than the control group [82.8 beats/min (SD 16.3) versus 75.6 beats/min (SD 9.2)] and more cases with tachycardia were detected in the Delta9-THC-positive group (19.4% versus 1.6%). There was only one driver with an irregular heart beat in the control group, while there were nine among the Delta9-THC-positive drivers. The drivers with an irregular pulse were over-represented amongst those with the lowest blood Delta9-THC concentrations.

CONCLUSION

This report represents a large study of subjects in a real-life situation and includes observations on pulse frequency, regularity, and blood Delta9-THC concentration. A substantial fraction of Delta9-THC-positive drivers had tachycardia, but there was no correlation between blood Delta9-THC concentration and pulse rate in the present study. We had no further diagnostic information on the cause of the pulse irregularities, but our results indicate that occasional users of cannabis tend to have irregular heart rates at low THC concentrations and at low pulse rates.

Atrial fibrillation and marijuana smoking

Marijuana is the most commonly used illicit drug while its abuse and dependence has an increasing prevalence among the young population. Marijuana smoking affects the circulatory system triggering various cardiovascular events. Of note, recent case reports indicate a possible association with atrial fibrillation (AF). In this article, we provide a brief systematic review of all reported cases implicating marijuana smoking in AF development and we concisely discuss the potential underlying mechanisms as well as the clinical implications of this emerging association.

Signal-averaged electrocardiogram in physically healthy, chronic 3,4-methylenedioxymethamphetamine (MDMA) users

OBJECTIVES

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) use has been associated with cardiac arrhythmias. Markers of ventricular late potentials (VLP), which may be a precursor to malignant ventricular arrhythmias, can be detected by signal-averaged electrocardiography (SA-ECG), but not by standard ECG.

METHODS

We evaluated SA-ECG parameters in 21 physically healthy, recently abstinent MDMA users who also used cannabis (11 males, mean [SD] age 23.3 [4.6] years, 2.8 [2.0] years of use), 18 physically healthy cannabis users (8 males, mean [SD] age 26.6 [7.1] years, 11.2 [5.4] years of use) and 54 non-drug-using controls (21 males, mean [SD] age 28.4 [7.8] years). We analyzed three SA-ECG parameters considered markers of VLPs: duration of filtered QRS complex (fQRS), duration of low amplitude potentials during terminal 40 ms of QRS complex (LAS40), and root mean square voltage during terminal 40 ms of QRS complex (RMS40).

RESULTS

MDMA users, cannabis users, and non-drug-using controls did not differ significantly from each other in fQRS, LAS40, or RMS40 values or in the proportion of subjects with abnormal SA-ECG parameters. There were significant gender differences among controls, but not among MDMA users.

CONCLUSION

These findings suggest that chronic MDMA use is neither quantitatively nor qualitatively associated with a high prevalence of abnormal SA-ECG parameters indicative of VLP markers.

Acute cannabis intoxication mimicking brugada-like ST segment abnormalities

A 19 years old male presented with a syncopeal episode after heavy marihuana use. A 12 lead ECG demonstrated Brugada-like ST segment elevation in leads V1 and V2. Urine and blood toxicological studies upon admission demonstrated markedly elevated levels of Tetrahydrocannabinol (THC). A 2D echocardiogram demonstrated normal left ventricular function without the presence of any structural or valvular abnormalities. The ST segments normalized once the acute intoxication resolved. A Procainamide induction test was performed without recurrence of the Brugada-like ST segment abnormalities. Our case exemplifies an otherwise healthy male with a negative work-up for a vasovagal mediated syncope and isolated ST segment changes due to THC. The arrhythmic properties of THC have been related to its effect on action potential shortening and vagal tone hyper-stimulation. The ST segment abnormalities are believed to be related to partial sodium channel agonist activity.

Cannabis-induced coronary artery thrombosis and acute anterior myocardial infarction in a young man

Information concerning acute myocardial infarction after cannabis usage is limited and the actual mechanism of cannabis-induced myocardial infarction is not well known. In the report, we described a young man with an acute myocardial infarction and cannabis-induced coronary thrombosis.

Marijuana use, diet, body mass index, and cardiovascular risk factors (from the CARDIA study)

Marijuana use has been associated with increased appetite, high caloric diet, acute increase in blood pressure, and decreases in high-density lipoprotein cholesterol and triglycerides. Marijuana is the most commonly used illicit drug in the United States, but its long-term effects on body mass index (BMI) and cardiovascular risk factors are unknown. Using 15 years of longitudinal data from 3,617 black and white young adults participating in the Coronary Artery Risk Development in Young Adults (CARDIA) study, we assessed whether marijuana use was associated with caloric intake, BMI, and cardiovascular risk factors. Of the 3,617 participants, 1,365 (38%) reported ever using marijuana. Marijuana use was associated with male gender, tobacco smoking, and other illicit drug use. More extensive marijuana use was associated with a higher caloric intake (2,746 kcal/day in never users to 3,365 kcal/day in those who used marijuana for > or = 1,800 days over 15 years) and alcohol intake (3.6 to 10.8 drinks/week), systolic blood pressure (112.7 to 116.5 mm Hg), and triglyceride levels (84 to 100 mg/dl or 0.95 to 1.13 mmol/L, all p values for trend < 0.001), but not with higher BMI and lipid and glucose levels. In multivariate analysis, the associations between marijuana use and systolic blood pressure and triglycerides disappeared, having been mainly confounded by greater alcohol use in marijuana users. In conclusion, although marijuana use was not independently associated with cardiovascular risk factors, it was associated with other unhealthy behaviors, such as high caloric diet, tobacco smoking, and other illicit drug use, which all have long-term detrimental effects on health.

Keep off the grass: marijuana use and acute cardiovascular events

Marijuana is one of the most widely used recreational substances in the world, considered by many consumers as a relatively safe drug with few significant side-effects. We report the case of a 21-year-old man who suffered an acute myocardial infarction following the use of marijuana, despite having no other identifiable risk factors for an acute cardiovascular event. We review the published medical literature regarding acute cardiovascular events following marijuana use and postulate a possible mechanism for this unusual pathological consequence of marijuana use.

Cannabis as a precipitant of cardiovascular emergencies

Cannabis smoking is on the increase both in the United Kingdom and in the United States. For over three decades it has been known that cannabis has pathophysiological effects on the cardiovascular system, and previously an association with an increased risk of myocardial infarction has been reported. However, it is not yet known whether cannabis contributes directly to coronary artery disease. We describe two distinct cases; in the first cannabis use precipitated a malignant arrhythmia in a patient with critical ischaemia from longstanding coronary artery disease. In the second, a young patient presented with an acute myocardial infarction that had started whilst smoking marijuana; subsequently diffuse coronary artery disease was found at angiography despite the patient's low risk factor status. Patients who are known cannabis smokers and who have cardiovascular disease should be warned that it is likely to aggravate coronary ischaemia, and may even trigger myocardial infarction.

Outcomes of coronary artery bypass grafting in patients with a history of illicit drug use

To date, no studies have been conducted on the effects of illicit drug use in patients with ischemic heart disease treated with coronary artery bypass grafting. Our retrospective study suggests that current illicit drug use is a significant predictor of cardiovascular complications in the first 6 months after coronary artery bypass grafting.

Cardiovascular manifestations of substance abuse: part 2: alcohol, amphetamines, heroin, cannabis, and caffeine

The abuse of alcohol is associated with chronic cardiomyopathy, hypertension, and arrhythmia. Abstinence or using alcohol in moderation can reverse these cardiovascular problems. Alcohol is also distinguished among the substances of abuse by having possible protective effects against coronary artery disease and stroke when used in moderate amounts. Amphetamines (eg, speed, ice, ecstasy) have many of the cardiovascular toxicities seen with cocaine, including acute and chronic cardiovascular diseases. Heroin and other opiates can cause arrhythmias and noncardiac pulmonary edema, and may reduce cardiac output. Cardiovascular problems are less common with cannabis (marijuana) than with opiates, but major cognitive disorders may be seen with its chronic use. It is still controversial whether caffeine can cause hypertension and coronary artery disease, and questions have been raised about its safety in patients with heart failure and arrhythmia.

Cardiovascular system effects of marijuana

Marijuana and delta9-tetrahydrocannabinol (THC) increase heart rate, slightly increase supine blood pressure, and on occasion produce marked orthostatic hypotension. Cardiovascular effects in animals are different, with bradycardia and hypotension the most typical response. Cardiac output increases, and peripheral vascular resistance and maximum exercise performance decrease. Tolerance to most of the initial cardiovascular effects appears rapidly. With repeated exposure, supine blood pressure decreases slightly, orthostatic hypotension disappears, blood volume increases, heart rate slows, and circulatory responses to exercise and Valsalva maneuver are diminished, consistent with centrally mediated, reduced sympathetic, and enhanced parasympathetic activity. Receptor-mediated and probably nonneuronal sites of action account for cannabinoid effects. The endocannabinoid system appears important in the modulation of many vascular functions. Marijuana's cardiovascular effects are not associated with serious health problems for most young, healthy users, although occasional myocardial infarction, stroke, and other adverse cardiovascular events are reported. Marijuana smoking by people with cardiovascular disease poses health risks because of the consequences of the resulting increased cardiac work, increased catecholamine levels, carboxyhemoglobin, and postural hypotension.

Triggering myocardial infarction by marijuana

BACKGROUND

Marijuana use in the age group prone to coronary artery disease is higher than it was in the past. Smoking marijuana is known to have hemodynamic consequences, including a dose-dependent increase in heart rate, supine hypertension, and postural hypotension; however, whether it can trigger the onset of myocardial infarction is unknown.

METHODS AND RESULTS

In the Determinants of Myocardial Infarction Onset Study, we interviewed 3882 patients (1258 women) with acute myocardial infarction an average of 4 days after infarction onset. We used the case-crossover study design to compare the reported use of marijuana in the hour preceding symptoms of myocardial infarction onset to its expected frequency using self-matched control data. Of the 3882 patients, 124 (3.2%) reported smoking marijuana in the prior year, 37 within 24 hours and 9 within 1 hour of myocardial infarction symptoms. Compared with nonusers, marijuana users were more likely to be men (94% versus 67%, P<0.001), current cigarette smokers (68% versus 32%, P<0.001), and obese (43% versus 32%, P=0.008). They were less likely to have a history of angina (12% versus 25%, P<0.001) or hypertension (30% versus 44%, P=0.002). The risk of myocardial infarction onset was elevated 4.8 times over baseline (95% confidence interval, 2.4 to 9.5) in the 60 minutes after marijuana use. The elevated risk rapidly decreased thereafter.

CONCLUSIONS

Smoking marijuana is a rare trigger of acute myocardial infarction. Understanding the mechanism through which marijuana causes infarction may provide insight into the triggering of myocardial infarction by this and other, more common stressors.

The effects of cannabinoids on the brain

Cannabinoids have a long history of consumption for recreational and medical reasons. The primary active constituent of the hemp plant Cannabis sativa is delta9-tetrahydrocannabinol (delta9-THC). In humans, psychoactive cannabinoids produce euphoria, enhancement of sensory perception, tachycardia, antinociception, difficulties in concentration and impairment of memory. The cognitive deficiencies seem to persist after withdrawal. The toxicity of marijuana has been underestimated for a long time, since recent findings revealed delta9-THC-induced cell death with shrinkage of neurons and DNA fragmentation in the hippocampus. The acute effects of cannabinoids as well as the development of tolerance are mediated by G protein-coupled cannabinoid receptors. The CB1 receptor and its splice variant CB1A, are found predominantly in the brain with highest densities in the hippocampus, cerebellum and striatum. The CB2 receptor is found predominantly in the spleen and in haemopoietic cells and has only 44% overall nucleotide sequence identity with the CB1 receptor. The existence of this receptor provided the molecular basis for the immunosuppressive actions of marijuana. The CB1 receptor mediates inhibition of adenylate cyclase, inhibition of N- and P/Q-type calcium channels, stimulation of potassium channels, and activation of mitogen-activated protein kinase. The CB2 receptor mediates inhibition of adenylate cyclase and activation of mitogen-activated protein kinase. The discovery of endogenous cannabinoid receptor ligands, anandamide (N-arachidonylethanolamine) and 2-arachidonylglycerol made the notion of a central cannabinoid neuromodulatory system plausible. Anandamide is released from neurons upon depolarization through a mechanism that requires calcium-dependent cleavage from a phospholipid precursor in neuronal membranes. The release of anandamide is followed by rapid uptake into the plasma and hydrolysis by fatty-acid amidohydrolase. The psychoactive cannabinoids increase the activity of dopaminergic neurons in the ventral tegmental area-mesolimbic pathway. Since these dopaminergic circuits are known to play a pivotal role in mediating the reinforcing (rewarding) effects of the most drugs of abuse, the enhanced dopaminergic drive elicited by the cannabinoids is thought to underlie the reinforcing and abuse properties of marijuana. Thus, cannabinoids share a final common neuronal action with other major drugs of abuse such as morphine, ethanol and nicotine in producing facilitation of the mesolimbic dopamine system.

Effects of chronic delta-9-THC treatment on cardiac beta-adrenoceptors in rats

This study was designed to determine if chronic treatment with delta-9-tetrahydrocannabinol (THC) alters cardiac beta-adrenoceptors in the rat. Following daily oral administration of 10 or 20 mg/kg THC or an equivalent volume of control solvent for 90 days, rats were sacrificed, and sarcolemmal membranes were prepared from ventricular myocardium. Beta-adrenoceptor density and binding affinity estimated with (-)[3H]dihydroalprenolol; a beta-adrenergic antagonist, were not significantly affected by treatment with THC when compared to vehicle controls. These results suggest that the tolerance to cardiovascular effects of THC which develops during chronic exposure in the rat is not associated with alterations in cardiac beta-adrenoceptors as monitored by radiolabeled antagonist binding.

delta 9-Tetrahydrocannabinol: EEG changes, bradycardia and hypothermia in the rhesus monkey

Administration of delta 9-tetrahydrocannabinol (THC; 0.75-4.0 mg/kg IP) to rhesus monkeys produced a biphasic pattern of high-voltage slow waves (HVSW) and fast waves (HVFW) EEG, along with behavioral depression and alertness, respectively. The HVSW phase appeared 20 to 30 min after drug injection and was uniquely characterized by spike-bursts in frontal and temporal lobes and hypothalamus, theta-waves in parietal and occipital lobes, and generalized HVSW in subcortical regions. During the HVSW phase, bradycardia and hypothermia occurred, and animals exhibited depression or sedation. After the HVSW phase lasting for 3-4 hr, HVFW predominated in overall EEGs with marked decrease in neocortical spike-bursts. Bradycardia and hypothermia occurred simultaneously 20 to 30 min after drug injection and reached maximal levels (30-40 percent decrease in heart rate, 1.5-2.0 degrees C decrease in body temperature) 2 to 3 hr after injection. The dose- and time-response relationships for bradycardia and hypothermia paralleled the HVSW phase with behavioral depression. Animals were alert and calm during recovery from bradycardia and hypothermia. THC levels and disposition in blood correlated with bradycardia, hypothermia and EEGs and behavioral changes following THC administration.

Cardiovascular effects of delta 9- and delta 9(11)-tetrahydrocannabinol and their interaction with epinephrine

The administration of delta-9-tetrahydrocannabinol (delta 9-THC, 0.078-5.0 mg/kg, i.v.) to rats anesthetized with pentobarbital caused as much as a 50% decrease in mean arterial blood pressure, heart rate and respiratory rate in a dose-dependent manner. Delta-9(11)-tetrahydrocannabinol (delta 9(11)-THC) was approximately 8-fold less potent than delta 9-THC in its hypotensive effect and had smaller effects on heart and respiratory rates that were not dose-related at doses below 5 mg/kg. Alternate injections of epinephrine (2 micrograms/kg) with vehicle and increasing cannabinoid doses (1.25-5.0 mg/kg) indicated a potentiation of both the duration of the pressor effect and the magnitude of the reflex bradycardic effect of epinephrine by both delta 9- and delta 9(11)-THC. Epinephrine also produced arrhythmias in rats receiving cannabinoids, but not in rats receiving alternate injections of vehicle. It is concluded that both cannabinoids have adverse effects on the cardiovascular system and adverse interactions with epinephrine in rats anesthetized with pentobarbital.

Behavioral factors and blood pressure in black college students

The relationship of behavioral factors and resting blood pressure was assessed in a random sample of 192 young middle class black adults. Framingham Type A behavior was positively associated with diastolic blood pressure (r = 0.17, p less than 0.05) among the women. Also, anger-in and trait anxiety were positively correlated with diastolic blood pressure for the women, r = 0.20, p less than 0.05 and r = +0.28 and p less than 0.01, respectively. After control for body mass index, trait anxiety and anger-in remained independent predictors of diastolic blood pressure among the women. For men, marijuana use was positively associated with blood pressure. Marijuana use was an independent predictor for systolic blood pressure after adjusting for body mass index among the males. The present study demonstrated a sex difference related to behavioral factors and blood pressure in young middle class blacks.

Marijuana smoking: effect on expired air carbon monoxide levels

A group of regular marijuana smokers was given expired air carbon monoxide (CO) tests before and after smoking low-dose, high-dose, and placebo marijuana cigarettes. Expired air CO doubled following smoking. There were no significant differences in CO levels in the different dose categories. Studies of the effects of marijuana on the body should attempt to separate effects of the drug from the effects that are secondary to the method of intake.

Health consequences of acute and chronic marihuana use

Chemical content, assay procedures, and pharmacokinetics of cannabis sativa are discussed briefly. Cannabinoid cellular effects relating to chromosomes and immunity including cellular metabolism and allergic reactions are presented. Gross and microscopic brain pathology due to cannabis use is reviewed involving EEG alterations, psychopathology including aggressive behaviour as well as properties of psychomotor impairment, tolerance and dependence. Cardiopulmonary effects of marihuana are recorded under pulmonary pharmacological effects including the macrophage defense system and effects of smoke constituents; under cardiovascular effects cardiac toxicity and possible mechanism of action are discussed. Alterations of reproductive hormonal production and maturation of reproductive cells by marihuana in males and females with attendant impairment of reproductive function or fertility including reproductive outcome are reported. Field studies with healthy chronic cannabis users in Jamaica, Greece and Costa Rica are related as to observed medical alterations. Potential clinical effects are summarized in point form.

Effects of acute marijuana smoking on pulse rate and mood states in women

The effects of marijuana cigarette (1.8% THC) smoking on pulse rate and mood were studied under double-blind placebo-controlled conditions in 28 adult female volunteers during the follicular, luteal, and ovulatory phases of the menstrual cycle. Statistically significant increases in pulse rate, subjective levels of intoxication, and the POMS confusion factor occurred after marijuana smoking. However, no statistically significant differences for any measure were observed following marijuana smoking as a function of menstrual cycle phase. Subjects with a past history of intermittent marijuana use (five or less times weekly) had significantly higher pulse rates, subjective levels of intoxication, and POMS confusion factor scores than did subjects with a past history of regular (six or more times weekly) marijuana use. Persistence of marijuana-induced changes in pulse rate, intoxication, and confusion were also of longer duration for subjects with a past history of intermittent marijuana smoking. The influence of past history of marijuana use on marijuana-induced alterations in pulse rate, intoxication, and mood for females appears to be similar to males. These similarities are not attenuated as a function of the menstrual-cycle phase of females.

Physiologic observations in a controlled clinical trial of the antiemetic effectiveness of 5, 10, and 15 mg of delta 9-tetrahydrocannabinol in cancer chemotherapy. Ophthalmologic implications

One hundred twenty patients about to receive their first treatment with potentially nauseant cancer chemotherapy were randomized to one of six antiemetic treatments: (1) no treatment; (2) placebo; (3) prochlorperazine (PCPZ), 10 mg; (4) delta 9-tetrahydrocannabinol (THC), 5 mg; (5) THC, 10 mg; (6) THC, 15 mg. Four doses of each medication were given orally at 4-hour intervals starting 2 hours before chemotherapy. A study nurse was responsible for both objective (nurse) and subjective (patient) symptom questionnaires. Serum levels were obtained at intervals for cross-reacting cannabinoids. Physiologic measurements including intraocular pressure (IOP), blood pressure, and pulmonary function were also recorded. In summary, the patients were remarkably free of adverse physiologic effects. All intraocular pressures before and after treatment were within the normal range, although a surprising statistically significant increase in IOP occurred in the group receiving 5 mg THC.

Relationship between plasma delta-9-tetrahydrocannabinol concentration and pharmacologic effects in man

The relationship between each of two pharmacologic effects (tachycardia and psychological "high") of delta-9-tetrahydrocannabinol (THC) and plasma THC concentration was investigated in three male and three female experienced marihuana smokers. Each subject smoked 1% THC cigarette on two occasions separated by 2 h. Heart rate and subjective psychological self-rating were determined frequently throughout the 4 h study period. Data were analyzed by calculating the area under the parameter versus time curves, constructing hysteresis plots, and calculating the decay rate constants from pharmacologic effect versus time plots. In both males and females, dose inhaled and psychological response were apparently equivalent for the first and second cigarettes. While all subjects exhibited marked tachycardia in response to the first cigarette, heart rate in both male and female subjects was not increased as markedly during the second cigarette. Interestingly, female subjects had less tachycardiac response than males during the second cigarette. Hysteresis plots revealed that both heart rate and subjective psychological effect were elicited in an effect compartment which was "deep" relative to the reference plasma compartment. The time courses of tachycardiac and psychological responses lagged behind the plasma THC concentration-time profile. Zero-order decay rate constants for subjective psychological rating did not change substantially from the first to second cigarette. This study suggest that plasma THC concentration is a poor predictor of simultaneously occurring physiological and psychological pharmacologic effects.

The triple effect induced by delta 9-tetrahydrocannabinol on the rat blood pressure

The intravenous injection of delta 9-tetrahydrocannabinol (2-10 mg/kg) produced dose-related changes in the rat blood pressure. Three effects were detected: (1) an immediate and short-lasting hypotension related to bradycardia, blocked after atropine, vagotomy hexamethonium and pithing; (2) A rise in blood pressure 30 seconds after injection, insensitive to yohimbine, hexamethonium, pithing and reserpine treatment; (3) a slow and persistent hypotension, 5 min later, insensitive to atropine and vagotomy but inhibited by hexamethonium, pithing and reserpine treatment. It was concluded that intravenous injection of THC in rats may induce vagal stimulation and hypotension. This effect was reversed and followed by hypertension due to direct vasoconstriction not dependent on sympathetic activity. After this action a central decrease in sympathetic tonus led to a persistent hypotension an effect which is commonly reported for mammals.

Myocardial infarction and marijuana

Myocardial infarction in the virtual absence of risk factors occurred in a 25-year old man shortly after smoking a cigarette containing marijuana. Subsequent coronary arteriography was normal.

The effect of marihuana intoxication on blood pressure

Forty-eight experienced marihuana smokers were assigned to one of four groups: coltsfoot, placebo, low dose marihuana and high dose marihuana. While both marihuana groups showed significant increases in subjective ratings of intoxication and pulse rate, blood pressure readings were unaffected or showed a modest decrease. This latter finding is discrepant with previous studies and is explained in terms of a drug X person interaction present in those studies.

Short-term effects of smoked marihuana on left ventricular function in man

The short-term effects of smoking one to three marihuana cigarettes (900 mg of marihuana per cigarette; 2.2% delta9-tetrahydrocannabinol) on left ventricular performance were evaluated in 21 experienced users of cannabis at different times during a 94-day in-hospital study of the biologic effect of daily heavy smoking of marihuana. In six subjects, cardiac output was determined using the indocyanine-green dye-dilution technique; and in two of these individuals and 15 additional subjects, cardiac output, ejection fraction, preejection period (PEP), left ventricular ejection time (LVET), and the velocity of circumferential fiber shortening (Vcf) were determined using echocardiograms, phonocardiograms, and carotid pulse recordings. Following the smoking of one to three marihuana cigarettes, the heart rate rose 16 to 53 percent, cardiac output rose 4 to 9 percent, stroke volume did not change or fell slightly, and ejection fraction, PEP/LVET, and did not change, except for a slight increase in Vcf (15%) after three marihuana cigarettes, which could be accounted for by the associated increase in heart rate (53%). These findings suggest that in long-term heavy users of cannabis, marihuana has no significant effect on myocardial contractility independent of its effect on heart rate.

Cardiovascular effects of delta9-tetrahydrocannabinol in conscious and anaesthetized dogs

1. Temporal effects of delta9-tetrahydrocannabinol (THC) on heart rate and blood pressure in conscious dogs were compared to those in anaesthetized dogs. 2. In conscious dogs, THC in doses of 0.25 and 0.1 mg/kg resulted in maximal heart rate reductions of 48 and 41%, respectively, and in no significant change in blood pressure. 3. In anaesthetized animals THC in doses of 0.5 and 0.25 mg/kg caused a peak reduction in heart rate of 38 and 34%, and of blood pressure of 24 and 8%, respectively. 4. The results demonstrate that the bradycardia in response to THC in dogs is independent of the concomitant anaesthesia. 5. We conclude that the discrepancy between heart rate response to THC in dogs and in man is due to a species difference.

Dose-related heart-rate, perceptual, and decisional changes in man following marihuana smoking

Information processing was tested in 12 male subjects after smoking marihuana containing 0, 10, or 20 mg. of delta-9-tetrahydrocannabinol (THC) in three consecutive experimental sessions according to a Latin square protocol. Successful dose control was indicated both by the dose-related linear increase observed in heart rate and by preliminary assays of THC metabolites excreted in the urine. During tachistoscopic presentation of varying numbers of circles, statistically significant decrements in information processing occurred as a function of THC dosage. However, adding irrelevant information (triangles) to the display of circles eliminated effects of marihuana on accuracy of counting. Complex reaction times for oddity discrimination increased significantly only after the high dose. Nonetheless, both the social and high doses inappropriately inhibited the general tendency to respond to changing stimuli during oddity discrimination. Marihuana had no effect on field-dependence as measured by the Rod-and-frame test.

Interactions between delta9-tetrahydrocannabinol and phencyclidine hydrochloride in rats

delta9-Tetrahydrocannabinol (THC; 2.5, 5.0, 10.0 mg/kg, PO) impaired avoidance and rotarod performance, and caused bradycardia and hypothermia. Phencyclidine (PCP; 1.25, 2.5, 5.0 mg/kg, IP) impaired avoidance and rotarod performance and caused a marked increase in photocell activity. When combined, the depressant properties of each drug were enhanced and the stimulation of photocell activity cg/kg THC and its interactions with PCP followed subacute treatment for six days, whereas many of the effects of PCP were enhanced after subacute treatment with a dose of 2.5 mg/kg. Open-field behavior was affected by each drug alone and in combination in a similar way as photocell activity, but the depression caused by their interaction was greater; both drugs caused an increase in urination. Response rates on an FR-10 schedule of food reinforcement were decreased by 2.5 mg/kg PCP, but not by 5.0 mg/kg THC; the combination caused greater response suppression than either drug alone. The functional interactions between THC and PCP were not related to changes in the concentrations of 14C or 3H in plasma or brain derived from 14C-delta9-THC and 3H-PCP, respectively.

The effects of delta-9-tetrahydrocannabinol (cannabis) on cardiac performance with and without beta blockade

Systolic time intervals (STI) were measured in ten healthy male volunteers before and after intravenous (i.v.) administration of 25 mug/kg delta-9-tetrahydrocannabinol (delta-9-THC). Mean +/- SEM heart rate increased 32 +/- 7 beats/min, while systolic and diastolic blood pressures were unchanged after delta-9-THC. Total electromechanical systole lengthened 17 +/- 4.2 msec, left ventricular ejection time (LVETc) prolonged 24 +/- 4.0 msec and pre-ejection period (PEP) shortened 17 +/- 5.1 msec after delta-9-THC. All of these changes were significant (P less than 0.01). In nine other subjects who underwent prior beta adrenergic blockade, similar but less marked changes were noted in heart rate, blood pressure, and STI after delta-9-THC. The shortening of PEP after delta-9-THC was only 9 msec (NS) in beta blocked subjects. Thus, delta-9-THC significantly increased heart rate, shortened PEP and prolonged LVETc without any change in afterload. Beta adrenergic blockade prevented significant shortening of PEP and blunted other responses. These findings suggest that delta-9-THC enhanced cardiac performance. Partial inhibition of this effect was achieved with prior beta adrenergic blockade.

Medical implications of marijuana use

The effect of marijuana smoking was studied in 28 healthy young adult men who had previously smoked marijuana for approximately 5 years each. The subjects were hospitalized on a closed research ward for 31 days during which comprehensive psychological, physiological, and medical observations and tests were done. Physical examinations, neurological examinations, chest X-rays, electrocardiograms, and clinical laboratory tests were all within normal limits. Marijuana produced inconstant changes in pulse rate and blood pressure in these studies. Six subjects were found to have significant reduction in resting vital capacity during the baseline period of the study which were felt to be related to their prior marijuana smoking. In contradistinction to these findings, 12 of 15 subjects had statistically significant increases in peak expiratory flow rate immediately following marijuana smoking. Body temperature tended to be slightly reduced during marijuana use.

Marihuana and the cardiovascular system

The actions of marihuana on the cardiovascular system in man are the most consistent physiological effects produced by acue administration. Significant tachycardia and conjunctival injection are well established effects. When the subject is upright, marihuana produces a fall in blood pressure; however, either no significant effect or a slight increase in blood pressure occurs when the subject is supine. Marihuana has been reported to increase limb blood flow and produce no significant effect on electrocardiogram of normal subjects. It, however, interferes with the integrity of peripheral vascular reflex responses. Although the detailed mechanism of action has not been elucidated, there is evidence that marihuana produces both sympathetci nervous system stimulation and parasympathetic nervous system blockade. No data are available that indicate the acute administration of marihuana presents a significant hazard to the cardiovascular system of normal subjects.