Beta blockers are prescribed for some of the most common cardiovascular conditions in medicine, including high blood pressure, coronary artery disease, heart failure, abnormal heart rhythms, and recovery after heart attack. Drugs in this class are also used for migraine prevention, essential tremor, performance anxiety, and several other conditions. At the same time, medicinal cannabis use has become increasingly common, making the combination of marijuana and beta blockers increasingly relevant to physicians, pharmacists, and patients. The central question is whether cannabinoids such as THC and CBD can change either the cardiovascular effects or the metabolism of beta-blocking medications.
The answer depends heavily on which beta blocker is involved and what kind of cannabis product is being used. THC can acutely increase heart rate and alter blood pressure, potentially working against some of the physiological effects beta blockers are intended to produce. CBD creates a different concern because laboratory studies show that it can inhibit CYP2D6, an enzyme responsible for metabolizing several important beta blockers, including metoprolol and carvedilol. Direct clinical trials of modern cannabis products with most beta blockers remain limited, but decades of human research—including controlled studies with propranolol and THC—provide useful evidence about how the two drug classes can interact.
How Beta Blockers Work
Beta blockers reduce the effects of adrenaline and related catecholamines by blocking beta-adrenergic receptors. Beta-1 receptors are concentrated in the heart, where their stimulation increases heart rate, contraction strength, and electrical conduction. Selective beta-1 blockers such as metoprolol and atenolol primarily target these cardiac receptors at ordinary therapeutic doses. Nonselective beta blockers such as propranolol block both beta-1 and beta-2 receptors, while carvedilol and labetalol additionally block alpha receptors and can therefore produce more direct vasodilation.
The overall result is usually a reduction in heart rate, blood pressure, cardiac workload, or some combination of these effects. FDA prescribing information for metoprolol, propranolol, carvedilol, and other beta blockers warns about adverse reactions such as bradycardia, hypotension, dizziness, fatigue, weakness, and, in susceptible patients, conduction abnormalities. These effects create the background against which cannabis must be considered. A cannabinoid product does not have to produce a dramatic metabolic interaction to matter clinically if it changes heart rate, vascular tone, dizziness, or blood pressure at the same time.
Cannabis Has Its Own Cardiovascular Effects
THC does not behave like a beta blocker. The American Heart Association‘s scientific statement on cannabis and cardiovascular health concluded that THC can activate the sympathetic nervous system, increase heart rate, raise myocardial oxygen demand, and alter blood pressure. Shortly after marijuana use, heart rate can rise substantially, particularly in people who are not tolerant to THC. Blood pressure can initially rise while standing blood pressure may later fall, contributing to orthostatic dizziness in some users. The response varies with THC dose, route of administration, tolerance, age, and cardiovascular health.
A 2024 analysis published in the Journal of the American Heart Association also found an association between cannabis use and adverse cardiovascular outcomes in U.S. adults, with more frequent use associated with greater odds of events such as myocardial infarction and stroke. Observational studies cannot prove that cannabis caused each event, and lifestyle and product differences complicate interpretation, but the findings reinforce why marijuana use is particularly relevant in people already being treated for cardiovascular disease.
Propranolol and THC Have Actually Been Studied Together
Unlike many cannabis-medication combinations, propranolol and marijuana have been examined directly in controlled human experiments. In a 1977 randomized clinical study, six experienced marijuana users received propranolol, marijuana containing approximately 10 milligrams of THC, or the two together. Marijuana alone produced the expected increase in heart rate and blood pressure along with subjective intoxication. Pretreatment with 120 milligrams of propranolol effectively blocked much of the cardiovascular response to marijuana.
Another controlled study examined THC’s effects on cardiac performance before and after beta-adrenergic blockade. THC increased heart rate and altered measurements reflecting cardiac contraction and performance. When participants were beta blocked beforehand, those effects were substantially blunted. Researchers concluded that part of THC’s acute cardiovascular response was mediated through sympathetic beta-adrenergic mechanisms. These studies are old, small, and used cannabis products that differ greatly from today’s high-potency flower and concentrates, but they remain important because they demonstrate a true physiological interaction in humans rather than merely a theoretical one.
Propranolol Does Not Make Marijuana Risk-Free
The fact that propranolol can suppress marijuana-related tachycardia should not be interpreted as evidence that taking a beta blocker makes THC safer. Propranolol blocked much of the cardiovascular stimulation in the early studies, but it did not simply eliminate cannabis pharmacology. In the 1977 experiment, propranolol also altered aspects of the subjective marijuana experience and cognitive response. Modern cannabis products can deliver substantially higher THC doses than those examined in early laboratory studies, particularly through concentrates and high-dose edibles.
Propranolol itself can cause slow heart rate, fatigue, dizziness, and hypotension. Cannabis may sometimes produce postural hypotension, meaning a person could experience a very different response after the initial THC-related increase in heart rate fades. Propranolol is also metabolized through several hepatic pathways, including CYP2D6, CYP1A2, and CYP2C19. FDA labeling shows that inhibitors of these enzymes can increase propranolol concentrations, creating another theoretical pathway through which cannabinoid products—particularly high-dose CBD—could influence treatment.
Cannabis and Metoprolol
Metoprolol deserves special attention because it depends heavily on CYP2D6 metabolism. FDA prescribing information states that metoprolol is predominantly metabolized by CYP2D6 and that strong CYP2D6 inhibitors can roughly double its concentrations. People who genetically metabolize CYP2D6 poorly also develop several-fold higher metoprolol concentrations than normal metabolizers. Increased exposure can intensify beta blockade, potentially producing excessive slowing of the heart, low blood pressure, fatigue, dizziness, or loss of the drug’s usual beta-1 selectivity at higher concentrations.
CBD has been shown experimentally to inhibit CYP2D6. Japanese researchers studying cannabidiol in human liver microsomes found it to be a potent direct inhibitor of CYP2D6 activity. A broader University of Arkansas review likewise identified both CBD and THC as inhibitors of CYP2D6 in laboratory models, although the authors emphasized that clinical confirmation remains much more limited than the laboratory evidence. The American Heart Association’s cannabis statement specifically lists metoprolol and carvedilol among beta blockers whose concentrations could theoretically increase when cannabinoid-mediated CYP2D6 inhibition occurs.
How Significant Is the Metoprolol-CBD Risk?
No large controlled trial has yet shown exactly how much a typical CBD oil, gummy, or cannabis flower product changes metoprolol blood concentrations in patients. That is an important limitation. Laboratory inhibition does not automatically translate into a clinically important interaction because cannabinoid doses achieved in the bloodstream vary widely. Someone occasionally using cannabis flower with minimal CBD exposure does not have the same pharmacological profile as someone consuming several hundred milligrams of oral CBD every day.
However, research on established CYP2D6 inhibitors demonstrates why the pathway matters. A 2025 review from Henry Ford Health and Michigan State University found that strong CYP2D6 inhibitors such as paroxetine and fluoxetine can increase metoprolol exposure by as much as eightfold, while moderate inhibitors can produce two- to threefold increases. A meta-analysis of 15 studies involving more than 1,100 participants also found that genetically poor CYP2D6 metabolizers experienced greater heart-rate and blood-pressure reductions and appeared to have more bradycardia while taking metoprolol. CBD has not been proven to reproduce these magnitudes, but CYP2D6 inhibition is therefore a clinically relevant mechanism rather than merely an academic concern.
Carvedilol, Atenolol, and Labetalol Are Different
Carvedilol also involves CYP2D6 metabolism. FDA labeling warns that potent CYP2D6 inhibitors are expected to increase concentrations of one carvedilol enantiomer, and people who metabolize CYP2D6 poorly experienced more dizziness during dose escalation in clinical trials. Because carvedilol lowers blood pressure through both beta blockade and alpha-1 blockade, excessive exposure could theoretically increase dizziness or hypotension. CBD-mediated CYP2D6 inhibition is therefore plausible as an interaction mechanism, although direct CBD-carvedilol clinical trials remain lacking.
Atenolol presents a different situation. FDA pharmacokinetic information shows that atenolol undergoes little or no liver metabolism and is eliminated primarily through the kidneys. CYP inhibition from CBD is therefore far less likely to change atenolol concentrations substantially. The more important cannabis-atenolol issue is probably pharmacodynamic: both can influence blood pressure, dizziness, exercise tolerance, and heart rate. Labetalol is similarly distinct because it is metabolized mainly through glucuronidation rather than CYP2D6. These differences show why the phrase “cannabis and beta blockers” cannot describe a single uniform drug interaction.
Could Cannabis Cause Excessively Low Blood Pressure?
One of the most practical concerns is hypotension rather than enzyme metabolism. Beta blockers reduce cardiac output and, depending on the drug, may also reduce vascular resistance. THC can initially increase sympathetic activity, but marijuana can also produce vasodilation and orthostatic hypotension. Someone taking a beta blocker may therefore experience lightheadedness, weakness, blurred vision, or faintness after standing, particularly with higher THC doses, dehydration, hot environments, alcohol, or additional blood-pressure medications.
This may be more significant in older adults, people with autonomic dysfunction, and patients taking combinations such as a beta blocker plus an ACE inhibitor, ARB, diuretic, calcium-channel blocker, or alpha blocker. Cannabis does not need to dramatically increase beta-blocker concentrations to push someone whose resting blood pressure is already low into symptomatic hypotension. Unexplained fainting, severe weakness, confusion, chest pain, or persistent very low blood pressure should receive medical evaluation rather than simply being attributed to a strong marijuana product.
What About Bradycardia?
THC commonly produces tachycardia immediately after exposure, but the cardiovascular response is not always one-directional. Higher doses, chronic use, changing autonomic responses, and individual susceptibility can produce bradycardia or hypotension in some circumstances. Beta blockers already slow the heart, so clinically significant bradycardia becomes a reasonable concern whenever additional factors suppress cardiac rate or conduction.
Symptoms of excessive beta blockade can include unusually slow pulse, fatigue, dizziness, exercise intolerance, fainting, shortness of breath, or confusion. People with preexisting conduction disease, sick sinus syndrome, or atrioventricular block may have less tolerance for additional heart-rate reduction. Cannabis should not automatically be blamed for every episode of bradycardia in someone taking a beta blocker, but major changes in THC or CBD use are worth discussing when previously stable heart-rate control suddenly changes.
THC and CBD Create Different Questions
THC’s most immediate interaction with beta blockers is usually cardiovascular and pharmacodynamic. It stimulates the sympathetic nervous system, frequently raises heart rate, and changes vascular tone. A beta blocker may blunt some of those changes, as the historical propranolol studies demonstrated. High doses can nevertheless produce anxiety, dizziness, altered perception, and changes in blood pressure that remain clinically relevant even when the pulse does not rise dramatically.
CBD typically causes much less intoxication, but its drug-metabolism profile can be more important. CYP2D6 inhibition creates a plausible interaction with metoprolol, carvedilol, propranolol, and several other beta blockers. A 2025 scoping review of 136 cannabinoid interaction studies identified hundreds of potential CBD-drug interactions, most involving pharmacokinetic mechanisms, but only a small percentage of the literature directly established clinical significance. The evidence therefore supports caution without pretending that every CBD user will develop excessive beta blockade.
Smoking Cannabis Adds Another Cardiovascular Variable
Route of use matters. Smoking marijuana exposes the cardiovascular system to combustion products in addition to THC. The American Heart Association has emphasized that cannabis smoke contains many of the same harmful components found in tobacco smoke and that inhaled cannabis can increase carbon monoxide exposure while simultaneously increasing cardiac workload. This combination is particularly relevant to people taking beta blockers for coronary artery disease or after a heart attack.
Edibles eliminate combustion but introduce different problems. Their effects are delayed and last much longer, increasing the possibility of accidental overconsumption. Someone taking another edible because the first appears ineffective may eventually experience a much larger THC exposure several hours later. Concentrated CBD preparations introduce still another pattern, with prolonged cannabinoid exposure that may be more relevant to liver-enzyme inhibition than a brief inhaled dose.
Who May Need Additional Caution?
People with resting bradycardia, low blood pressure, heart conduction disorders, advanced heart failure, kidney or liver disease, previous fainting episodes, or multiple cardiovascular medications should be particularly cautious. Someone taking metoprolol or carvedilol together with concentrated CBD has an additional theoretical metabolic interaction through CYP2D6. In contrast, someone taking renally eliminated atenolol may have less metabolic interaction risk but can still experience overlapping blood-pressure or dizziness effects.
Changes in cannabis use may be especially informative. Beginning daily CBD, switching to a high-potency THC concentrate, dramatically increasing edible doses, or abruptly stopping heavy cannabis use changes the pharmacological environment. Clinicians evaluating new dizziness, slow pulse, blood-pressure changes, or altered beta-blocker response should know about these changes. Beta blockers themselves should generally not be abruptly discontinued without medical guidance because withdrawal can produce rebound sympathetic activity, worsening angina, rapid heart rate, hypertension, or—in people with coronary disease—serious cardiac events.
Final Thoughts on Cannabis and Beta Blockers
Cannabis and beta blockers interact at two distinct levels. THC can directly alter the cardiovascular system by increasing sympathetic activity, heart rate, myocardial oxygen demand, and vascular changes. Controlled human studies performed decades ago showed that propranolol substantially blunted THC-related increases in heart rate and blood pressure, demonstrating that beta-adrenergic pathways contribute to marijuana’s cardiovascular effects. Those studies do not prove that beta blockers make marijuana safe; they simply establish that the drugs can physiologically oppose some of THC’s acute cardiovascular actions.
CBD raises a different concern. Laboratory studies show inhibition of CYP2D6, while metoprolol, carvedilol, propranolol, and several other beta blockers rely on that enzyme to varying degrees. The American Heart Association recognizes these interactions as plausible, but direct human studies measuring CBD’s effect on beta-blocker concentrations remain limited. Atenolol and labetalol are less dependent on CYP2D6 and therefore have different interaction profiles. For patients taking beta blockers, the most useful approach is to tell the prescribing physician or pharmacist what cannabis product is being used, approximately how much THC and CBD it contains, how frequently it is taken, and whether symptoms such as unusually slow heart rate, severe dizziness, fainting, or unexpected blood-pressure changes have developed. Cannabis use does not automatically require stopping a beta blocker, but the combination is sufficiently complex that individual medication, cannabinoid dose, cardiovascular history, and route of cannabis use all matter.
