Mixing alcohol and phentermine is dangerous because one is a sedative and the other a stimulant. So their joint effect on the brain is hard to predict. Together they raise blood pressure and strain the heart. They raise the risk of heart attack and stroke. Alcohol also boosts appetite, which undoes phentermine’s weight loss.
Alcohol is a mind-altering substance found in large amounts in some common drinks. Even so, people have long used alcohol to lift their mood and ease social contact. It may even be good for health in small amounts. But very few people are likely to stick to the recommended limit of a drink or two a day.
On the other hand, a significant number of people abuse alcohol regularly. Many people are dependent on alcohol. And it is not rare for some people to combine alcohol with various mind-altering substances.
How does alcohol affect the brain?
Alcohol is fairly safe. It causes severe side effects only when people drink large amounts too often. But mixing alcohol with some synthetic drugs is a bad idea. After all, people may have long consumed alcohol, but they have not mixed it with synthetic drugs.
Why is it so dangerous to mix alcohol with other mind- or mood-altering drugs? One reason is that they might have opposite and often unpredictable effects.
Alcohol is a sedative, much like other common medications. But it does not sedate in small amounts. That is because it tends to hold back inhibitory neurons first. These are brain cells that put the brakes on activity. So small amounts may end up causing hyperexcitation (overexcitement). Its sedative effect becomes clear when people drink larger amounts.
How does phentermine affect the brain?
Phentermine works in the opposite way to alcohol. It is a stimulant, not a suppressant, much like amphetamines. In small doses, it lifts mood and focus and cuts sleep. More important, it cuts appetite.
Phentermine is a medical drug approved mainly to treat obesity. It is especially good for people with severe obesity plus diabetes, hypertension (high blood pressure) and other severe metabolic changes.
Used alone, it is fairly safe but not free from side effects. It may cause agitation, glaucoma and worsening heart disease in many people. It is also a bit addictive because of its effect on mood.
It has clear contraindications (reasons not to use it). The main ones are heart disease or a risk of it, poor blood pressure control, glaucoma, agitation and past drug abuse.
What happens when you mix phentermine and alcohol?
As you might guess, these two substances work very differently and act on different brain centers. One is a suppressant and the other a stimulant. So the final effect of combining them is unpredictable. That is why combining such different substances is a bad idea.
Of course, combining them at lower doses may not cause significant problems, since both may raise excitement and energy. But with higher doses of alcohol, things may change. The result can be a very unpleasant experience.
But it is not just about an unpleasant experience. Combining medications with alcohol is never a good idea. Alcohol is terrible for the liver, and it can also change how the body breaks down drugs.
At higher doses, the two substances try to cancel each other out. This has an unpredictable effect on the brain. And without doubt, it raises toxicity.
Besides, drinking alcohol while trying to lose weight is never a good idea. In many people, alcohol increases appetite, so phentermine may fail to help them lose weight. Also, some common alcoholic drinks are high in sugar. Alcohol addiction treatment can be key for people who struggle with alcohol dependency. It helps them live a healthier life and improves their chances of managing their weight.
Is mixing phentermine and alcohol bad for your heart?
But the most important reason not to mix them is the harm to the heart. True, a small amount of alcohol is not harmful to the heart, but it is a double-edged sword. More than two drinks is quite bad for heart health.
So combining alcohol and phentermine may make blood pressure worse. It may also put more stress on the heart muscle. All this considerably raises the risk of a heart attack. Also, people with obesity are less likely to have a healthy heart. Combining them also raises the risk of stroke1,2.
Does alcohol stop phentermine from working for weight loss?
Phentermine is mainly a weight loss drug. So a person taking it regularly on a doctor’s prescription is quite likely using it to lose weight. But alcohol has the opposite effect. It may stimulate appetite. So it blocks phentermine’s action, making it almost ineffective.
Of course, other factors matter too. For example, some people may like the effect of using these substances together. But using phentermine and alcohol raises the risk of addiction to both, and so the risk of side effects.
As a stimulant, phentermine can cause a high at higher doses. It may mix well with some alcohol. But mixing phentermine with a lot of alcohol causes an unpleasant feeling and blocks the high.
In short, phentermine is a weight loss drug that also stimulates the brain and mood. So using it with alcohol may be addictive. But the two work against each other at higher doses, so the combination is bad in every way. It also considerably raises the risk of cardiovascular (heart and blood vessel) problems.
Frequently asked questions
Can you drink alcohol while taking phentermine?
It is a bad idea. Phentermine is a stimulant and alcohol is a sedative. So together their effect on the brain is hard to predict. With more alcohol, the two fight each other, toxicity goes up and the experience turns unpleasant. The mix also raises blood pressure and puts stress on the heart muscle. It raises the risk of heart attack and stroke.
What should you not mix with phentermine?
Alcohol is the big one. Mixing any medication with alcohol is a bad idea. That is because alcohol is hard on the liver and changes how the body breaks drugs down. Phentermine also is not for everyone. Its main contraindications are heart disease or a risk of it and poorly controlled blood pressure. Glaucoma, agitation and a history of drug abuse are on the list too.
Can you drink alcohol on weight loss medication?
Drinking works against weight loss. In many people alcohol increases appetite, which can leave phentermine almost ineffective. Many common alcoholic drinks are also high in sugar. Using the two together also raises the risk of getting addicted to both. For people who struggle to cut back, alcohol addiction treatment improves their chances of managing their weight.
Related reading
10 Signs Your Liver Is Detoxing from Alcohol · Alcohol dependence genes tied to rapid Alzheimer's · Heart Medicine for Alcohol Use Disorder: Spironolactone
References
1. Jordan J, Astrup A, Engeli S, Narkiewicz K, Day WW, Finer N. Cardiovascular effects of phentermine and topiramate: a new drug combination for the treatment of obesity. J Hypertens. 2014;32(6):1178-1188. doi:10.1097/HJH.0000000000000145
2. Kokkinos J, Levine SR. Possible association of ischemic stroke with phentermine. Stroke. 1993;24(2):310-313. doi:10.1161/01.STR.24.2.310