Phentermine and Alcohol

Stimulants, such as amphetamines, stimulate the brain while depressants, such as alcohol, slow down parts of the brain. Mixing a stimulant and alcohol can have adverse effects on the body; and when that stimulant is a weight-loss pill, such as phentermine, the consequences can be high.

What Is Phentermine and How Does It Help With Weight Loss?

For those who are obese or who have medical problems regarding their weight, doctors may prescribe Adipex-P or Lomaira, which are brand names for the drug phentermine. Doctors usually only prescribe phentermine for those with a BMI (body mass index) over 30. Phentermine is the most widely prescribed weight-loss pill, and it was approved by the FDA in 1959.

Phentermine and Alcohol

Phentermine is in a class of drugs called anorectics, which are essentially diet pills. Anorectics were designed to replace amphetamines, but they produce a similar effect; anorectics are less potent than amphetamines, though.

The phentermine drug works by making you feel satiated and reducing hunger pangs. This effect reduces the risk of binging or overeating throughout the day.

When doctors prescribe phentermine, it should go hand in hand with an effective weight-loss program. The drug, itself, is for short-term use. Patients taking the drug should be slowly weaned off of it, and then encouraged to embrace a permanent lifestyle change with regard to their diet.

When patients are prescribed phentermine, they get it as a tablet. These extended-release capsules should be taken either once daily or three times a day half an hour before meals. It’s important that patients follow their doctors’ advice carefully as phentermine is an addictive drug.

Most patients have been prescribed phentermine for 3-6 weeks, though some are prescribed phentermine for 12 weeks. Additional studies have found that phentermine can be effective for weight loss for even longer periods if used carefully. However, it’s easy not to use phentermine carefully, and a tendency to abuse the drug does occur.

How Does Phentermine Work on Your Body?

Phentermine is a central nervous stimulant, which means the drug stimulates specific neurons in your body, pushing them to release neurotransmitters. In the case of phentermine, the drug activates the release of epinephrine or adrenaline in your body. Phentermine also seems to increase the body’s levels of leptin while reducing the effects of neuropeptide Y.


Epinephrine is the body causes an increase in heart rate, blood pressure, and muscle strength. Like adrenaline, the body releases the substance during a “fight or flight” response. An excess of epinephrine in the body leads to a higher metabolic rate, which translates into weight loss.


Leptin’s primary role in the body is to regulate how much you eat. It regulates your body’s energy and determines how much fat you store. If you have high levels of leptin, your body feels satiated. If you have low levels, your body feels hungry. Phentermine raises your leptin levels so that you feel satiated, thereby eating less.

Neuropeptide Y

Like leptin, the neuropeptide Y neurotransmitter affects how we eat. When the neurotransmitter is activated, you have a desire to eat. When reduced, your desire to eat diminishes.

By having the body release the above hormones and neurotransmitters, phentermine suppresses appetite and increases your body’s activity levels.

Why Is Phentermine a Schedule IV Drug?

To find out why phentermine is classified as a schedule IV drug, let’s look at how drugs are categorized.

Drug Scheduling

Drug scheduling is a way of categorizing drugs into their potential for abuse. There are five categories or schedules. A schedule I drug has a high potential for abuse while a schedule V drug has a much lower potential for abuse. Some schedule I drugs are heroin and peyote. Some schedule V drugs are cough medications with less than 200mg of codeine.

Phentermine is a schedule IV drug because it creates the same effects in the body as amphetamine. Although it has a somewhat low potential for abuse, this abuse can escalate if the drug is combined with other substances, such as alcohol. In addition, phentermine comes with side effects that can be dangerous. Some of the side effects include increased heart rate, heart palpitations, restlessness, insomnia, and tremors.

Anorectic drugs, like phentermine, tend to become less effective after a few months, and doctors attribute this to chemical alterations in the brain, due to continued use of the drug. As a result, those with substance use disorders may become addicted to phentermine. A less effective drug after a few weeks may encourage some people to take more than the required dose.

Effects of Mixing Phentermine and Alcohol

When you’re taking phentermine to lose weight, drinking alcohol can disrupt your weight goals. Alcohol is a downer, so it will reduce the effect of phentermine. This may make you increase your phentermine dosage, which can then lead to addiction. What’s more, alcohol doesn’t help you lose weight, and mixing the two can easily become self-defeating.

By itself, phentermine can be a dangerous drug if abused as it is classified as a stimulant with amphetamine-like effects. It’s addictive and it can lead to a stroke if abused. Stimulants affect your central nervous system, and if they are abused they can also cause damage to your tissues and organs.

On the other end, alcohol is a central nervous system depressant. One would think that the two would cancel each other out. Instead, the side effects of both are magnified. Alcohol increases the effects of phentermine. In addition, when you’re taking phentermine, it masks the effects of alcohol, leading you to drink more. This can lead to alcohol poisoning.

Effects of Alcohol on the Body

When you drink alcohol to excess on an almost daily basis, it will begin to take a toll on your health. Besides changing your mood and your behavior, communication to the brain’s pathways are inhibited, which is what accounts for the lack of memory the day after a night of heavy binge drinking. Worse, people who drink excessively for years can end up with cirrhosis, alcoholic hepatitis, or fibrosis.

Cardiovascular Effects

When you mix alcohol and an amphetamine-like drug, you’re putting a lot of strain on your heart. If your symptoms are mild, you may simply suffer from heart palpitations. More severe systems, however, can be a seizure or a stroke.

Gastrointestinal Issues

Because alcohol affects your stomach’s lining, mixing phentermine and alcohol can bring on heartburn, vomiting, intense stomach aches, and nausea.

Central Nervous System Effects

The combination of phentermine and alcohol can affect your central nervous system and make you dizzy and drowsy. It can also make it difficult to concentrate. More severe systems can lead to damaged organs.

If you want to drink, it’s important that you wait 12 hours after taking your phentermine pill, as an extended-release capsule lasts for 12 hours. Remember that both substances are addictive. When combined, you are doubling the likelihood of abusing both substances, which can lead to an unhealthy dependence on both. And if what you’re chasing is the high from combining a stimulant and alcohol, then you may have a substance use disorder.

Treating Addiction to Phentermine and Alcohol Abuse

If you have a substance use disorder, you’ll need to slowly taper off the amount of stimulant you’re taking along with reducing the amount of alcohol you’re drinking. Stopping both instantly can be negative and even life-threatening. Detoxing in a detox center is the safest way to detox.

If you need help recovering from a substance use disorder, reach out to us for help.


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