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Phentermine and Alcohol: Interactions, Effects & Dangers

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Drinking while taking phentermine can interfere with weight loss and put you at risk of severe side effects and drug interactions.

Phentermine is a common weight loss medication prescribed to more than 800,000 Americans annually. Alcohol is also a common and widely available substance making you wonder if it is safe to take your phentermine with alcohol. Because of a drug interaction between the two, it is important to understand the downsides of drinking if you take phentermine.

What Is Phentermine?

Phentermine (sold under brand names like Adipex-P, Ionamin, Phentride and Teramine) is a stimulant medication sometimes prescribed for weight loss. It is a Schedule IV controlled substance and works by suppressing your appetite.

Phentermine Side Effects

Phentermine’s side effects are similar to those of other stimulant drugs and include:

  • Headache
  • Dry mouth
  • Libido changes
  • Tremor
  • Overstimulation
  • Diarrhea or constipation
  • Insomnia
  • Rash
  • Rapid heart rate
  • High blood pressure
  • Psychosis
  • Pulmonary hypertension
  • Heart disease
  • Addiction

Is Phentermine Addictive?

Like other stimulants, phentermine has the potential for abuse, addiction and dependence and is classified as a controlled substance. Specifically, phentermine is a Schedule IV controlled substance, unlike other stimulants, which are often even higher risk at Schedule II. For this reason, you should only take phentermine exactly as prescribed and never take phentermine that you have not been prescribed.

Signs of Phentermine Abuse

When someone starts abusing phentermine, signs often become evident. These may include:

  • Unexpected weight loss
  • Taking phentermine in ways other than prescribed, like snorting or smoking the drug
  • Mixing the drug with other substances to try to enhance its effects
  • Going to different doctors or pharmacies to try to get phentermine
  • Trying to pay cash for phentermine at pharmacies so the drug will not be run through insurance
  • Exaggerating symptoms to try to get a phentermine prescription
  • Borrowing, buying or stealing someone else’s phentermine

Over the long term, chronic phentermine misuse can also lead to the following side effects:

  • Severe skin problems
  • Insomnia
  • Irritability
  • Hyperactivity
  • Personality changes
  • Psychosis

Showing signs of phentermine misuse means that it is time to seek help. Phentermine misuse can easily morph into a full-blown phentermine addiction and carries an overdose risk.

Phentermine Overdose Symptoms

An overdose of a stimulant like phentermine is a medical emergency. If you suspect someone has overdosed on phentermine, you should call 911. Symptoms of a phentermine overdose include:

  • Restlessness
  • Tremor
  • Stiff muscles
  • Rapid breathing
  • Confusion
  • Aggression
  • Hallucinations
  • Panic state
  • Heart rhythm abnormalities
  • Blood pressure changes
  • Nausea and vomiting
  • Diarrhea
  • Abdominal cramps
  • Seizure
  • Coma
  • Death

Phentermine Withdrawal Symptoms

When someone takes phentermine over the long term, the body becomes used to its presence and adapts accordingly. This means if you suddenly stop the drug, the body can be thrown off balance, leading to several withdrawal symptoms like:

  • Extreme fatigue
  • Depression
  • Changes in your brain waves on sleep tests

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Can You Drink Alcohol While Taking Phentermine?

You should avoid alcohol while taking phentermine. Alcohol and phentermine have a drug interaction and, when combined, can cause many side effects. Taking them together can even increase your chances of an alcohol overdose.

Side Effects of Mixing Phentermine and Alcohol

Mixing phentermine and alcohol can be problematic and even dangerous. Not only do the two substances carry a drug interaction, but combining them can counteract your weight loss journey on phentermine and even put you at risk of alcohol poisoning.

Alcohol Overdose Risk

While alcohol depresses the central nervous system, stimulants like phentermine rev it up. This stimulant side effect can mask some of the symptoms of alcohol intoxication that can make a person feel drunk or buzzed, increasing the risk of an alcohol overdose. In 2010, the FDA banned drinks containing alcohol and stimulants due to multiple cases of alcohol poisoning from this interaction.

Decreased Effectiveness of Phentermine

Alcohol can be counterproductive on your weight loss journey using phentermine. Alcohol contains a lot of calories, leading to weight gain. This is especially true if you drink mixed drinks. In addition, drinking alcohol may cause you to make poor nutritional choices, further compounding weight gain.

Gastrointestinal Issues

Phentermine and alcohol can cause gastrointestinal issues as side effects, including nausea and vomiting. Therefore, combining the two substances may put you at an even higher risk of experiencing these unpleasant side effects.

Cardiovascular Problems

Mixing alcohol and phentermine can be harmful to your cardiovascular system, causing symptoms like:

  • Increased heart rate
  • Chest pain
  • Blood pressure changes

Central Nervous System (CNS) Effects

Combining alcohol and phentermine can wreak havoc on your central nervous system, causing side effects like:

  • Dizziness
  • Drowsiness
  • Depression
  • Concentration problems

Help for Alcohol and Stimulant Abuse

If you struggle with phentermine and alcohol, quitting these substances can seem overwhelming. Fortunately, help for polysubstance abuse is available. At The Recovery Village at Baptist Health, we can help wean you off phentermine and alcohol in medical detox, followed by rehab to keep you substance-free for good. Contact a Recovery Advocate today to learn more.

View Sources “Phentermine: Package Insert .” March 22, 2023. Accessed April 9, 2023. “Phentermine Monograph for Professionals.” November 10, 2022. Accessed April 9, 2023.

National Library of Medicine. “Weight loss and alcohol.” June 22, 2022. Accessed April 9, 2023.

Centers for Disease Control and Prevention. “Alcohol and Caffeine.” December 7, 2022. Accessed April 9, 2023. “Drug Interaction Report: ethanol, phentermine.” Accessed April 9, 2023.

ClinCalc. “Phentermine – Drug Usage Statistics.” Accessed April 9, 2023.