Is It Safe to Drink Caffeine While Taking Phentermine?
Phentermine (Adipex-P, Lomaira) is a weight loss medication from the stimulant class of drugs, PubChem says. Caffeine, whether naturally occurring in foods or synthetic, is also a stimulant that works on the central nervous system like phentermine, MedlinePlus says. Caffeine and phentermine interact with each other — combining the two can increase the risk or severity of side effects.
Understanding how caffeine interacts with phentermine allows you to use both substances more safely. To prevent harmful outcomes, consult your physician before using phentermine with caffeine.
Phentermine is a central nervous system stimulant medication prescribed as a temporary weight loss aid, PubChem says. When combined with a reduced-calorie diet and regular exercise, phentermine helps jump-start weight loss by suppressing your appetite. It’s a controlled substance in the United States because it has the potential to be misused, and it’s approved for use for up to 12 weeks, the Mayo Clinic says. (There’s also a version of phentermine combined with the anti-seizure drug topiramate, sold under the brand name Qsymia, that’s approved for longer-term use for weight loss.) Phentermine is available as tablets and extended-release capsules and is generally prescribed for short periods of three to six weeks, MedlinePlus says.
Caffeine is also a central nervous system stimulant that has many of the same side effects as phentermine, MedlinePlus says. It can be found naturally in foods and beverages like coffee, tea, and chocolate, or as an additive in many common items such as energy drinks and caffeinated sodas. It’s also sold over-the-counter in pill form, either alone or added to other medications, such as pain relievers and cold medicines.
Phentermine can cause adverse reactions in some users. Less serious side effects include dry mouth, an unpleasant taste, diarrhea, constipation, and vomiting, MedlinePlus says, though these can become severe or ongoing, requiring medical attention.
More serious adverse effects include:
Combining phentermine with other stimulants can increase the risk of developing certain side effects or make them more severe, according to PubChem. This includes caffeine. Taking the two substances together may result in potentially serious adverse reactions, due to their similar effects on the cardiovascular and nervous systems.
Cutting out caffeine and other stimulants while taking phentermine is the surest way to prevent side effects. If you can’t cut out caffeine entirely, PubChem advises that it should be limited.
Since stimulants affect people differently, there’s no specific recommendation for how much caffeine may be tolerable. Talk to your doctor about the safety of combining phentermine and caffeine, especially if you have high blood pressure or another cardiovascular condition. It may take some trial and error to find out how much caffeine your body can tolerate once you’re cleared to keep it in your diet.
Substituting drinks such as decaffeinated coffee and herbal tea for caffeinated beverages can help reduce your daily caffeine consumption. Since caffeine is present in many foods, medications, and supplements, read ingredient labels closely to determine which items contain the substance. Monitoring your blood pressure, heart, and respiration rate after consuming phentermine and caffeine can help you determine how they affect your body. Stop using phentermine and caffeine and seek prompt medical attention if you develop chest pain, high blood pressure, a rapid heartbeat, or other serious side effects.
The effects of caffeine and phentermine differ from person to person. Not all people who combine caffeine and phentermine will experience adverse reactions. While small amounts may not be harmful, you may need to avoid caffeine altogether if you’re sensitive to its effects.
When starting a new medication, always talk to your doctor or pharmacist about medication interactions with foods, beverages, and active ingredients like caffeine.
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