Here are answers to some frequently asked questions about phentermine.
Does phentermine cause different side effects in females and males?
Not typically. Phentermine’s side effects don’t typically differ between females and males.*
However, phentermine can sometimes cause sexual side effects that could differ between males and females. For example, in males, phentermine can sometimes cause erectile dysfunction.
Sexual side effects typically go away after you stop taking the medication. If you’re concerned about sexual side effects with phentermine, talk with your doctor.
* Sex and gender exist on spectrums. Use of the terms “male” and “female” in this article refers to sex assigned at birth.
Can phentermine, including the 30 mg strength, cause long-term side effects?
It’s not likely. You’ll typically take phentermine for only a few weeks. If you have side effects with the dosage you take, these typically get better soon after you stop taking the medication.
However, on rare occasions, phentermine can cause heart valve damage. This could lead to long-term heart problems.
Long-term treatment with phentermine is not recommended. Your doctor will typically prescribe phentermine for only a few weeks to minimize the risk of serious side effects. These include heart valve problems, as well as certain other side effects.
For example, long-term treatment could raise your risk of mental health concerns such as psychosis (losing touch with reality). It could also lead to dependence on the medication. With dependence, you rely on the medication to function as it typically does, either physically or mentally.
If you’re concerned about your risk of side effects with the dosage of phentermine you’re prescribed, or the length of time your doctor prescribes it for, talk with your doctor.
How does phentermine work?
It’s not fully understood how phentermine works to help you lose weight. The drug affects various chemical messengers in your brain. One of its effects is to reduce your appetite, so you feel less hungry. This can make it easier to consume fewer calories, which can lead to weight loss. However, the drug may also have other effects on your metabolism that help lead to weight loss.
Phentermine’s effects in your body last for about 20 hours after you stop taking it. This is the drug’s half-life. A drug’s half-life describes how long it takes for your body to expel half a dose of the medication.
To maintain weight loss, it’s important to continue to follow your diet and exercise plan after stopping phentermine.
Is phentermine similar to Adderall? Can phentermine be used for ADHD?
Adderall is a stimulant medication that contains the active drugs amphetamine and dextroamphetamine. It’s used to treat attention deficit hyperactivity disorder (ADHD).
Phentermine is related to Adderall. However, it’s not used to treat ADHD. It’s not approved by the Food and Drug Administration (FDA) for this use, and doctors don’t typically prescribe it off-label for this use. It hasn’t been studied for ADHD and it’s not known if it’s effective for this use.
To find out about treatment options for ADHD, talk with your doctor.
How does phentermine compare with other similar drugs, such as Contrave or Qsymia?
Other medications are available to help weight loss. Some of these have been approved by the FDA, while others may be prescribed off-label. (With off-label use, a drug is prescribed for a use other than that approved by the FDA.)
Along with phentermine, other drugs that are FDA-approved to help with weight loss in certain adults who have overweight or obesity include:
All these medications reduce your appetite and help you consume fewer calories. Contrave can also help manage feelings of pleasure you get when eating. This can help you manage food cravings. Unlike phentermine, these drugs are all approved for long-term use.
Phentermine, Contrave, and Qysmia are all oral treatments. Wegovy and Saxenda are subcutaneous injections.
Other drugs that doctors sometimes prescribe off-label to help with weight loss include topiramate (Topamax) and bupropion (Wellbutrin). Topiramate is also prescribed off-label for binge eating disorder.
To learn more about how phentermine compares with other weight loss medications, talk with your doctor. They can help you determine the treatment option that’s right for you.