Taking Phentermine with MAO Inhibitors

Phentermine, like other prescription drugs, should not be taken with certain other prescription and over-the-counter medications. For this reason, when you are discussing the use of Phentermine for your weight loss, it is exceptionally important that you tell your doctor about any other medicines or supplements that you may be taking, as well as any medical conditions you may have. This will provide your doctor with a more complete understanding of your health needs and whether or not Phentermine use will suit those needs.

Taking phentermine with MAO inhibitors can cause severe side effects including primary pulmonary hypertension and cardiac valvular lesions.

One important example of the type of drug that cannot be taken alongside Phentermine is monoamine oxidase (MAO) inhibitors. These are drugs that are often prescribed in order to help treat anxiety disorders, depression, panic disorders, as well as other issues not listed here. Examples of MAO inhibitors are tranylcypromine (Parnate), phenelzine (Nardil), selegiline (Emsam and Eldepryl), isocarboxazid (Marplan), rasagiline (Azilect).

Not only should you not be taking these drugs, but you should not have been taking them over the last fourteen days (at least) before starting to take Phentermine, as MAO inhibitors can remain within the body for a couple of weeks and need some time to be cleared from the system. If MAO inhibitors are still within the body when Phentermine is taken, serious and potentially life-threatening side effects can result.

Since the 1970’s it has been known that Phentermine has the ability to hinder the process of MAO inhibitors when they metabolize serotonin, though it has never actually been labeled as an MAO inhibitor itself. For many years it was used in conjunction with other products and drugs designed to block serotonin uptake and re-uptake, though it was technically in violation of the labeling (also known as off-label use). It is now known that Phentermine does indeed interact with those drugs in a conflicting way and therefore your doctor and/or pharmacist should advise you against using Phentermine if you are taking any MAO inhibiting drugs. Remember, though, that your health is your own responsibility, so it is up to you to tell these professionals if you are taking MAO inhibitors in order to provide them with the information they need to properly advise you.

The greatest care needs to be taken when Phentermine is prescribed alongside other unlabeled MAO inhibitors. Like Phentermine, there are other drugs and supplements that cause MAO inhibition, but are not technically labeled as such. There are also a number of herbal products that act as MAO inhibitors. Doctors and pharmacists should double-check any of the medications or herbal supplements you may be taking before providing you with Phentermine. Again, it is up to you to disclose all this information.

Potential results of the conflict of these drugs can be dramatic and additive. They include primary pulmonary hypertension (a life-threatening lung disease) and cardiac valvular lesions (lesions within the heart valves).