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There are many other medicines that can cause serious or life-threatening medical problems if you take them together with phenelzine. Do not take phenelzine before telling your doctor about all other prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Keep a list with you of all the medicines you use and show this list to any doctor, dentist, or other healthcare provider who treats you.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any new or worsening symptoms such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Stop using phenelzine and call your doctor at once if you have any of these serious side effects:

• sudden and severe headache, rapid heartbeat, stiffness in your neck, nausea, vomiting, cold sweat, sweating, vision problems, sensitivity to light;

• chest pain, fast or slow heart rate;

• swelling, rapid weight gain;

• agitation, unusual thoughts or behavior; or

• feeling light-headed, fainting.

Less serious side effects may include:

• dizziness;

• feeling weak or drowsy;

• sleep problems (insomnia);

• constipation, upset stomach;

• dry mouth, decreased urination; or

• impotence, difficulty having an orgasm.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.