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Last reviewed on RxList: 4/4/2017
Ionamin Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 2/19/2016

Ionamin (phentermine resin) is a stimulant used together with diet and exercise to treat obesity (overweight) in people with risk factors such as high blood pressure, high cholesterol, or diabetes. The brand name Ionamin is discontinued, but generic versions may be available. Common side effects of Ionamin (phentermine resin) include dizziness, dry mouth or unpleasant taste in the mouth, difficulty sleeping (insomnia), irritability, restlessness, hyperactivity, nausea, vomiting, diarrhea, constipation, headache, tremors, increased or decreased interest in sex, or impotence.

The dose of Ionamin is one capsule daily, before breakfast or 10-14 hours before retiring. Ionamin may interact with blood pressure medications, insulin or oral diabetes medications, guanethidine, or antidepressants. Tell your doctor all medications and supplements you use. Ionamin must not be used during pregnancy. It may harm a fetus. If you are pregnant or think you may be pregnant, tell your doctor. This drug may pass into breast milk and could have undesirable effects on a nursing infant. Breastfeeding is not recommended while using this drug. Withdrawal symptoms may occur if you suddenly stop taking this medication.

Our Ionamin (phentermine resin) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Ionamin Consumer Information

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

Call your doctor at once if you have a serious side effect such as:

  • feeling short of breath, even with mild exertion;
  • chest pain, feeling like you might pass out;
  • swelling in your ankles or feet;
  • pounding heartbeats or fluttering in your chest;
  • confusion or irritability, unusual thoughts or behavior;
  • feelings of extreme happiness or sadness; or
  • dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, chest pain, shortness of breath, uneven heartbeats, seizure).

Common side effects may include:

  • feeling restless or hyperactive;
  • headache, dizziness, tremors;
  • sleep problems (insomnia);
  • dry mouth or an unpleasant taste in your mouth;
  • diarrhea or constipation, upset stomach; or
  • increased or decreased interest in sex, impotence.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Ionamin (Phentermine Capsules)

Ionamin Professional Information


Cardiovascular: Primary pulmonary hypertension (see WARNINGS), palpitation, tachycardia, elevation of blood pressure.

Central Nervous System: Overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache; rarely psychotic episodes at recommended doses with some drugs in this class.

Gastrointestinal: Dryness of the mouth, unpleasant taste, diarrhea, constipation, other gastrointestinal disturbances.

Allergic: Urticaria.

Endocrine: Impotence, changes in libido.

Read the entire FDA prescribing information for Ionamin (Phentermine Capsules)

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© Ionamin Patient Information is supplied by Cerner Multum, Inc. and Ionamin Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.