Phentermine Side Effects

Brand Names: Adipex-P, Ionamin

Please note - some side effects for Phentermine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Phentermine - for the consumer

Phentermine

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Phentermine:

Bad taste in mouth; changes in sex drive; constipation; diarrhea; difficulty sleeping; dizziness; dry mouth; exaggerated sense of well being; headache; impotence; nervousness; overstimulation; restlessness; sleeplessness; upset stomach.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); bizarre behavior; chest pain; fainting; fast heartbeat; pounding in the chest; shortness of breath; swelling of the legs and feet; tremor.

Phentermine Resin

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Phentermine Resin:

Bad taste in mouth; constipation; diarrhea; difficulty sleeping; dizziness; dry mouth; exaggerated sense of well being; headache; nervousness; overstimulation; restlessness; sleeplessness; upset stomach.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); bizarre behavior; changes in sex drive; chest pain; decreased sexual ability; fainting; fast or irregular heartbeat; mental or mood changes; pounding in the chest; shortness of breath; swelling of the legs and feet; tremor.

For the professional

Phentermine

Cardiovascular: Primary pulmonary hypertension and/or regurgitant cardiac valvular disease, palpitation, tachycardia, elevation of blood pressure.

Central Nervous System: Overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, rarely psychotic episodes at recommended doses.

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

Allergic: Urticaria.

Endocrine: Impotence, changes in libido.

By body system

Cardiovascular side effects

Cardiovascular adverse effects may be associated with phentermine. Phentermine generally causes a significant rise in heart rate. Hypertension and arrhythmias may be problematic in susceptible patients. Valvular heart disease has been reported in patients taking phentermine in combination with fenfluramine or dexfenfluramine, but not in patients taking phentermine alone. Analysis of available data suggests that fenfluramine and dexfenfluramine are the causal agents, and both drugs have been withdrawn from the market as of September 15, 1997.

A 37-year-old woman was admitted to the hospital after an episode of ventricular fibrillation. The patient was being treated for moderate obesity and had been taking phentermine hydrochloride, thyroid (USP), and trichlormethiazide. Her previous medical history had been unremarkable. It was suspected that one or more of her medications contributed to the nearly fatal arrhythmia.

Two case reports describe patients using phentermine (one in combination with phendimetrazine) who later developed ischemic cerebrovascular disease. One suffered a cerebral infarct with angiographic evidence of vasculopathy involving multiple vascular beds. The other patient developed headache and a hemisensory disturbance of seven days duration.

A case of fatal pulmonary hypertension has also been reported in a 29-year-old woman 8 months following the use of fenfluramine (of which dexfenfluramine is the dextro isomer) and phentermine for only 23 days. Histopathological findings upon autopsy indicated severe pulmonary hypertension. She did not smoke and had no family history of pulmonary hypertension. No obvious risk factors other than obesity were present, although preexisting disease was not ruled out.

A case of restrictive cardiomyopathy due to endocardial fibrosis after short term use of fenteramine in combination with phentermine has been reported.

Nervous system side effects

Phentermine produces nervous system stimulation, which may result in tremor, anxiety, restlessness, dizziness, insomnia, euphoria, dysphoria, and headache.

Fifty women with refractory obesity received phentermine resinate for a period of 20 weeks. Three defaulted from the study due to incapacitating headaches without significant change in blood pressure. Two additional patients defaulted due to complaints of irritability.

A double-blind clinical trial of phentermine and fenfluramine involving 81 people with simple obesity reported several CNS complaints from patients taking phentermine resin during the study (twenty six complaints during the first 6 weeks of the study). The number of complaints diminished with time over the course of the study. Only seven complaints of CNS effects were reported at 20 weeks. Complaints reported by patients include sleep difficulties, nervousness, depression, fatigue and increased dreaming.

Psychiatric side effects

Rarely psychotic episodes have been reported at recommended doses with some sympathomimetic drugs.

Gastrointestinal side effects

Gastrointestinal adverse effects may include dryness of the mouth, unpleasant taste, diarrhea, and constipation.

Dermatologic side effects

An allergic reaction resulting in urticaria may occur.

Endocrine side effects

Endocrine effects such as impotence and changes in libido may occur in patients taking phentermine.

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