Phentermine Adverse Reactions
- angina
- blurred vision
- cardiac valvulopathy
- constipation
- depression
- diarrhea
- dizziness
- dysgeusia
- dyskinesia
- dysphoria
- dyspnea
- EEG changes
- euphoria
- fatigue
- headache
- hypertension
- impotence
- insomnia
- irritability
- libido decrease
- libido increase
- mydriasis
- nausea/vomiting
- ocular irritation
- palpitations
- peripheral edema
- psychological dependence
- psychosis
- pulmonary hypertension
- restlessness
- sinus tachycardia
- syncope
- tolerance
- tremor
- urticaria
- xerostomia
Phentermine Adverse Reactions
Adverse reactions associated with phentermine can affect several organ systems. Nervous system adverse reactions include dizziness, dyskinesia, dysphoria, euphoria, headache, insomnia, overstimulation, restlessness, and tremor. Psychosis at recommended doses may occur rarely in some patients. Ocular adverse effects of phentermine include blurred vision, mydriasis, and ocular irritation. Cardiovascular adverse effects include hypertension, palpitations, and sinus tachycardia. Adverse gastrointestinal effects of phentermine include constipation, diarrhea, dysgeusia, nausea/vomiting, and xerostomia. Other adverse reactions include impotence, libido increase, libido decrease, and urticaria.
Tolerance to the anorexiant effects of phentermine usually develops within a few weeks of starting therapy. The mechanism of tolerance appears to be pharmacodynamic in nature; higher doses of phentermine are required to produce the same response. When tolerance develops to the anorexiant effects, it is generally recommended that phentermine be discontinued rather than the dose increased. The maximum recommended dose should not be exceeded.
Abuse of phentermine may be associated with intense psychological dependence and severe social dysfunction. In some cases, patients have increased the dose of phentermine several times that recommended. Abrupt withdrawal of phentermine after prolonged high doses may result in extreme fatigue or mental depression; sleep EEG changes have also been noted. Signs and symptoms of chronic use of anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity, and personality changes. Psychosis, which can often clinically indistinguishable from schizophrenia, is the most severe manifestation of chronic intoxication.
Primary pulmonary hypertension (PPH) or cardiac valvulopathy have been reported to occur in some patients receiving a combination of phentermine with fenfluramine or dexfenfluramine. The possibility of an association between PPH or valve abnormalities and the use of phentermine alone cannot be ruled out. The initial symptom of PPH is usually dyspnea. Other initial symptoms include: angina pectoris, syncope, or peripheral edema. Patients should be advised to report immediately any deterioration in exercise tolerance. Treatment should be discontinued in patients who develop new, unexplained symptoms of dyspnea, angina pectoris, syncope, or peripheral edema.
[ Last revised: 1/30/2002 ]
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