Phentermine

INTRODUCTION

Indications

Short-term treatment of obesity in conjunction with other interventions (dietary restriction, exercise); used to produce and maintain weight loss in patients with a BMI ≥30 kg/m² or ≥27 kg/m² in the presence of other risk factors (diabetes, hypertension, hyperlipidemia).

Action

Decreases hunger by altering the chemical control of nerve impulse transmission in the appetite control center of the hypothalamus. Therapeutic Effects: Appetite suppression with resultant weight loss.

Adverse Reactions/Side Effects

CNS: CNS stimulation, confusion, dizziness, dysphoria, euphoria, headache, insomnia, mental depression, restlessness. EENT: blurred vision. CV: hypertension, palpitations, tachycardia. GI: constipation, diarrhea, dry mouth, nausea, unpleasant taste, vomiting. GU: changes in libido, erectile dysfunction.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Periodically assess body weight and other anthropometric measures (body mass index, body composition) to document whether drug therapy is successful in promoting weight loss.

• Be alert for signs of excessive CNS effects, including hyperactivity, restlessness, tremor, confusion, hallucinations, depression, or other changes in mood and behavior. Report these signs to the physician.

• Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report fast heart rate (tachycardia), or symptoms of other arrhythmias, including palpitations, chest discomfort, shortness of breath, fainting, and fatigue/weakness.

• Assess blood pressure (BP) and compare to normal values (See Appendix F). Report a sustained increase in BP (hypertension).

• Assess dizziness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

Interventions

• Because of the risk of arrhythmias and abnormal BP responses, use caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (BP, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

Patient/Client-Related Instruction

• Make sure the patient has discussed use of this drug with his/her physician. Advise patient about the potential cardiac and CNS risks, and counsel patient about other interventions (diet, exercise) that can help achieve and maintain weight loss.

• Instruct patient and family/caregivers to report other troublesome side effects, including severe or prolonged headache, blurred vision, sleep loss, sexual problems (changes in libido, erectile dysfunction), or GI problems (nausea, vomiting, constipation, diarrhea, unpleasant taste, dry mouth).

Pharmacokinetics

Absorption: Unknown.

Distribution: Unknown.

Metabolism and Excretion: Metabolized by the liver.

Half-life: 19–24 hr.