What baseline evaluations (vital signs, BMI, cardiovascular screening, metabolic panel, thyroid function, pregnancy test, psychiatric and substance‑use screen, and medication review) are required before prescribing Adipex (phentermine) for weight loss?

Pre-Treatment Testing Required Before Prescribing Adipex (Phentermine)

Before prescribing Adipex, you must obtain baseline blood pressure and heart rate measurements, screen for cardiovascular disease and contraindications (including pregnancy status in women of reproductive potential, hyperthyroidism, glaucoma, MAOI use, and psychiatric conditions), and assess BMI to confirm eligibility. 1

Mandatory Baseline Assessments

Cardiovascular Screening

• Measure baseline blood pressure and heart rate at the initial visit, as phentermine causes mild increases in both through sympathetic nervous system activation 2, 1
• Screen for any history of cardiovascular disease, including coronary artery disease, stroke, arrhythmias, congestive heart failure, or uncontrolled hypertension—any of these are absolute contraindications 1, 3
• Even mild uncontrolled hypertension requires caution, though patients with controlled hypertension may be considered with intensive monitoring 1

Body Mass Index Verification

• Confirm BMI ≥27 kg/m² with weight-related comorbidities or BMI ≥30 kg/m² to establish appropriate indication for pharmacotherapy 2

Pregnancy and Reproductive Status

• Assess pregnancy status in all women of reproductive potential, as phentermine is absolutely contraindicated in pregnancy 1
• Provide contraception counseling and document adequate contraceptive measures before initiating therapy 1
• Consider monthly pregnancy testing if prescribing beyond 12 weeks 1

Endocrine Screening

• Exclude hyperthyroidism before starting phentermine, as this is a contraindication due to additive sympathomimetic effects 1

Ophthalmologic History

• Screen for glaucoma, particularly angle-closure glaucoma, which is a contraindication to sympathomimetic agents 1

Psychiatric Assessment

• Evaluate for agitated states, anxiety disorders, or history of substance abuse, as phentermine's stimulant properties may exacerbate these conditions 1
• Screen for current or recent MAOI use (within 14 days), which is an absolute contraindication due to risk of hypertensive crisis 1

Metabolic Panel Considerations

• While not explicitly mandated by guidelines, assess renal function as part of comprehensive metabolic evaluation, particularly if considering combination therapy or in patients with diabetes 2
• Measure serum bicarbonate if considering phentermine-topiramate combination (though this applies to the combination product, not phentermine monotherapy) 2

Common Pitfalls to Avoid

• Do not confuse phentermine monotherapy with the discontinued "fen-phen" combination (phentermine-fenfluramine)—the cardiovascular risks (valvular heart disease, pulmonary hypertension) were attributed to fenfluramine, not phentermine 1
• Do not prescribe to any patient with cardiovascular disease history, even if currently stable—this is an absolute contraindication per gastroenterology guidelines 3
• Do not skip pregnancy screening in women of reproductive age—this is a critical safety measure given absolute contraindication in pregnancy 1

Patient Counseling Requirements

• Inform patients that FDA approval is technically for short-term use (3 months), though many clinicians use it longer off-label for chronic obesity management 1
• Discuss common side effects: dry mouth, insomnia, dizziness, irritability, increased blood pressure, and elevated heart rate 2, 1
• Establish monitoring plan: blood pressure and heart rate at every visit, with discontinuation if <5% weight loss after 12 weeks on maximum dose 1

Alternative Medications for High-Risk Patients

If cardiovascular contraindications exist:

• Consider orlistat (lipase inhibitor with no sympathomimetic effects) 2, 3
• Consider GLP-1 receptor agonists (semaglutide 2.4 mg or liraglutide 3.0 mg) which offer superior efficacy with different safety profiles and cardiovascular benefits 1, 3