Phentermine

Selected single-agent products are labeled for a few weeks as an adjunct in exogenous obesity with initial BMI at least 30 kg/m², or at least 27 kg/m² with risk factors such as controlled hypertension, diabetes or hyperlipidemia. Assess benefit against inherent cardiovascular and stimulant risks. Controlled hypertension as a BMI-associated risk factor does not remove BP precautions.

The reviewed labels recommend adult dosing and do not recommend use at age 16 or younger; pediatric effectiveness is not established, and chronic pediatric obesity is not a justification for short-term prescribing. Longer-term single-agent prescribing is outside the labeled course reviewed here. Phentermine/topiramate ER has separate approval, dosing, pregnancy, monitoring and discontinuation requirements; do not derive that regimen from phentermine monotherapy.

The selected Aurolife and 15/30 or 37.5 mg capsule labels limit dosing to 15 mg/day at eGFR 15–29 mL/min/1.73 m² and advise avoiding use below 15 or with dialysis-dependent ESRD. A 37.5 mg tablet or capsule does not itself supply the 15 mg dose; use the actual prescribed lower-strength product. Current Lomaira text provides renal caution without a numerical algorithm; do not automatically transfer another product’s adjustment to an 8 mg three-times-daily prescription.

Avoid late-evening doses because insomnia can occur. Treat for the labeled few-week course and reassess response, BP, tolerability and need; do not infer a universal long-term renewal schedule. If anorectic tolerance develops, discontinue rather than exceed the recommended dose. With prolonged high-dose use, abrupt cessation can cause severe fatigue and depressed mood; clinicians should assess misuse and the stopping plan.

Selected labels give no numerical hepatic-adjustment regimen. In older patients start cautiously at the lower end, considering renal, hepatic/cardiac disease and other medicines; renal monitoring can guide safe selection. Do not invent a dose solely from age or a conversion from another obesity medicine.

History of cardiovascular disease, including coronary disease, stroke, arrhythmias, heart failure or uncontrolled hypertension; MAOI use or within 14 days afterward; hyperthyroidism; glaucoma; agitated states; history of drug abuse; pregnancy; nursing; or sympathomimetic hypersensitivity/idiosyncrasy. These are contraindications, not merely monitoring suggestions.

The selected single-agent phentermine labels have no boxed warning. Schedule IV status, contraindications, pulmonary/cardiovascular risks and misuse precautions still require careful assessment.

Reported effects include dry mouth, unpleasant taste, constipation or diarrhea; insomnia, restlessness, dizziness, tremor, headache and mood changes; palpitations, tachycardia, increased BP and ischemic events; urticaria; and sexual-function changes. Psychosis, dependence and serious cardiopulmonary events are possible. The selected labels do not establish one reliable adverse-event frequency.

Phentermine is contraindicated during MAOI treatment and within 14 days following it because hypertensive crisis can occur. The monotherapy label does not establish combination safety with other weight-loss products or SSRIs such as fluoxetine or sertraline and recommends against coadministration. Phentermine/topiramate ER requires its own label rather than independently assembled doses.

Alcohol can provoke adverse reactions. Insulin or oral glucose-lowering requirements may change; monitor glucose and adjust with the treating clinician. Phentermine may reduce the BP-lowering effect of adrenergic neuron blockers. Reconcile other stimulants and OTC products clinically because BP, pulse or insomnia may worsen.

Kidney impairment raises phentermine exposure. When changing products, verify hydrochloride versus base units and actual formulation/meal directions, not just the number on a capsule. The label’s single-dose topiramate interaction study found higher phentermine exposure; it is not a dosing instruction for combination obesity treatment.

Pregnancy is contraindicated: intended weight loss offers no benefit during pregnancy and may harm the fetus. The reviewed labels also contraindicate nursing; discuss stopping the drug versus nursing with the treating team rather than continue both by assumption. Human milk excretion of phentermine is unknown in these labels, but other amphetamines appear in milk; animal reproduction studies were not conducted.

Use at age 16 or younger is not recommended, and pediatric safety/effectiveness are not established. These restrictions do not create an automatic weight-based teenage dose. Older patients require cautious dose selection and consideration of renal function, cardiovascular disease and polypharmacy.

Selected modern tablet/capsule labels provide the severe-renal 15 mg/day ceiling and avoidance below eGFR 15 or with dialysis. Lomaira’s current label gives caution only; obtain a product-specific prescription review. No fixed hepatic adjustment is supplied. Cardiovascular disease is contraindicated; even mild hypertension needs caution and monitoring.

Phentermine has pharmacologic activity similar to amphetamine, with CNS stimulation and BP elevation. The primary obesity-treatment mechanism is not fully established; appetite effects, other CNS actions and metabolic effects may contribute. Tolerance/tachyphylaxis can develop.

Selected modern labels report peak concentrations after 3–4.4 hours and urinary recovery of 62–85% under uncontrolled urine-pH conditions. Renal impairment increases exposure; this supports cautious selection and the selected numerical renal limits. The single-dose topiramate study increased phentermine peak and AUC exposure by 13% and 42%, respectively; this does not establish monotherapy-to-combination equivalence.

Assess BMI/indication, contraindications, BP/pulse, renal function when relevant and all medicines before prescribing. Follow weight response, nutrition/activity plan, BP/pulse, sleep, mood and tolerance; review glucose requirements in diabetes. Investigate cardiopulmonary warning symptoms promptly. The label supplies no universal visit frequency or long-term response threshold.

Take the exact prescribed product and timing; avoid late-evening dosing, alcohol and unreviewed weight-loss or serotonergic products. Do not increase the dose for fading benefit. Store securely, never share and use caution driving until effects are known. Report pregnancy, major mood changes, new dyspnea/chest pain, fainting or edema promptly.

Overdose may cause severe agitation, tremor, hallucinations, hypertension or hypotension, arrhythmia, collapse, seizures or coma. Seek urgent medical or Poison Control help; do not attempt urine acidification, gastric decontamination or sedative treatment at home. Management is specialist supportive care; the label has insufficient dialysis experience for a reliable recommendation.

Product

Aurolife phentermine HCl 37.5 mg tablet

Route/status

Oral; prescription Schedule IV

Appearance

White to off-white with blue specks; U40 / break line

Example package

30 tablets · NDC 13107-061-30

Reviewed: 37.5 mg hydrochloride tablets/capsules (equivalent to 30 mg base); selected 15/30 mg hydrochloride capsules; Lomaira 8 mg hydrochloride scored tablets. The current Lomaira source is a repackager label with underlying KVK product information: verify the actually dispensed NDC rather than assume the manufacturer’s bottle number. Other brands, orally disintegrating formulations and phentermine/topiramate ER are outside this dosing scope.

Aurolife tablets and Lomaira: 20–25°C (68–77°F) in a tight container with required child-resistant closure. Selected capsule labels: 20–25°C, excursions to 15–30°C, tight light-resistant container with required child-resistant closure. Secure against theft, misuse and accidental access. No universal opened-container discard interval is supplied.