What are the potential side effects of Lomaira (phentermine) in adults or adolescents with a body mass index (BMI) of 30 or higher, or a BMI of 27 or higher with at least one weight-related condition?

Side Effects of Lomaira (Phentermine)

Lomaira (phentermine 8 mg) causes common side effects including headache, elevated blood pressure, elevated heart rate, insomnia, dry mouth, constipation, anxiety, and palpitations, with serious adverse effects including dyspnea, angina pectoris, syncope, and severe hypertension. 1

Common Side Effects

The most frequently reported adverse effects of phentermine include:

• Dry mouth - occurs commonly and can be managed with adequate hydration 2
• Insomnia/difficulty sleeping - avoid late evening dosing to minimize this effect 2, 3
• Headache - reported frequently in clinical trials 1
• Elevated blood pressure - requires periodic monitoring throughout treatment 1
• Elevated heart rate - typically increases by 5-10 beats per minute, particularly at 9-12 months 1, 4
• Constipation - common gastrointestinal effect 1
• Anxiety and irritability - due to sympathomimetic stimulation 1, 2
• Palpitations - related to adrenergic effects 1
• Dizziness - reported in clinical practice 2, 5

Serious Adverse Effects

Life-threatening or severe complications that require immediate discontinuation include:

• Dyspnea (shortness of breath) - may indicate cardiovascular compromise 1
• Angina pectoris - chest pain suggesting cardiac ischemia 1
• Syncope - loss of consciousness requiring urgent evaluation 1
• Severe hypertension - can lead to hypertensive crisis 1
• Arrhythmias - particularly in patients with untreated hyperthyroidism 1

Neuropsychiatric Side Effects

Phentermine's stimulant properties can cause:

• Mood changes - reported in 25.8% of patients at 3 months 4
• Fatigue - paradoxically occurs despite stimulant effects 4
• Mental illness exacerbation - in susceptible individuals 6
• Agitated states - contraindication for use 3

Cardiovascular Monitoring Requirements

Blood pressure and heart rate must be monitored at baseline and periodically throughout treatment due to phentermine's sympathomimetic effects that activate the sympathetic nervous system. 1, 2, 5

In pivotal trials, blood pressure generally declined with treatment, but small increases in heart rate occurred, usually at higher doses. 1 Real-world data shows heart rate increases of 5-10 beats per minute specifically at 9 and 12 months of treatment. 4

Special Safety Considerations

Absolute Contraindications

Phentermine is contraindicated in patients with:

• History of cardiovascular disease (coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) 3
• During or within 14 days of MAOI use - risk of hypertensive crisis 1, 3
• Hyperthyroidism - risk of arrhythmias and seizures 1, 3
• Glaucoma - sympathomimetic effects worsen condition 3
• Pregnancy and nursing - teratogenic concerns 3
• History of drug abuse - Schedule IV controlled substance 3
• Agitated states - stimulant properties exacerbate condition 3

Vascular and Metabolic Risks

Case reports suggest phentermine usage might be associated with:

• Hypertension - through vasoconstriction 6
• Vasoconstriction and vasculopathy - in susceptible individuals 6
• Unpredictable health risks - particularly with unmonitored use 6

Common Pitfalls to Avoid

Do not confuse phentermine monotherapy with the discontinued "fen-phen" combination (phentermine-fenfluramine). The serious cardiovascular risks of valvular heart disease and pulmonary hypertension were attributed to fenfluramine, not phentermine. 5 This historical association has created unwarranted concerns about phentermine's cardiovascular safety profile.

Discontinuation Criteria

Discontinue phentermine immediately if:

• Less than 5% weight loss after 12 weeks on maximum dose 1, 2
• Any serious adverse effects occur (dyspnea, angina, syncope, severe hypertension) 1
• Side effects are unacceptable to the patient 7
• Cardiovascular symptoms emerge during treatment 2

Side Effect Management Strategy

For patients experiencing common side effects:

• Insomnia - avoid late evening dosing, take medication approximately 2 hours after breakfast 3
• Dry mouth - increase fluid intake 1
• Constipation - add fiber supplement, ensure adequate hydration 1
• Elevated heart rate/blood pressure - monitor at every visit, consider dose reduction or discontinuation if uncontrolled 2, 5

The 8 mg formulation (Lomaira) can be dosed up to 3 times daily approximately 30 minutes before meals, with scored tablets allowing doses as low as 4 mg for better tolerability. 1, 2