Medicines in Childhood Obesity

Childhood obesity is managed first with family-based changes in diet, activity, sleep and screen time. Medicines are an adjunct for selected adolescents, for complications such as type 2 diabetes and hypertension, and for rare genetic obesity. Dosing of other medicines in an obese child also needs adjustment.

Definition. Body mass index at or over the 95th centile (or over 2 z-scores in many regions) for age and sex, with severe obesity at 120% of the 95th centile or over.

Medicine-induced weight gain. Review olanzapine, risperidone, valproate, prolonged corticosteroids, insulin overdosing, and certain antidepressants before adding weight-loss treatment.

• Liraglutide: for adolescents 12 years and over with obesity. Start 0.6 mg subcutaneously once daily and increase by 0.6 mg each week to 3 mg daily, if tolerated. Review after 12 weeks at the maintenance dose and consider stopping if body mass index has fallen by under 4%.
• Semaglutide: for adolescents 12 years and over. Start 0.25 mg subcutaneously once weekly, increase every 4 weeks to 0.5 mg, 1 mg, 1.7 mg, and then 2.4 mg weekly as tolerated.
• Orlistat: 120 mg orally with each main meal containing fat (maximum 3 doses daily), 12 years and over, with a multivitamin; limited by gastrointestinal effects.
• Metformin: for insulin resistance or type 2 diabetes, 500 mg once daily with a meal, increased weekly to 1 g twice daily (maximum 2 g/day), 10 years and over. Weight benefit is small.
• Genetic obesity (for example POMC deficiency, Bardet-Biedl syndrome): setmelanotide under specialist direction.
• Complications: hypertension is treated with an ACE inhibitor such as enalapril 0.08 mg/kg/day, starting low, and type 2 diabetes with metformin, adding insulin if ketosis is present; sleep apnoea needs ventilatory support rather than drugs.

Dosing other medicines. Use ideal body weight or adjusted weight (ideal plus 0.4 times the excess) for water-soluble drugs such as gentamicin and vancomycin, actual weight capped at the adult dose for most others, and ideal weight for paracetamol. Never exceed the adult maximum.

Contraindications. Glucagon-like peptide 1 agonists: pregnancy, personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2, and history of pancreatitis. Pregnancy test and effective contraception are needed.

Adverse effects. Nausea, vomiting, diarrhoea, gallstones, pancreatitis and low mood. Fatty liver (raised ALT) needs weight loss and screening.

Special groups. Adolescents with eating disorder history need specialist review. In East Africa, these agents are often unavailable and expensive, and the priority is nutrition counselling, physical activity and treatment of comorbidity, while undernutrition may coexist in the same family.

Monitoring. Body mass index centile every 3 months, blood pressure, fasting glucose or HbA1c, lipids and liver enzymes yearly, and mood and eating behaviour at each visit.

Referral and escalation. Refer severe obesity, suspected genetic or endocrine cause, obstructive sleep apnoea, type 2 diabetes, and any plan for pharmacotherapy to a specialist team.

Stopping. Stop treatment if there is less than 4% body mass index reduction after 12 weeks at maintenance dose, or at intolerance, pregnancy or pancreatitis. Weight is often regained after stopping, so continue lifestyle support.