A Step-by-Step Guide to Prescribing Weight Loss Medications After Bariatric Surgery

There is growing interest within the medical community in using weight loss medications after bariatric surgery. Many patients—25% to 35%, according to data published in Surgery for Obesity and Related Diseases—regain weight or experience inadequate weight loss postoperatively.

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Fatima Cody Stanford, MD, MPH, MPA, an obesity medicine physician for adults, adolescents and children at the Massachusetts General Hospital Weight Center, and colleagues have published evidence that weight loss medications are effective after bariatric surgery in adults as young as 21 years of age. In additional research published in Surgery for Obesity and Related Diseases, Dr. Stanford provides critical, step-by-step guidance for introducing weight loss medications after bariatric surgery.

Preliminary Considerations

Patients meet criteria for weight loss medication if they have a body mass index ≥30, or ≥27 with a significant obesity-related disease such as type 2 diabetes, obstructive sleep apnea or hypertension. An exception is that women should not use weight loss medication before conception or during pregnancy.

Before recommending weight loss medication, take a thorough medical history and order an upper gastrointestinal study. Problems such as staple line breakdown and postoperative leaks require revision surgery.

Shared Decision-making

Counsel patients that obesity is a chronic disease and weight loss medication will need to be continued even after the desired amount of weight loss has been achieved. Also, reinforce the importance of a good diet, physical activity and sufficient sleep in conjunction with medications.

Initiating Topiramate

Consider prescribing topiramate as the initial weight loss drug after bariatric surgery (off-label for this purpose). Dr. Stanford and her colleagues recommend starting with 25 mg at bedtime as soon as weight loss reaches a plateau or when weight regain begins despite optimal lifestyle. Evening dosing reduces the impact of cognitive changes, and it can quell evening food cravings and improve sleep.

Topiramate Side Effects and Follow-up

Notify patients of the possibility of cognitive changes (e.g., word-finding difficulty) and paresthesias. Patients taking topiramate regularly should have their electrolytes monitored to check for metabolic acidosis.

Follow-up should occur at least monthly after initiation of a weight loss agent or with dose adjustments. Titrate topiramate up by 25 mg at each monthly visit, but only if necessary (e.g., if weight loss has halted). Dr. Stanford's maximum evening dose is generally 100 mg, or 150 mg for some patients. Individualized dosing is important. If side effects occur, reduce to the previous dose and maintain therapy there.

If the patient has side effects but good weight loss response (5% to 10% total weight loss), consider switching to extended-release topiramate. One might consider patients in this population successful if they achieve weight maintenance or no further weight gain; however, many insurers insist on the 5% to 10% target.

Alternative Agents

Nephrolithiasis can occur with topiramate. If the patient has a history of that condition, recommend an alternative agent or have the patient monitored by an obesity medicine physician.

For patients currently using psychotropic medication, consider adding metformin to topiramate. For weight loss, Dr. Stanford titrates most patients on metformin to 1000 mg by mouth twice daily. Gastrointestinal side effects can often be mitigated by extended-release metformin.

If weight loss on topiramate is <5%, or if side effects are intolerable, consider an alternative agent such as zonisamide, whose mechanism of action is similar to that of topiramate. For weight loss, Dr. Stanford and her colleagues generally start zonisamide at 100 mg in the evening and titrate up monthly by 100 mg to a maximum of 400 mg.

Discontinuing Topiramate and Zonisamide

Topiramate and zonisamide are antiepileptics, and rapid cessation may induce seizures. Tapering from one dose to another dose should occur every three days (e.g., a patient on 100 mg of topiramate would take 75 mg in the evening for three nights, 50 mg for three nights, 25 mg for three nights, then stop.)

Using Multiple Agents

A second agent might be added when the patient reaches weight stability or once a rebound occurs. It is important to combine agents from different classes (e.g., topiramate/phentermine, topiramate/liraglutide, zonisamide/bupropion or bupropion/naltrexone).

To topiramate or zonisamide, Dr. Stanford and her colleagues typically add phentermine, 15 mg extended release in the morning with titration to 30 mg. They have the patient obtain blood pressure and pulse readings on Monday mornings, Wednesday afternoons, and Friday evenings at the start of the medication and whenever the dose is adjusted. Blood pressure >140/90 mm Hg or pulse >96 beats/min suggest phentermine may be unsuitable.

Patients should never be blamed for weight gain or inadequate weight loss after bariatric surgery. Genetics and postoperative changes in gut hormones are apt to explain the suboptimal response.

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