Is it safe to use phentermine (anorexiant/stimulant) for weight loss while taking Rinvoq (upadacitinib)?

Safety of Phentermine for Weight Loss in Patients Taking Rinvoq (Upadacitinib)

Phentermine should be used with caution in patients taking Rinvoq (upadacitinib) due to potential cardiovascular effects and lack of specific drug interaction studies between these medications.

Phentermine Overview

• Phentermine is an adrenergic agonist that promotes weight loss by activating the sympathetic nervous system, decreasing food intake and increasing resting energy expenditure 1
• It is FDA-approved only for short-term use (3 months), though many providers prescribe it for longer durations as off-label therapy 1
• The recommended dosage is 15-37.5 mg orally once daily in the morning, with dosage individualized to achieve adequate response with the lowest effective dose 1
• Low-dose phentermine (8 mg) can be prescribed up to 3 times per day 1

Cardiovascular Considerations

• Phentermine can cause mild increases in heart rate and blood pressure, which requires careful monitoring 1, 2, 3
• Patients taking Rinvoq may already have underlying inflammatory conditions that could affect cardiovascular health, making additional cardiovascular effects potentially concerning 2
• Long-term observational studies of phentermine have not identified increased risk of cardiovascular events or significant elevations in blood pressure in general populations 4, 3

Potential Drug Interaction Concerns

• There are no specific studies evaluating interactions between phentermine and Rinvoq (upadacitinib)
• Phentermine should not be used with monoamine oxidase inhibitors or other sympathomimetic amines due to potential serious interactions 1
• Patients with active or unstable coronary disease or uncontrolled hypertension are not ideal candidates for phentermine 1

Monitoring Recommendations

• If phentermine is prescribed to a patient on Rinvoq:
  • Monitor blood pressure and heart rate periodically 2
  • Discontinue phentermine if 5% weight loss is not achieved after 12 weeks on maximum dose 2, 5
  • Watch for common side effects including dry mouth, difficulty sleeping, dizziness, and irritability 1
  • Start with the lowest effective dose and titrate carefully 1

Alternative Weight Loss Medications

• Orlistat may be a safer alternative for patients with cardiovascular concerns as it works by inhibiting gastrointestinal lipases rather than affecting the sympathetic nervous system 1
• Orlistat blocks absorption of about 30% of ingested fat and is available as prescription (Xenical 120mg) or over-the-counter (Alli 60mg) 1
• Other FDA-approved weight management medications could be considered based on the patient's specific health profile 2

Clinical Decision-Making Algorithm

1. Assess cardiovascular risk factors in the patient taking Rinvoq
2. If patient has uncontrolled hypertension, active coronary disease, or significant cardiovascular risk factors:
   • Avoid phentermine and consider orlistat or other weight loss options 1, 2
3. If patient has stable cardiovascular status:
   • Consider starting with lowest effective dose of phentermine (15mg or lower) 1
   • Monitor blood pressure and heart rate at baseline and periodically 2
   • Discontinue if cardiovascular parameters worsen or if inadequate weight loss after 12 weeks 2, 5
4. For all patients, emphasize lifestyle modifications including calorie-restricted diet and increased physical activity 1, 2