Is phentermine (generic name for Adipex) contraindicated in patients with a history of opioid use disorder who are being treated with suboxone (buprenorphine and naloxone)?

Phentermine is NOT contraindicated with Suboxone

There is no documented contraindication between phentermine and buprenorphine/naloxone (Suboxone) in current FDA labeling or clinical guidelines. These medications work through entirely different mechanisms and do not have clinically significant pharmacologic interactions.

Mechanism and Safety Profile

• Phentermine is a sympathomimetic amine that acts as an appetite suppressant through norepinephrine release, while buprenorphine is a partial mu-opioid receptor agonist used for opioid use disorder treatment 1

• The CDC guidelines for opioid prescribing and medication-assisted treatment do not list phentermine as a contraindicated or high-risk combination with buprenorphine 1

• The primary drug interaction concerns with Suboxone involve central nervous system depressants (particularly benzodiazepines), not stimulant medications like phentermine 1

Clinical Considerations for Safe Co-Prescribing

• Monitor cardiovascular parameters (blood pressure, heart rate) when prescribing phentermine to any patient, as it can cause tachycardia and hypertension regardless of concurrent medications 2

• Ensure the patient's opioid use disorder treatment is stable on Suboxone before adding phentermine for weight management 1

• Review the state prescription drug monitoring program (PDMP) data to identify any other controlled substances that might create dangerous combinations 1

• Screen for and optimize treatment of co-occurring mental health conditions (depression, anxiety) before initiating phentermine, as these conditions are common in patients with opioid use disorder and can affect treatment outcomes 1, 2

Common Pitfalls to Avoid

• Do not confuse the contraindication of concurrent benzodiazepines and opioids with other medication classes - the fatal respiratory depression risk is specific to combining opioids with other CNS depressants, not stimulants 1

• Avoid prescribing phentermine to patients with uncontrolled hypertension, cardiovascular disease, or hyperthyroidism, as these are standard contraindications for phentermine itself 2

• Do not discontinue effective medication-assisted treatment with Suboxone due to unfounded concerns about drug interactions - buprenorphine maintenance is evidence-based treatment that reduces mortality and illicit opioid use 1, 3

• Ensure patients understand that if they discontinue Suboxone treatment, they have increased risk of opioid overdose due to decreased tolerance 4, 2