Can an adult patient with a history of substance abuse or addiction and anxiety disorders take phentermine with Suboxone (buprenorphine and naloxone) and 2mg of Ativan (lorazepam) spaced out?

Phentermine with Suboxone and Ativan: Strong Contraindication

This combination should NOT be used due to multiple serious safety concerns, particularly the absolute contraindication between naltrexone-containing medications and opioids (Suboxone contains buprenorphine, an opioid), and the high-risk interaction between benzodiazepines and opioids that carries an FDA black box warning.

Critical Drug Interaction: Naltrexone and Opioids

While the question asks about phentermine specifically, it's crucial to note that naltrexone-bupropion (a weight loss medication containing naltrexone) should not be used concomitantly with opiate medications 1. Although phentermine doesn't contain naltrexone, this highlights the complexity of managing weight loss medications in patients on opioid therapy. Phentermine itself has no direct pharmacologic contraindication with buprenorphine, but the overall combination presents significant risks.

FDA Black Box Warning: Benzodiazepines and Opioids

The FDA issued black box warnings on all benzodiazepines and opioid analgesics regarding serious risks associated with their concomitant use 2. This applies directly to the Ativan (lorazepam) and Suboxone (buprenorphine/naloxone) combination:

• Increased risk of respiratory depression that exceeds either agent alone 3
• Enhanced sedation requiring dose reduction of both medications by 25-50% if combination is unavoidable 3
• Risk of overdose and death from combined CNS depression

Special Considerations for Substance Use Disorder History

Patients with substance use disorders should not use benzodiazepines for any indication, as the addiction "switch" once activated never turns off 2. This is particularly relevant given:

• The patient is on Suboxone, indicating opioid use disorder treatment 4
• Benzodiazepines have significant addiction potential, especially lorazepam and other short-acting agents 5
• Benzodiazepines should be avoided in patients with substance abuse history due to dependence potential 6, 3

Phentermine-Specific Concerns

While phentermine can be used in patients with anxiety disorders, caution should be exercised in individuals with anxiety disorders and depression, and those taking antidepressants 1. Additional concerns include:

• Common adverse effects include anxiety, insomnia, dizziness, and irritability 1, which may worsen in patients already requiring anxiolytic therapy
• Blood pressure and heart rate should be monitored periodically while taking phentermine 1
• Phentermine is a Schedule IV controlled substance with concerns for abuse and dependence 1

Potential Drug-Drug Interactions

Long-term phentermine use is associated with potential drug-drug interactions that may result in adverse drug reactions 7. When combined with multiple CNS-active agents:

• Monitor closely for increased sedation or respiratory depression 6
• Consider using lower doses of all medications when used in combination 6
• Monitor for orthostatic hypotension, sedation, and vertigo 6

Clinical Recommendation Algorithm

If weight management is needed in this patient:

1. Discontinue or avoid initiating this three-drug combination due to safety concerns
2. Address benzodiazepine use first: Taper Ativan gradually and transition to non-benzodiazepine alternatives for anxiety management, as benzodiazepines are contraindicated in patients with substance use disorders 2
3. Consider alternative weight loss medications that don't compound CNS depression risks:
   • GLP-1 receptor agonists (semaglutide 2.4 mg or liraglutide 3.0 mg) are preferred first-line agents with superior efficacy 1
   • These agents lack the CNS stimulant effects and addiction potential of phentermine 1
4. If phentermine is deemed essential after benzodiazepine discontinuation:
   • Ensure stable psychiatric management without benzodiazepines
   • Start at lowest effective dose (7.5 mg daily) 1
   • Monitor blood pressure, heart rate, and psychiatric symptoms closely 1
   • Coordinate care with the prescriber managing Suboxone therapy 4

Common Pitfalls to Avoid

• Never combine benzodiazepines with opioids unless absolutely necessary for acute, severe conditions with intensive monitoring 2
• Do not prescribe phentermine as stand-alone treatment; it must be combined with lifestyle interventions 1
• Avoid assuming "spacing out" doses eliminates interaction risks—pharmacodynamic interactions persist regardless of timing when drugs have overlapping half-lives
• Do not use this combination in patients with severe respiratory compromise 6, 3