Rhabdomyolysis associated with phentermine

Area of Science:

• Pharmacology
• Nephrology
• Toxicology

Background:

• Phentermine is a sympathomimetic amine used for short-term weight management.
• Adverse drug events require thorough investigation, especially when associated with high-risk patient populations or unusual dosages.
• Rhabdomyolysis is a condition involving the breakdown of skeletal muscle tissue.

Observation:

• A 32-year-old male presented with severe muscle pain and elevated creatine kinase levels after taking double the recommended dose of phentermine for one week.
• The patient also engaged in strenuous exercise, which may have contributed to the condition.
• Initial laboratory results revealed significantly elevated troponin I, creatine kinase (CK), CK-MB, and serum creatinine.

Findings:

• The patient was diagnosed with rhabdomyolysis affecting multiple muscle groups and secondary acute kidney injury.
• Phentermine was identified as the probable cause of rhabdomyolysis using the Naranjo adverse-event probability scale.
• The patient's renal function improved with intravenous hydration and urinary alkalinization, avoiding the need for renal replacement therapy.

Implications:

• This case underscores the potential dangers of exceeding prescribed phentermine dosages.
• Healthcare providers should carefully monitor patients on phentermine, especially those with risk factors for muscle injury.
• Further research into the dose-dependent toxicity of phentermine is warranted to inform clinical practice and patient safety guidelines.