Medication Reconciliation Identifying Duplicate Opioid Therapy and Clinically Significant Drug Interactions

Patient Background

Mr. A.B. is a 68-year-old male who presented to his primary care clinic for a comprehensive medication review following a recent hospitalization for chronic pain management. His medical history included chronic osteoarthritis, lumbar degenerative disc disease, type 2 diabetes mellitus, hypertension, hyperlipidemia, epilepsy, gastroesophageal reflux disease, and chronic lower extremity edema. He had been under the care of multiple healthcare providers, including a primary care physician, orthopedic surgeon, neurologist, and pain management specialist.

His current medication regimen included:

• Morphine extended-release 15 mg twice daily
• Oxycodone 5 mg every 4 hours as needed
• Hydrocodone/acetaminophen 5/325 mg every 6 hours as needed
• Tramadol 50 mg every 6 hours as needed
• Acetaminophen 1,000 mg three times daily
• Cimetidine 400 mg twice daily
• Sertraline 100 mg daily
• Phenytoin 300 mg daily
• Lisinopril 20 mg daily
• Metformin 1,000 mg twice daily
• Atorvastatin 40 mg nightly
• Furosemide 40 mg daily
• Potassium chloride extended-release 20 mEq daily
• Aspirin 81 mg daily
• Senna 17.2 mg nightly
• Clinical Presentation:

Clinical Presentation

During the consultation, Mr. A.B. reported persistent daytime drowsiness, intermittent dizziness, constipation, and occasional difficulty concentrating. Although his pain was reasonably controlled, he admitted that he was uncertain which “as-needed” opioid he should use, often alternating between oxycodone, hydrocodone/acetaminophen, and tramadol depending on which medication he found first.

Medication reconciliation revealed that several opioid prescriptions had accumulated over time following hospital admissions, outpatient procedures, and consultations with different prescribers. None of the previous opioid prescriptions had been formally discontinued despite changes in his pain management plan.

Clinical Issue Identified

A comprehensive medication review identified multiple drug therapy problems, the most significant being unnecessary duplicate opioid therapy. The concurrent availability of oxycodone, hydrocodone/acetaminophen, and tramadol as needed, in addition to scheduled extended-release morphine, substantially increased the patient’s risk of:

• Excessive sedation
• Respiratory depression
• Falls
• Constipation
• Medication errors
• Opioid overdose

Furthermore, the patient was already receiving scheduled acetaminophen (3 g/day), making the hydrocodone/acetaminophen combination unnecessary while increasing cumulative acetaminophen exposure.

An additional safety concern involved tramadol, which lowers the seizure threshold. Given the patient’s history of epilepsy and chronic treatment with phenytoin, tramadol represented an avoidable risk for seizure precipitation.

Medication review also identified a clinically significant drug interaction between cimetidine and phenytoin. Cimetidine is a potent inhibitor of several cytochrome P450 enzymes and can reduce phenytoin metabolism, increasing serum phenytoin concentrations and predisposing the patient to toxicity.

Pharmacist Intervention and Clinical Management

Optimization of Opioid Therapy

• Discontinue hydrocodone/acetaminophen to eliminate duplicate opioid therapy and reduce unnecessary acetaminophen exposure.
• Discontinue tramadol because of its limited additional analgesic benefit and increased seizure risk.
• Continue a simplified analgesic regimen consisting of scheduled morphine extended-release with oxycodone as the sole breakthrough opioid, if clinically indicated.

Review of Drug Interactions

• Identify the clinically significant interaction between cimetidine and phenytoin.
• Recommend replacing cimetidine with an alternative acid-suppressive agent that has minimal CYP450 inhibition (e.g., famotidine), if appropriate.

Monitoring and Follow-Up

• Obtain a serum phenytoin concentration to assess for potential toxicity.
• Monitor for clinical signs of phenytoin toxicity, including:
  • Nystagmus
  • Ataxia
  • Slurred speech
  • Confusion
  • Diplopia
• Reassess pain control, opioid requirements, bowel function, and sedation following medication simplification.

Patient Education

• Educate the patient regarding the appropriate use of breakthrough opioid therapy.
• Reinforce the importance of maintaining an accurate medication list and informing all healthcare providers of current medications.
• Counsel on recognizing symptoms of opioid toxicity and phenytoin toxicity and when to seek immediate medical attention.

Interprofessional Communication

• Communicate recommendations to the primary care physician and pain management team.
• Update the patient’s medication list to eliminate inactive prescriptions and reduce future prescribing errors.

Clinical Rationale and Ramifications

This case highlights the importance of comprehensive medication reconciliation, particularly in patients receiving care from multiple healthcare providers. Failure to discontinue obsolete medications resulted in duplicate opioid therapy, increasing the patient’s risk of excessive sedation, falls, respiratory depression, and medication errors without providing additional analgesic benefit.

The case also demonstrates how medication review can identify clinically significant drug interactions unrelated to the presenting complaint. The concomitant use of cimetidine and phenytoin placed the patient at risk of elevated phenytoin concentrations and neurological toxicity through inhibition of hepatic metabolism.

By simplifying the analgesic regimen, discontinuing unnecessary medications, and addressing important pharmacokinetic interactions, the pharmacist reduced medication burden, improved patient safety, and minimized the risk of preventable adverse drug events. This case reinforces the critical role of routine medication reconciliation and deprescribing in optimizing pharmacotherapy, particularly in older adults with multimorbidity and polypharmacy.