Constipation on Opioid Therapy: Prescribing a Laxative Regimen

Patient P-104 is a 70-year-old woman with advanced breast cancer and bone metastases. She has been taking modified-release morphine 30 mg twice daily for three weeks for cancer-related pain. She weighs 60 kg. She presents with a four-day history of worsening constipation, abdominal pain, and reduced appetite. She has opened her bowels only once in the last four days, passing small hard stools. She has no nausea or vomiting. On examination, her abdomen is distended, mildly tender in the left lower quadrant, with normal bowel sounds. There is no peritonism. Her oral intake is reduced, but she is drinking fluids. She has no known allergies. Her regular medicines are modified-release morphine 30 mg twice daily, paracetamol 1 g four times daily as needed, and dexamethasone 4 mg once daily for the past week. Her temperature is 36.8°C, heart rate 88 bpm, blood pressure 128/76 mmHg. Investigations: serum creatinine 0.8 mg/dL (70 µmol/L), eGFR 75 mL/min/1.73m². Urea and electrolytes are otherwise normal. She is not pregnant. She requires an appropriate laxative regimen for her constipation. Prescribe the laxatives as an inpatient prescription.