In this case scenario, we describe how and why dicyclomine and BPH can be a bad combination. Jim is a 68-year-old retired teacher who visits his primary care provider complaining of intermittent lower abdominal cramping that has been occurring for several months. The discomfort is worse after meals and tends to improve after bowel movements. He denies weight loss, fever, or blood in the stool. He has a known history of IBS, but it has never been this bad.
His past medical history includes hypertension, benign prostatic hyperplasia (BPH), hyperlipidemia, and gastroesophageal reflux disease. His current medications include lisinopril 20 mg daily, atorvastatin 20 mg nightly, tamsulosin 0.4 mg daily, and omeprazole 20 mg daily. Although he has mild urinary hesitancy from his BPH, his symptoms have been well controlled on tamsulosin.
To improve his abdominal cramping, his provider prescribes dicyclomine (Bentyl) 20 mg four times daily before meals and at bedtime.
Initially, Jim is happy with the results. Within several days, his abdominal cramping improves significantly, and he is able to enjoy meals without the painful spasms that had been affecting his quality of life. About two weeks later, however, Jim notices increasing difficulty urinating. His urinary stream becomes progressively weaker, and he feels like he cannot completely empty his bladder. He begins waking several times each night with an intense urge to urinate but is only able to pass a small amount of urine.
One evening, he develops severe lower abdominal pain and realizes he has been unable to urinate for nearly 12 hours. His wife brings him to the emergency department. On examination, he has a markedly distended and tender bladder. A bladder scan reveals over 900 mL of retained urine. A urinary catheter is inserted, immediately draining a large volume of urine and providing rapid relief of his discomfort.
As the emergency physician reviews his medication list, the recently started dicyclomine stands out. Because dicyclomine is a potent anticholinergic medication, it relaxes smooth muscle throughout the body, including the detrusor muscle of the bladder. In a patient with underlying benign prostatic hyperplasia, reducing bladder contractility can tip the balance from mild urinary hesitancy to complete urinary retention. Dicyclomine is discontinued, and Jim continues his tamsulosin. After several days, the catheter is successfully removed, and his urinary function gradually returns to his previous baseline.
Practice Pearl
This is an excellent example of why healthcare professionals should always consider underlying disease states before initiating medications with anticholinergic properties. Dicyclomine and BPH do not mix well. Patients with BPH already have mechanical obstruction to urine flow due to prostate enlargement. Adding an anticholinergic medication like dicyclomine or hyoscyamine decreases bladder muscle contraction, making it much more difficult to overcome that obstruction.
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