Morphine is a powerful opioid medication prescribed for managing severe pain. It reduces pain by acting on the central nervous system. However, morphine can cause various side effects, including urinary retention. This condition, where the bladder cannot empty completely, requires attention for individuals receiving morphine therapy.
Understanding Morphine’s Effect on the Urinary System
Morphine causes urinary retention by interfering with the neural control of bladder function. It acts on mu-opioid receptors in the central nervous system and peripheral areas like the bladder. This disrupts the normal signals that regulate urination.
Morphine decreases the contractility of the detrusor muscle, the main bladder muscle responsible for expelling urine. This causes the muscle to relax, making it difficult for the bladder to empty. It also increases the tone of the external urethral sphincter, which controls urine flow, hindering release. Opioids diminish the sensation of bladder fullness, so a person might not feel the urge to urinate even when the bladder is distended. These actions lead to urine accumulating in the bladder, resulting in retention.
Identifying Urinary Retention
Recognizing the signs of urinary retention is important. A primary symptom is difficulty or inability to urinate, even with a strong urge. This often accompanies a feeling of fullness or pressure in the lower abdomen, ranging from discomfort to pain. The bladder may feel firm and distended above the pubic bone.
Sometimes, urinary retention can manifest as frequent small urinations, known as overflow incontinence. This occurs when the bladder becomes so overfilled that small amounts of urine leak out involuntarily. Patients might also describe a persistent sensation that their bladder has not emptied completely after attempting to urinate. These symptoms should prompt immediate medical evaluation, as untreated retention can lead to complications.
Addressing Urinary Retention
Prompt medical attention is necessary if urinary retention is suspected in someone taking morphine. A healthcare provider can assess the situation, often using a bladder scan to measure the amount of urine remaining in the bladder. If significant retention is confirmed, catheterization, which involves inserting a thin tube into the bladder to drain the urine, may be performed to relieve pressure and prevent further complications.
Management strategies also involve adjusting the morphine therapy under medical supervision. This could mean reducing the dosage of morphine, or in some cases, switching to a different type of pain medication that has a lower likelihood of causing urinary retention. Certain medications, such as peripheral opioid antagonists like methylnaltrexone or partial opioid antagonists like nalbuphine, can also be used to counteract the opioid’s effects on the bladder without significantly reversing its pain-relieving properties. Non-pharmacological approaches, such as applying a warm compress to the lower abdomen or attempting to urinate in a relaxed environment, might offer minor relief but are not a substitute for professional medical care. Healthcare providers often monitor patients receiving opioids for this side effect and may implement strategies like encouraging regular voiding to help prevent its occurrence.