Yes, muscle relaxers can cause urinary incontinence, and they do so through several different mechanisms depending on the type of drug. Some relax the muscles that help you hold urine in, while others cause sedation that dulls your awareness of a full bladder. The risk is highest in older adults, women, and people with pre-existing bladder conditions.
How Muscle Relaxers Affect Bladder Control
Your bladder relies on a coordinated system of muscles to store and release urine. A ring of muscle around the urethra (the tube that carries urine out) stays contracted to keep urine in, while the bladder wall muscle stays relaxed during filling. Muscle relaxers can disrupt this balance in two main ways.
The first is direct relaxation of the urethra. Drugs that loosen skeletal muscles throughout the body don’t spare the urethral sphincter. When that ring of muscle can’t squeeze tightly enough, urine leaks out during physical stress like coughing, sneezing, or standing up. This is called stress incontinence, and it’s one of the most commonly reported bladder side effects of these medications.
The second mechanism is sedation. Many muscle relaxers cause drowsiness, which can reduce your awareness of needing to urinate or your motivation to get to the bathroom in time. Harvard Health Publishing lists this combination of urethral relaxation and sedation as the primary reason muscle relaxants and sedatives lead to frequent urination, stress incontinence, and decreased concern about using the toilet.
Which Muscle Relaxers Are Most Linked to Incontinence
Not all muscle relaxers carry the same level of risk. The medications most clearly associated with urinary incontinence fall into a few categories.
Benzodiazepines like diazepam (Valium), chlordiazepoxide (Librium), and lorazepam (Ativan) are frequently prescribed for muscle spasms and carry a well-documented link to bladder problems. A study of frail older adults living in the community found that benzodiazepine users had a 45% increased risk of urinary incontinence compared to non-users. Long-acting benzodiazepines posed the greatest risk, with a 75% increase, because they stay active in the body longer and produce more sustained sedation and muscle relaxation.
Baclofen, commonly prescribed for spasticity in conditions like multiple sclerosis and spinal cord injury, lists urinary incontinence as a common side effect occurring in 1% to 10% of users. Urinary frequency, difficulty urinating, and bedwetting are also reported at similar rates.
Cyclobenzaprine (sold as Flexeril and Amrix) works differently. It has anticholinergic properties, meaning it blocks certain nerve signals to muscles, including the bladder wall. The FDA label for cyclobenzaprine warns about urinary retention (inability to fully empty the bladder) and lists urinary frequency and retention among its reported side effects. When the bladder can’t empty completely, it can overflow, causing a type of leakage called overflow incontinence, where small amounts of urine dribble out because the bladder is constantly too full.
Overflow Incontinence From Urinary Retention
This distinction matters because some muscle relaxers don’t directly cause leakage. Instead, they prevent the bladder from contracting properly, leading to incomplete emptying. Over time, the bladder fills beyond its capacity, and urine spills out involuntarily. This overflow incontinence can feel confusing because you may have trouble starting a stream when you try to go, yet still experience leaking between bathroom trips.
Cyclobenzaprine and other muscle relaxers with anticholinergic effects are the most likely culprits here. The FDA specifically recommends caution when prescribing cyclobenzaprine to anyone with a history of urinary retention. If you notice that you’re straining to urinate, producing a weak stream, or feeling like your bladder never fully empties while taking one of these medications, those are signs of retention that could progress to overflow leaking.
Who Faces the Highest Risk
A large analysis of FDA adverse event reports identified several factors that make drug-induced urinary incontinence more likely. Women are significantly more affected than men, partly because pregnancy and childbirth can weaken pelvic floor structures that are then further compromised by a muscle relaxer. The risk also increases progressively with age, as the muscles and nerves controlling the bladder naturally lose some function over time.
Higher body weight is another independent risk factor. Certain medical conditions also raise vulnerability: Parkinson’s disease, seizure disorders, osteoporosis, depression, schizophrenia, and gastroesophageal reflux disease were all associated with a greater likelihood of developing incontinence while on medications that affect bladder function. Many of these conditions involve either nerve damage, chronic medication use, or both, which compounds the effect of adding a muscle relaxer.
For older adults specifically, the benzodiazepine data is striking. In a community study, 38% of people aged 75 and older reported urinary incontinence, and benzodiazepine use was a significant contributor. The longer these drugs stay in an older person’s system (which happens naturally because metabolism slows with age), the greater the impact on bladder control.
What Happens When You Stop the Medication
Drug-induced incontinence is generally reversible. Once you stop taking the muscle relaxer or switch to a different medication, bladder function typically improves. The timeline depends on the specific drug and how long it takes your body to clear it. Short-acting medications may stop causing symptoms within a day or two, while long-acting benzodiazepines or drugs that have built up in your system over weeks of use can take longer to wash out.
If you’re experiencing new or worsening bladder symptoms after starting a muscle relaxer, the most useful step is to identify whether the timing matches when you began the medication. Keep in mind that overflow incontinence from urinary retention can develop gradually, so the connection isn’t always obvious. A simple post-void residual test, where a clinician checks how much urine remains in your bladder after you urinate, can quickly clarify whether retention is the underlying issue.
Switching to a muscle relaxer with a different mechanism, choosing a shorter-acting drug, or adjusting the dose can often preserve the pain relief or spasm control you need while reducing the bladder side effects. The key is recognizing that the incontinence is medication-related rather than a new, unrelated problem, because that changes the solution entirely.