Symptoms of urinary retention include the inability to urinate, which occurs when an individual is not fully able to empty his or her bladder, despite having the urge to urinate. Urinary retention may be an acute (happening suddenly) or longstanding (chronic) problem in both men or women and can be associated with other bladder problems or abnormalities within the pelvis. Urinary retention is more common in men than women and increases in frequency as men age. Any condition that results in a physical blockage of the urethra (the tube through which urine exits the bladder) can result in the inability to urinate. Another cause of urinary retention is a defect or disruption in the function of the nerves that control urination. Some medications can cause or worsen urinary retention. Examples of these include general anesthetic agents, stimulants such as pseudoephedrine (Sudafed and others) and phenylpropanolamine (Dexatrim and others), and antihistamines such as diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton).