Pharmacology of the Bladder and Emerging Treatments

The nervous mechanisms for bladder emptying and urine storage involve a complex pattern of afferent and efferent signaling in parasympathetic, sympathetic, and somatic nerves. During voiding, contraction of the detrusor muscle is preceded by a relaxation of the outlet region, thereby facilitating the bladder emptying. Kim et al. found that 14 of 31 patients with overactive bladder (OAB) and nocturia, refractory to antimuscarinic treatment, improved with oral gabapentin. Ansari et al. treated children with refractory OAB symptoms with gabapentin as an add-on and found the drug to give modest positive results. The NK1-receptor antagonist, netupitant, decreased the frequency of reflex bladder contractions without altering their amplitude, suggesting that this drug targets the afferent limb of the micturition reflex circuit and therefore may be useful clinically in treating bladder overactivity symptoms. Possible peripheral targets for pharmacological intervention may be the efferent neurotransmission, the smooth muscle itself, including ion channels and intracellular second messenger systems, and the afferent neurotransmission.