ATC Group: G04B Other urologicals, incl. antispasmodics

Acetohydroxamic acid (AHA) is a stable, synthetic compound derived from hydroxylamine and ethyl acetate. Its molecular structure is similar to urea. AHA reversibly inhibits the bacterial enzyme urease, thereby inhibiting the hydrolysis of urea and production of ammonia in urine infected with urea-splitting organisms. The reduced ammonia levels and decreased pH enhance the effectiveness of antimicrobial agents and allow an increased cure rate of these infections.

Alprostadil is chemically identical to prostaglandin E₁, the actions of which include vasodilatation of blood vessels in the erectile tissues of the corpora cavernosa and increase in cavernosal artery blood flow, causing penile rigidity.

Apomorphine is a direct stimulant of dopamine receptors and while possessing both D1 and D₂ receptor agonist properties does not share transport or metabolic pathways with levodopa. Its actions on parkinsonian motor disability are likely to be mediated at post-synaptic receptor sites.

Avanafil is a highly selective and potent, reversible inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5. When sexual stimulation causes the local release of nitric oxide, inhibition of PDE5 by avanafil produces increased levels of cGMP in the corpus cavernosum of the penis. This results in smooth muscle relaxation and inflow of blood into the penile tissues, thereby producing an erection.

Calcium is the most abundant mineral in the body, and is an essential body electrolyte. Homeostasis is mainly regulated by the parathyroid hormone, by calcitonin, and by the activated form of vitamin D. Calcium is a structural component of bones and teeth. It is also required for blood clotting, neurotransmitter release, muscle contraction and normal heartbeat.

Dapoxetine is a potent selective serotonin reuptake inhibitor (SSRI). The mechanism of action of dapoxetine in premature ejaculation is presumed to be linked to the inhibition of neuronal reuptake of serotonin and the subsequent potentiation of the neurotransmitter’s action at pre- and postsynaptic receptors.

Darifenacin is a selective muscarinic M3 receptor antagonist (M3 SRA) in vitro. The M3 receptor is the major subtype that controls urinary bladder muscle contraction. It is not known whether this selectivity for the M3 receptor translates into any clinical advantage when treating symptoms of overactive bladder syndrome.

Desfesoterodine is a competitive, specific muscarinic receptor antagonist. It is the primary active metabolite of fesoterodine, and regarded as main active pharmacological principle of fesoterodine; fesoterodine is considered as prodrug of desfesoterodine. The affinity of desfesoterodine for the muscarinic receptors is 2 orders of magnitude greater than that of fesoterodine.

Dimethyl sulfoxide is used for the symptomatic relief of patients with interstitial cystitis. There is no clinical evidence of effectiveness of dimethyl sulfoxide in the treatment of bacterial infections of the urinary tract.

Fesoterodine is a competitive, specific muscarinic receptor antagonist. It is rapidly and extensively hydrolysed by non-specific plasma esterases to the 5-hydroxymethyl derivative, its primary active metabolite, which is the main active pharmacological principle of fesoterodine.

Flavoxate is an antispasmodic selective to the urinary tract. Flavoxate has been shown to have a direct antispasmodic action on smooth muscle fibres.

Imidafenacin is an antagonist of muscarinic cholinergic receptors and used for treatments of overactive bladder. Imidafenacin antagonizes subtypes M3 and M1 in vitro. In the urinary bladder, imidafenacin inhibits acetylcholine release by antagonizing subtype M1 and contraction of smooth muscles by antagonizing subtype M3. Compared with the inhibitory effect on the salivary gland, imidafenacin shows higher inhibitory effect on the urinary bladder contraction, probably indicating efficacy and safety of these products in the clinical practice.

Magnesium hydroxide is practically insoluble in water and solution is not effected until the hydroxide reacts with hydrochloric acid in the stomach to form magnesium chloride. Its neutralising action is almost equal to that of sodium bicarbonate. When the dose is in excess of that required to neutralise the acid the intragastric pH may reach pH 8 or 9. Acid rebound following magnesium hydroxide is clinically insignificant. Magnesium hydroxide has an indirect cathartic effect resulting from water retention in the intestinal lumen.

Mirabegron is a potent and selective beta₃-adrenoceptor agonist. Mirabegron enhances urine storage function by stimulating beta₃-adrenoceptors in the bladder.

Oxybutynin acts as a competitive antagonist of acetylcholine at post-ganglionic muscarinic receptors, resulting in relaxation of bladder smooth muscle.

The hypothetic mechanism of action of pentosan polysulfate includes a local effect in the bladder after systemic administration and excretion into the urine by binding of glycosaminoglycans to the deficient mucous of the bladder. It is hypothesized, that a potential barrier function of pentosan polysulfate instead of the damaged urothelial mucus might play a role as well the antiinflammatory activity of pentosan polysulfate sodium.

Phenazopyridine is excreted in the urine where it exerts a topical analgesic effect on the mucosa of the lower urinary tract. This action helps to relieve pain, burning, urgency and frequency. The precise mechanism of action is unknown.

Propiverine inhibits calcium influx and modulates intracellular calcium in urinary bladder smooth muscle cells causing musculotropic spasmolysis. Also, it inhibits the efferent connection of the nervus pelvicus due to anticholinergic action.

Sildenafil is a potent and selective inhibitor of cyclic guanosine monophosphate (cGMP) specific phosphodiesterase type 5 (PDE5), the enzyme that is responsible for degradation of cGMP. Apart from the presence of this enzyme in the corpus cavernosum of the penis, PDE5 is also present in the pulmonary vasculature. Sildenafil, therefore, increases cGMP within pulmonary vascular smooth muscle cells resulting in relaxation.

Solifenacin is a competitive, specific cholinergic-receptor antagonist. In vitro and in vivo pharmacological studies indicate that solifenacin is a competitive inhibitor of the muscarinic M3 subtype receptor.

Tadalafil is a selective, reversible inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). When sexual stimulation causes the local release of nitric oxide, inhibition of PDE5 by tadalafil produces increased levels of cGMP in the corpus cavernosum. This results in smooth muscle relaxation and inflow of blood into the penile tissues, thereby producing an erection. The effect of PDE5 inhibition on cGMP concentration in the corpus cavernosum is also observed in the smooth muscle of the prostate, the bladder and their vascular supply. The resulting vascular relaxation increases blood perfusion which may be the mechanism by which symptoms of benign prostatic hyperplasia are reduced.

Tiopronin is similar to penicillamine in both chemistry and pharmacology and used to control the rate of cystine precipitation and excretion in the disease cystinuria. The drug works by reacting with urinary cysteine to form a more soluble, disulfide linked, tiopronin-cysteine complex

Tolterodine is a competitive, specific muscarinic receptor antagonist with selectivity for the urinary bladder over salivary glands in vivo.

Trospium is an antispasmodic, antimuscarinic agent indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and urinary frequency. Receptor assays showed that trospium has negligible affinity for nicotinic receptors as compared to muscarinic receptors at concentrations obtained from therapeutic doses. Trospium antagonizes the effect of acetylcholine on muscarinic receptors in cholinergically innervated organs. Its parasympatholytic action reduces the tonus of smooth muscle in the bladder.

Udenafil, an oral therapy for the treatment of erectile dysfunction (ED), is a pyrazolopyrimidinone class and a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5) of the corpus cavernosum, which induce potent penile erection.

Vardenafil is a potent and selective inhibitor of the cGMP specific phosphodiesterase type 5 (PDE5), the most prominent PDE in the human corpus cavernosum. Vardenafil is an oral therapy for the improvement of erectile function in men with erectile dysfunction. In the natural setting, i.e. with sexual stimulation it restores impaired erectile function by increasing blood flow to the penis.

Vibegron is a selective and potent human beta-3 adrenergic receptor agonist over β1-AR and β2-AR. Activation of the beta-3 adrenergic receptor located in the bladder detrusor muscle increases bladder capacity by relaxing the detrusor smooth muscle during bladder filling.