Pharmacotherapeutic Group: ALPHA-BLOCKER. ATC code: G04CA01 (G: genitourinary system and sex hormones).
Pharmacology: Pharmacodynamics: Alfuzosin is an orally active quinazoline derivative. It is a selective antagonist of post-synaptic alpha-1 adrenoreceptors. Reported pharmacological studies conducted in vitro have confirmed the selectivity of alfuzosin for alpha-1 adrenoreceptors located in the prostate, bladder base and urethra.
Alpha-blockers decrease infravesical obstruction via direct action on prostate smooth muscle. In vivo studies in animals have reported that alfuzosin reduces urethral pressure thereby lowering resistance to urine flow during micturition. A study in awake rats reported a greater effect on urethral pressure than the effect on blood pressure.
Reported placebo-controlled studies in patients with benign prostatic hypertrophy showed that alfuzosin: significantly increases urine flow rate by a mean of 30% in patients with a flow rate of ≤ 15 ml/s. This improvement is observed from the first dose; significantly reduces detrusor pressure and increases volume, producing the desire to void; significantly reduces the residual urine volume.
These effects lead to an improvement in irritative and obstructive urinary symptoms. They have no negative effect on sexual function. Furthermore, maximum urinary flow rate remains significantly increased 24 hours after intake.
Pharmacokinetics: Alfuzosin hydrochloride is reported to be approximately 90% plasma protein binding. Alfuzosin is extensively metabolized in the liver with only 11% of the parent drug excreted in urine. Most of the metabolites (which are inactive) are reported to be excreted in the feces (75 to 90%). The pharmacokinetic profile of alfuzosin is unchanged in patients with chronic heart failure.
Studies have reported that the bioavailability is increased when the drug is administered after a meal (see DOSAGE & ADMINISTRATION). The pharmacokinetic parameters (Cmax and AUC) are not increased in the elderly as compared to middle-aged healthy volunteers.
The mean Cmax and AUC values are reported to be moderately increased in patients with moderately impaired kidney function (creatinine clearance > 30 ml/min), with no change in elimination half-life, as compared to patients with normal kidney function.
Dosage adjustment is, therefore, not necessary in patients with impaired kidney function with a creatinine clearance of > 30 ml/min.