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Alpha-Blocker Therapy in the Management of Urological Disorders

Activation of Alpha adrenergic receptors for smooth muscles causes the smooth muscle to contract. Alpha blockers, therefore, produce smooth muscle relaxation by inhibiting contraction of this type of muscle. There are multiple types of alpha receptors resulting in different levels of selectivity of the alpha blockers.

Terazosin and Doxazosin are both non-selective alpha blockers, require dose titration, and have increased side effect of lightheadedness and a drop in blood pressure. Tamsulosin (Flomax) and its sister drug, Uroxatral (Alfuzosin), are moderately uro-selective and have less effect on blood pressure but can be associated with altered ejaculation. Silodosin (Rapaflo) is even more uro-selective, also alters ejaculation, and reportedly has a quicker onset of action. Reportedly, all are of relative equal efficacy, however, Rapaflo, again, has a shorter onset of action (3-4 hours). Regulation of bladder storage and voiding involves both sympathetic and parasympathetic control. Bladder voiding is primarily regulated by the parasympathetic nervous system via the neurotransmitter acetylcholine. Muscarinic receptors (M1-M3-M5) are mediated by acetylcholine in controlling the contraction of the bladder muscle and relaxation of the internal sphincter to facilitate voiding.

Indications

BPH/Lower Urinary Tract Symptoms (LUTS): Alpha blockers have been shown to improve urinary symptoms by virtue of relaxation of the smooth muscle of the prostate and the bladder neck. This results in an increase in urinary flow, decrease in urinary dribbling, decrease in residual volume, and can improve urinary frequency and urgency.
Acute urinary retention: A recent randomized placebo controlled study using Rapaflo vs placebo for three days in men with acute urinary retention (AUR) saw more than twice the number of men on Rapaflo being able to void successfully over placebo. This is certainly something to keep in mind for your men who go into acute urinary retention or in those who you are concerned may do so.
Non-bacterial, non-inflammatory prostatitis: Many men previously diagnosed and/or treated with antibiotics for prostatitis, also known as chronic pelvic pain syndrome indeed, may not have a bacterial source. For many of these men, alpha blockers can produce significant relief of many of the urinary tract symptoms present with this condition, especially when used in conjunction with hot baths and anti-inflammatories such as Advil.
Ureteral calculi: Although an off- label use, numerous studies show an increased spontaneous passage of stones with the use of alpha blockers (Medical Expulsion Therapy - EMT). Please see prior email on "Tis the Season" for further information. The one point to bring up is the fact that the most rapid onset drug available (Rapaflo) should be tried since it is more likely to be successful, whereas, Flomax can take 5 to 7 days to produce adequate effects.
Women with feelings of incomplete emptying and slow flow (many of whom in the old days used to be described as having urethral syndrome) can have marked improvement of their symptoms with the use of alpha blockers. Again, this is an off- label use, but certainly something to consider

There are no studies showing that alpha blockers can be used safely in the pediatric population and certainly we would not recommend it.

CAUTION: Associated with the use of alpha blockers, there is a syndrome called Floppy Iris Syndrome. This can result in drop in miosis, billowing of the flaccid iris, and iris prolapse during cataract surgery. Men with planned cataract surgery should avoid the initiation of alpha blockers until surgery is completed. Floppy Iris Syndrome appears to be lower with older, generic alpha blockers. Whether the dose/duration or cessation of treatment preoperatively affects floppy iris is unclear. It is important for all patients on alpha blockers to inform their ophthalmologists of the fact, although, certainly, ophthalmologists should be well aware of this issue.

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