«-Antagonists. The receptors responsible for maintaining smooth muscle tone in the prostate are a1A-ad-renoceptors, and it is in part due to failure of the prostatic smooth muscle to relax effectively that voiding is obstructed in BOO caused by BPH, leading in some to AUR, possibly as a result of excess stimulation of the a-adrenoceptors as a precipitative event.

There has been a large shift in recent years in the management of uncomplicated AUR. Previously, the majority of patients would have undergone transure-thral resection of the prostate (TURP) either in the acute setting or several weeks from initial presentation. The advent of -adrenoceptor antagonists has meant that a lot of patients who previously would have undergone surgery can be managed conservatively for a period of time. Standard policy has become starting a-an-tagonists at presentation, at least 24 h prior to TWOC, with very good outcomes. In patients presenting routinely with LUTS suggestive of BPH and BOO, significant symptomatic improvements are seen within 24-48 h of commencing a-antagonist therapy (Fitzpatrick and Kirby 2006; Chapple 2001; Andersson et al. 2002; Chapple 2004; Djavan et al. 2004; Elhilali et al. 2006).

Commonly used examples include doxazosin, pra-zosin, terazosin, indoramin (used less than previously), alfuzosin, and tamsulosin. The latter two are associated with fewer systemic side effects. Alfuzosin is to date the only member of this class of drugs to have statistically proven benefits in aiding TWOC in patients with episodes of AUR (Elhilali et al. 2006; Roehrborn 2006a; McNeill et al. 1999), although it is likely that similar efficacy would be expected to be present for the other agents in the class.

Several studies have shown benefits in terms of prolonging time to retention or surgery, and recent studies have compounded these benefits by using combination therapy with 5a-reductase inhibitors (McConnell et al. 2003).

5a-Reductase Inhibitors. The 5a-reductase inhibitors work by inhibiting the enzyme responsible for converting testosterone into the more active form DHT. There are two commercially available examples, finasteride and dutasteride. The method of action is to reduce the effect of circulating androgens on the prostate. They effectively reduce growth of the prostate, and have been shown to shrink the glandular component of histological BPH. They are most effective in large prostate glands, but unfortunately the beneficial effects take approximately 4-6 months to appear, so their use in the short term is of limited value. However, if a patient presents with a large volume gland causing BPE and AUR, then adding in a 5a-reductase inhibitor to a-an-tagonist therapy will prolong the time to further episodes of AUR and the need for surgical intervention (McConnell et al. 2003; Andriole et al. 2004; Kaplan et al. 2006).

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