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© The Canadian Journal of Urology™; 18(Supplement 1); April 2011
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first generation alpha blockers. Third generation
medications (tamulosin [Flomax CR], alfuzosin [Xatral
(Canada), Uroxatral (US)], and silodosin [Rapaflo, US
only]) do not require titration and have been found
to be more uroselective than their second generation
counterparts.
9
Silodosin [Rapaflo] was approved by
the US Food and Drug Administration (FDA) in 2008
and represents the latest alpha receptor blocker drug
available for use inmenwith sBPH. All third generation
alpha blockers have fewer cardiovascular side effects
compared to first and second generation alpha blockers
but may cause anejaculation or retrograde ejaculation.
12
Physicians must be aware that these drugs should be
taken after meals to improve absorption andmaximize
therapeutic efficacy.
Intraoperative floppy iris syndrome (IFIS) continues
to be discussed as an uncommon side effect of alpha
blocker therapy in men undergoing cataract surgery.
IFIS is thought to be secondary to an interaction
between all alpha blockers including tamsulosin,
terazosin, doxazosin, and alfuzosin, and alpha
1
ARs in the iris.
13
This may lead to an increased risk
of surgical complications from cataract surgery.
Patients with cataracts must be informed of these
risks prior to starting alpha blocker therapy and may
benefit from avoiding initiation of therapy until any
planned cataract surgery is completed. Unfortunately,
stopping alpha blockers does not always prevent the
occurrence of IFIS in those who go on to have cataract
surgery (up to 75% still present with IFIS). In June
2009, the American Academy of Ophthalmology
and the American Society of Cataract and Refractive
Surgery released their most current recommendations
for patients taking alpha blockers and IFIS and are
summarized in Table 2.
5-alpha reductase inhibitors
Prostatic glandular enlargement can lead to sBPH and
bothersome LUTS. As previously discussed, gland
growth and enlargement are under control of DHT
via the isoenzymes 5-alpha reductase types I and II.
The 5-alpha reductase inhibitors (5-ARI) finasteride
[Proscar] and dutasteride [Avodart] have been shown
to reduce prostate size and improve sBPH, Table 3.
Finasteride specifically inhibits the type II
isoenzyme leading to decreases in serum DHT by
70%-90%. Over a 6-12 month period the prostate size
can be reduced by 20%-30%.
14
Dutasteride blocks
both type I and type II 5-alpha reductase leading to
elimination of DHT to levels near zero in the serum.
14
Unfortunately, 5-ARIs can lead to decreased libido,
sexual dysfunction, gynecomastia, and male breast
tenderness. Both medications demonstrate similar
efficacy and tolerability, and should not be handled
by women of childbearing age as they are teratogenic.
Additionally, both finasteride and dutasteride can be
prescribed for prostate related bleeding as they inhibit
microvascular proliferation (block vascular endothelial
growth factor) and can be an effective treatment for
refractory hematuria secondary to prostatic bleeding.
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TABLE 1.
Alpha blockers for symptomatic benign prostatic hyperplasia (sBPH)
Name (Brand)
Dose
Side effects/Notes
Second generation
Terazosin
1 mg-10 mg daily*
First dose syncope; dizziness; tachycardia;
(Hytrin)
hypotension; headache; asthenia; rhinitis
Doxazosin
1 mg-8 mg daily*
Same as above
(Cardura)
Third generation
Alfuzosin
10 mg daily with food
Dizziness; headache; minimal cardiovascular
(Xatral [Canada]
effect; less ejaculatory dysfunction than
Uroxatral [US])
tamsulosin
Tamsulosin
Flomax CR: 0.4 mg daily
Ejaculatory dysfunction; rhinitis
(Flomax CR,
(with or without food)
generic capsules)
Generic capsules:
0.4 mg-0.8 mg daily with food
Silodosin
8 mg daily;
Retrograde ejaculation
(Rapaflo [US, not Canada]) 4 mg daily with CrCl 30-50 mL/min
*Dose titrated weekly to desired response, monitor blood pressure
LIU ET AL.