Drugs Used In Prostatic Hyperplasia and Erectile Dysfunction

Drugs Used in Benign Enlargement of Prostate

Principle:  

Capsular and stromal tissue of Prostate gland is rich in α1 adrenoceptors, and glandular tissue under the influence of androgens. Both these, the α receptors and androgens, and androgens, are targets for drug therapy. Because the bladder itself has a few α receptors, it is possible to use selective α1-blockade without affecting bladder contraction.

Drugs:

α –adrenoceptor blockers:

•     Prazosin
•     Alfuzosin
•     Indoramin
•     Terazosin
•     Doxazosin
•     Tamsulosin

All are selective for α1 receptor.

Others:

•     Finasteride

Mechanism of drugs used in BHP: 

α1 receptor blockers cause significant increases (compared to placebo) in objective measures such as maximal urine flow rate and drugs also improve semi-objective symptom scores. In normotensive men, falls in blood pressure are generally negligible; in hypertensive patients, the decline in pressure can be regarded as an added bonus.

Tamsulosin is a competitive α1 receptor blocker with a structure quite different from that of most other α1 receptor blockers. Long half life of 9-15 hrs. it has higher affinity for α1A and α1D receptors than for the α1B subtype.

Advantages of tamsulosin over other alfa receptor blockers:

•     Long half life
• Greater potency in inhibiting contraction in prostate smooth muscle versus vascular smooth muscle
• Drug efficacy in BHP suggests that the α1A subtype may the most important alfa subtype mediating prostate smooth muscle contraction.
• Less effect on standing blood pressure

Adverse effects:

• Dizziness
• Asthenia
• Nasal stuffiness

But Tamsulosin has fewer side effects.

Finasteride: 

An alternative drug is the type II 5α-reductase inhibitor; it inhibits conversion of testosterone to its more potent metabolite, dihydrotestosterone.  It doesn’t affect serum testosterone, or most non-prostatic responses to testosterone. It reduces prostatic volume by 20% and increases urinary flow rates by a similar degree.

Drug used in erectile dysfunction:

• Sildenafil
• Tadalafil
• Vardenafil

Sildenafil
Mechanism of action:

Erectile response mediated by release of nitric oxide (NO) from nerves supplying vessels in corpora cavernosa. This increases intracellular cGMP levels which cause vasodilatation. Effects terminated by phosphodiesterase type 5 enzymes. Which is inhibited selectively by sildenafil, which enhances vasodilatory action of NO.

Contra indications:

• Severe hepatic impairment
• BP<90/50 mmHg
• Recent stroke or MI
• Patient who are taking organic nitrates

Adverse effects:

• Headache
• Flushing
• Dyspepsia
• Nasal congestion
• Green / blue tingling of vision (3%)

Drugs used for osteoporosis:

• Alendronate
• EtidronateIbandronate
• Pamidronate
• Risedronate

Drugs for obesity:

• Orlistat
• Phentermine
• Sibutramine