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:
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