🔴 Mechanism of Action 🔴

🔺1. Antiandrogens :-

a. Flutamide :- Non-steroidal AR (androgen receptor)antagonist with no other hormonal activity.
They are now used in conjunction with GnRH agonist or after castration to block the residual action of adrenal androgens as COMBINED ANDROGEN BLOCKED (CAB) therapy of metastatic carcinoma prostate.

b. Bicalutamide :- more potent and linger acting (half life is 6 days) congener of flutamide.

🔺2. 5-alpha reductase inhibitors
(e.g. Finasteride and Dutasteride)

These drugs are competitive inhibitor of 5 aloha reductase enzyme which converts the Testosterone intomore active Dyhydrotestosterone and gives androgenic action in many tissues.... So, these drugs reduce this effect by blocking the 5-alpha reductase enzyme.

🔺Note...
Finasteride selectively inhibit type 2 isoenzyme 5-alpha reductase.

Dutasteride inhibit both type 1 and type 2 isoenzymes (5-alpha reductase) and inhibit DHT levels.

🔴ADRS OF ANTIANDROGENS🔴
✔️Androgenic anabolism is suppressed
✔️Gynacosmastia
✔️Breast tenderness
✔️Liver damage occures frequently
✔️Skin rashes
✔️Swelling of lips

🔴 Mechanism of Action 🔴

🔺 Drugs for erectile dysfunction :-

🔺How normal erection of penis takes place??? .... When sexual arousal then increases blood flow to the penis and relaxes the cavernosal sinusoids so that they fill up with blood, making the penis rigid, elongated and erect. Nitric oxide (NO) released from parasympathetic nonadrenergic noncholinergic (NANC) nerves and vascular endothelium is the major transmitter causing relaxation of smooth muscle in corpus cavernosum and the blood vessels supplying it; Ach and PGs also play a role.

1. Androgens :-

Hypogonadism is an infrequent cause if ED (erectile dysfunction) . Parenteral testosterone esters or transdermal testosterone therapy is effective only when androgen deficiency is proven to be responsible for loss of libido and erectile dysfunction.

2. Phosphodiesterase-5 (PDE-5) inhibitors :-

NO (Nitric Oxide) causes smooth muscle relaxation by generating cGMP intracellularly..... Promote dephosohorylation of myocin light chain kinase ( MLCK) .... so that myocin interact with actin. Inhibition of PDE-5 is degrading isoenzyme is cavernisal and vascular smooth muscle, results accumulation if cGMP and marked potentiation of NO action.

e.g. Sildenfil, Vardenafil & Tadalafil . Are selective PDE-5 inhibitors found effective in majority of patients.

3. Papaverine /phentolamine induced penile erection (PIPE) therapy.:- (Use these only in cases not responding to sildenfil and alprostadil.

4.Prostaglandin E1 :-
( Use by directly injectin into Corpus cavernosum)

🔴ADRS OF PDE5 INHIBITORS 🔴
✔️Headache
✔️Nasal congestion
✔️Dizziness
✔️Facial flushing
✔️Fall bp
✔️Impairment of colour vision specially blue n green discrimination
✔️Gastric reflux and dyspepsia
✔️