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 BRAND NAMES
 MECHANISM OF ACTION
The physiological mechanism responsible for erection of the penis involves the release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.
Phosphodiesterase type 5 (PDE5) is the enzyme responsible for degradation of cGMP
Tadalafil, is an inhibitor of phosphodiesterase type 5 (PDE5). When sexual stimulation causes local release of NO, inhibition of PDE5 by Tadalafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Tadalafil at recommended doses has no effect in the absence of sexual stimulation.
Tadalafil is rapidly absorbed with the maximum plasma concentration occurring at 2 hours. The earliest significant time from dosing to erectogenic effect is 16 minutes with tadalafil 20 mg, and 30 minutes with the dose of 10 mg. Tadalafil has an extended terminal half-life of approximately 17.5 hours, with an effectiveness lasting up to 36h 
- Tadalafil is indicated in adult men with erectile dysfunction, which is the inability to achieve or maintain a penile erection sufficient for satisfactory sexual performance. (Cialis)
- Treatment of the signs and symptoms of benign prostatic hyperplasia (Cialis)
- Treatment of erectile dysfunction and the signs and symptoms of benign prostatic hyperplasia (ED/BPH) (Cialis)
- Treatment of pulmonary arterial hypertension (See Adcirca)
- Erectile Dysfunction:
- For use as needed: Starting dose is 10 mg, 30 minutes prior to sexual activity. Increase to 20 mg or decrease to 5 mg based upon efficacy/tolerability.
- For once daily use: 2.5 mg taken once daily, without regard to timing of sexual activity. May increase to 5 mg based upon efficacy and tolerability
- Benign Prostatic Hyperplasia: 5 mg, taken at approximately the same time every day
- Erectile Dysfunction and Benign Prostatic Hyperplasia: 5 mg, taken at approximately the same time every day.
Tadalafil may be taken without regard to food
The maximum dose frequency is once per day.
- Tadalafil potentiate the hypotensive effects of nitrates and its administration in patients who use nitric oxide donors or nitrates in any form is therefore contraindicated.
- History of known serious hypersensitivity reaction to Tadalafil
- In men for whom sexual activity is inadvisable (e.g.Patients with severe cardiovascular disorders such as unstable angina or severe cardiac failure)
- Patients who have loss of vision in one eye because of non-arteritic anterior ischaemic optic neuropathy (NAION)
- Tadalafil has systemic vasodilatory properties and may augment the blood pressure lowering effect of anti-hypertensive medications.
- Seek emergency treatment for prolonged erections greater than 4 hours and priapism
- Caution is advised when Tadalafil is used as a treatment for Erectile dysfunction in men taking alpha blockers.
- CYP3A4 inhibitors: For concomitant use with potent CYP3A4 inhibitors (e.g. Ritonavir, atazanavir, clarithromycin, indinavir, itraconazole, nefazodone, nelfinavir, saquinavir, ketoconazole, telithromycin), dose adjustment may be needed. (Potent CYP3A4 inhibitors increase Tadalafil plasma levels)
- Alpha-blockers: Tadalafil is not recommended in combination with alpha blockers (e.g. Alfuzosin, Doxazosin, Tamsulosin...). In some patients, concomitant use of these two drug classes can lower blood pressure significantly leading to symptomatic hypotension.
- Tadalafil may augment the blood pressure lowering effect of anti-hypertensive medications.
 PREGNANCY AND LACTATION
Pregnancy Category B (US). Tadalafil (Cialis) is not indicated for use in women.
 SIDE EFFECTS
Most common adverse reactions (≥2%) include: headache, dyspepsia, back pain, myalgia, nasal congestion, flushing, and pain in limb
 RELATED LINKS
|Benign Prostatic Hypertrophy|
|5α reductase inhibitors||Dutasteride (Avodart) • Finasteride (Proscar)|
|Alpha 1 antagonists||Alfuzosin (Uroxatral, Xatral) • Doxazosin (Cardura) • Prazosin • Silodosin (Silodyx, Rapaflo) • Tamsulosin (Omnic, Flomax, Secotex) • Terazosin (Hytrin)|
|Phytotherapy||Pygeum africanum • Serenoa repens|
|PDE5 inhibitors||Tadalafil (Cialis)|
|Combination products||Dutasteride/Tamsulosin (Combodart, Jalyn, Duodart)|