Tadalafil is an orally administered drug used to treat male erectile dysfunction (impotence). It is marketed worldwide under the brand name Cialis. It is a phosphodiesterase 5 (PDE5) inhibitor.
Tadalafil's distinguishing pharmacologic feature is its longer half-life (17.5 hours) compared with Viagra and Levitra (4-5 hours). This longer half-life results in a longer duration of action and is, in part, responsible for the Cialis nickname of the "weekend pill." This longer half-life also is the basis of current investigation for tadalafil's use in pulmonary arterial hypertension as a once-daily therapy.
Tadalafil tablets are indicated for the treatment of: erectile dysfunction (ED), the signs and symptoms of benign prostatic hyperplasia (BPH), the signs and symptoms of BPH (ED/BPH).
Apcalis-SX, film-coated tablet, is swallowed with a glass of water one hour before planned sexual activity. It can be taken with or without a meal because a meal does not affect its absorption. However, the high fat meal may takes longer to work while it shows faster effects when taken on an empty stomach. Do not use it in combination with grapefruit juice to avoid health complications.
The usual adult dose of Apcalis-SX is 20 mg per day about an hour prior to a sexual act or as needed. The dose should not exceed more than 20 mg and should not be less than 10 mg per day. It should not be taken twice or more per day. The effect of the drug lasts for 24 hours to 36 hours that is why it is also called as “weekend tablet”.
Tadalafil is used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH). Part of the physiological process of erection involves the release of nitric oxide (NO) in the corpus cavernosum.
This then activates the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation in the corpus cavernosum, resulting in increased inflow of blood and an erection. Tadalafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum.
This means that, with tadalafil on board, normal sexual stimulation leads to increased levels of cGMP in the corpus cavernosum which leads to better erections. Without sexual stimulation and no activation of the NO/cGMP system, tadalafil should not cause an erection.
Tadalafil inhibits the cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum located around the penis. Penile erection during sexual stimulation is caused by increased penile blood flow resulting from the relaxation of penile arteries and corpus cavernosal smooth muscle.
This response is mediated by the release of nitric oxide (NO) from nerve terminals and endothelial cells, which stimulates the synthesis of cGMP in smooth muscle cells. Cyclic GMP causes smooth muscle relaxation and increased blood flow into the corpus cavernosum. The inhibition of phosphodiesterase type 5 (PDE5) by tadalafil enhances erectile function by increasing the amount of cGMP.
Metabolism: Tadalafil is predominantly metabolized by CYP3A4 to a catechol metabolite. The catechol metabolite undergoes extensive methylation and glucuronidation to form the methylcatechol and methylcatechol glucuronide conjugate, respectively. In vitro data suggests the metabolites are not expected to be pharmacologically active at observed metabolite concentrations.
Absorption: After single oral-dose administration, the maximum observed plasma concentration (Cmax) of tadalafil is achieved between 30 minutes and 6 hours (median time of 2 hours). Absolute bioavailability of tadalafil following oral dosing has not been determined.
Route of elimination: Tadalafil is excreted predominantly as metabolites, mainly in the feces (approximately 61% of the dose) and to a lesser extent in the urine (approximately 36% of the dose).
Half life: 17.5 hours
All medicines may cause side effects, but many people have no, or minor, side effects.Some medical conditions may interact with Tadalafil.
Tell your doctor or pharmacist if you have any medical conditions.
Common tadalafil side effects may include: headache, flushing (warmth, redness, or tingly feeling), nausea, upset stomach, stuffy nose; or muscle pain, back pain, pain in your arms or legs.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.