SILDENAFIL PHARMATHEN FILM-COATED TABLET 50MG

Sildenafil

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

1-((3-(4,7-Dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo(4,3-d)pyrimidin-5-yl)-4-ethoxyphenyl)sulfonyl)-4-methylpiperazine | Sildenafil |

Description

Sildenafil is a vasoactive agent used to treat erectile dysfunction and reduce symptoms in patients with pulmonary arterial hypertension (PAH). Sildenafil elevates levels of the second messenger, cGMP, by inhibiting its breakdown via phosphodiesterase type 5 (PDE5). PDE5 is found in particularly high concentrations in the corpus cavernosum, erectile tissue of the penis. It is also found in the retina and vascular endothelium. Increased cGMP results in vasodilation which facilitates generation and maintenance of an erection. The vasodilatory effects of sildenafil also help reduce symptoms of PAH.

Indication

For the treatment of erectile dysfunction and to relieve symptoms of pulmonary arterial hypertension (PAH).

Mechanism of Action

Sildenafil 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 sildenafil enhances erectile function by increasing the amount of cGMP.

Pharmacodynamics

Erections are controlled by the parasympathetic nervous system. Upon sexual stimulation, a decrease in vascular resistance is mediated by acetylcholine and nitric oxide resulting in vasodilation. The hemodynamic mechanism of an erection is comprised of five stages. During the latent stage, arterial and carvernous smooth muscle relaxation occurs. Vasodilation results in high levels of blood flow causing the penis to grow to its full size. This stage is called tumescence. During the full-erection stage, blood flow fills penis sinusoids and outflow is restricted. This is followed by the rigid-erection phase during which the cavernous muscles contract causing the penis to become rigid. Little blood flow occurs during this stage. During the final stage, detumescence, the cavernous muscles relax and blood flows out of the penis. Erectile dysfunction may occur when there is insufficient blood supply to the penis or when the penis is unable to prevent outflow of blood from the penis. Sildenafil is a specific inhibitor of PDE5, an enzyme responsible for the breakdown of cGMP to 5’-GMP. Increased levels of cGMP stimulate vasodilation and facilitate the generation and maintenance of erections. These vasodilatory effects also help decrease symptoms of PAH. Sildenfail also exhibits some activity against PDE6 (10 times less potentcy compared to PDE5), a PDE isoform found predmoninantly in the retina. This activity is responsible for the blue tinged vision experienced by users of sildenafil.

Pharmacokinetics

Absorption:

>90% absorbed with ~40% reaching systemic circulation unchanged following first-pass metabolism

Distribution:

* 105 L

Metabolism:

Sildenafil appears to be completely metabolized in the liver to 16 metabolites. Its metabolism is mediated mainly by cytochrome P450 microsomal isozymes 3A4 (major route) and 2C9 (minor route). The major circulating metabolite, N-demethylated metabolite, has PDE selectivity similar to the parent drug and ~50% of its in vitro potency. The N-demethylated metabolite is further metabolized to an N-dealkylated N,N-de-ethylated metabolite. Sildenafil also undergoes N-dealkylation followed by N-demethylation of the piperazine ring.

Elimination:

Sildenafil is cleared predominantly by the CYP3A (major route) and cytochrome P450 2C9 (CYP2C9, minor route) hepatic microsomal isoenzymes. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose).

Half-life

4 hours

Clearance

Not Available

Toxicity

Not Available

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

Although best effort has been made to ensure the information provided is correct and updated, users are advised to visit HSA Official website whenever in doubt. Please see Disclaimers.
We welcome all the content error reporting/feedback. Please contact us @ Text Us!

Approval Information

SILDENAFIL PHARMATHEN FILM-COATED TABLET 50MG was registered with Health Science Authority of Singapore by GOLDPLUS UNIVERSAL PTE LTD. It is marketed with the registration number of SIN15175P with effective from 2017-02-14.

This product contains 50mg of Sildenafil in the form of TABLET, FILM-COATED.

The medicine was manufactured by Jubilant Generics LTD in INDIA

It is a Presciption Only Medicine which can only be obtained from a doctor or a dentist, or from a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Anatomical Therapeutic Chemical (ATC) Classification

ATC Code: G04BE03

Products Containing as Single Ingredient

Drug ID Trade Name Active Ingredients Forensic Class Registrant Status
1 DEXTROMETHORPHAN LINCTUS 15mg/5ml Dextromethorphan P Only DRUG HOUSES OF AUSTRALIA PTE LTD Active
22 ZENMOLIN SYRUP 2mg/5ml Salbutamol P Only DRUG HOUSES OF AUSTRALIA PTE LTD Active
41 APO-PROPRANOLOL TABLET 40mg Propranolol POM PHARMAFORTE SINGAPORE PTE LTD Active
42 APO-DIAZEPAM TABLET 2mg Diazepam POM PHARMAFORTE SINGAPORE PTE LTD Active
44 APO-DIAZEPAM TABLET 5mg Diazepam POM PHARMAFORTE SINGAPORE PTE LTD Active
45 APO-DIAZEPAM TABLET 10mg Diazepam POM PHARMAFORTE SINGAPORE PTE LTD Active
46 APO-PROPRANOLOL TABLET 10mg Propranolol POM PHARMAFORTE SINGAPORE PTE LTD Active
55 APO-ISDN TABLET 10mg Isosorbide Dinitrate POM PHARMAFORTE SINGAPORE PTE LTD Active
63 DIAPO TABLET 10mg Diazepam POM BEACONS PHARMACEUTICALS PTE LTD Active
64 FURMIDE TABLET 40mg Furosemide POM BEACONS PHARMACEUTICALS PTE LTD Active

Products Containing as Mixture Ingredient

Drug ID Trade Name Active Ingredients Forensic Class Registrant Status
5 DIPHENHYDRAMINE EXPECTORANT PAED. Ammonium Chloride|Diphenhydramine|Sodium Citrate P Only DRUG HOUSES OF AUSTRALIA PTE LTD Active
400 FAKTU SUPPOSITORY Cinchocaine|Policresulen P Only TAKEDA PHARMACEUTICALS (ASIA PACIFIC) PTE LTD Active
407 TRIMAXAZOLE TABLET Sulfamethoxazole|Trimethoprim POM BEACONS PHARMACEUTICALS PTE LTD Active
435 APO-SULFATRIM TABLET Sulfamethoxazole|Trimethoprim POM PHARMAFORTE SINGAPORE PTE LTD Active
508 APO-SULFATRIM PEDIATRIC TABLET Sulfamethoxazole|Trimethoprim POM PHARMAFORTE SINGAPORE PTE LTD Active
526 B.S. SUSPENSION Sulfamethoxazole|Trimethoprim POM APEX PHARMA MARKETING PTE LTD Active
583 CO-TRIMEXAZOLE SUSPENSION Sulfamethoxazole|Trimethoprim POM BEACONS PHARMACEUTICALS PTE LTD Active
676 BANEOCIN OINTMENT Bacitracin|Neomycin POM NOVARTIS (SINGAPORE) PTE LTD Active
678 BANEOCIN POWDER Bacitracin|Neomycin POM NOVARTIS (SINGAPORE) PTE LTD Active
706 TIENAM 500 FOR INJECTION Imipenem|Cilastatin POM MSD PHARMA (SINGAPORE) PTE LTD Active