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Products > Human Product > Other > Tadalafil

Tadalafil


Category:

Erectile dysfunction treatment .

Composition :

Each film coated tablet contains 10 mg of Tadalafil .

Chemistry :

The chemical name of tadalafil is (6R, 12aR)-2,3,6,7,12,12a-Hexahydro-2-methyl-6-[3,4-(methylenedioxy)phenyl]-pyrazino[1',2':1,6] pyrido[3,4-b] indole-1,4-dione. The molecular formula is C22H19N3O4 and molecular weight is 389.41.

Mechanism of Action :

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 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) enhances erectile function by increasing the amount of cGMP. Tadalafil inhibits PDE5. Because sexual stimulation is required to initiate the local release of nitric oxide, the inhibition of PDE5 by Tadalafil has no effect in the absence of sexual stimulation . [PDR 2007]

Pharmacokinetics :

Tadalafil is well absorbed after a dose by mouth . Peak plasma concentration are attained within 2 hours . The rate of absorption is not affected by food. Tadalafil is widely distributed into tissues and is approximately 94% bound to plasma proteins . It is metabolised in the liver primarily by the cytochrome P450 isoenzyme CYP3A4 . The major metabolite, the methylcatechol glucuronide, is inactive . The mean half- life of Tadalafil is about 17.5 hours . Tadalafil is excreted, predominantly as metabolites, in the feces (61% of the dose ) and to a lesser extent the urine (36% of the dose) . Clearance may be reduced in the elderly and in patients with renal impairment . [Martindale 2007]

Indications :

Tadalafil is indicated for the treatment of erectile dysfunction. [PDR 2007]

Precautions :

Tadalafil should be used with caution in cardiovascular diseases, anatomical deformation of the penis (e.g.angulation, cavernosal fibrosis, peyronie’s disease) and in those with a predisposition to prolonged erection. Tadalafil also should be used with caution in hepatic and renal impairment . [BNF 2006]

Pregnancy :

There are no adequate and well controlled studies of Tadalafil in pregnant women . It is not indicated for use in women . [PDR 2007]

Breast feeding :

Use of Tadalafil in nursing mothers is not recommended . [PDR 2007]

Drug interactions :

- Cytochrom P450 inhibitors : Ketoconazole, HIV protease inhibitors (such as ritonavir), erythromycin, itraconazole, grapefruit juice . - Cytochrom P450 inducers : Rifampin, carbamazepine, phenytoin, phenobarbital - Antacids - Alcohol - Anti-hypertensives : α- blockers ( Doxazosin, Tamsulosin), Amlodipine, Metoprolol, Enalapril (PDR 2007)

Contraindications :

- Tadalafil is contraindicated for patients with a known hypersensitivity to Tadalafil or any component of the tablet . [PDR 2007] - Administration with nitrates and nitric oxide donors - Coadministration with alpha-blockers other than 0.4 mg/day Tamsulosin. [Fact 2007] - Hypotension , recent stroke, unstable angina , myocardial infarction, moderate heart failure , uncontrolled arrhythmias, uncontrolled hypertension. [BNF 2006]

Warnings :

- Priapism - Cardiovascular The following groups of patients with cardiovascular disease were not included in clinical safety and efficacy : - Patients with an MI within the last 90 days - Patients with unstable angina or angina occurring during sexual intercourse. - Patients with New York Heart Association class 2 or greater heart failure in the last 6 months . - Patients with uncontrolled arrhythmias , hypotension (BP less than 90/50 mm Hg) or uncontrolled hypertension (BP greater than 170/100 mm Hg) - Patients with a stroke within the last 6 months . [Fact 2007]

Adverse Reactions :

- Cardiovascular : Hypertension , MI - CNS : Dizziness - Dermatologic : Rash - GI : Diarrhea , gastroesophageal reflux, GGTP increased, loose stools, nausea , upper abdominal pain . - Gu : Erection increased, spontaneous penile erection . - Musculoskeletal : Arthralgia, neck pain . - Respiratory : Epistaxis , dyspnea , pharyngitis . Special senses : Conjunctivitis , eye pain , blurred vision , conjunctival hyperemia , eyelid swelling , lacrimation increased , change in color vision . Miscellaneous : Asthenia , face edema, pain, fatigue [Fact 2007]

Dosage and administration :

The recommended starting dose of Tadalafil in most patients is 10mg, taken prior to anticipated sexual activity . The dose may be increased to 20 mg or decreased to 5 mg, based on individual efficacy and tolerability . The maximum recommended dosing frequency is once per day . Tadalafil may be taken without regard to food . [PDR 2007]

Storage :

Store below 30° C. [PDR 2007]

How Supplied :

Tadalafil 10 mg is available as brown, barrel-shape film-coated tablet. There are blisters of 4’s, boxes of one blister.

References:

Martindale, 2007 PDR, 2007 Fact, 2007 USP DI, 2005 BNF, 2006
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