Voltaren Emulgel

Voltaren Emulgel Mechanism of Action

diclofenac

Manufacturer:

GSK Consumer Healthcare

Distributor:

Zuellig
Full Prescribing Info
Action
Pharmacotherapeutic Group: Topical products for joint and muscular pain, anti-inflammatory preparations, nonsteroids for topical use.
Pharmacology: Pharmacodynamics: In inflammation of traumatic or rheumatic origin, Voltaren Emulgel has been shown to relieve pain, reduce edema and shorten the time needed to regain normal function.
Mechanism of Action: Diclofenac, the active substance of Voltaren Emulgel, is a nonsteroidal anti-inflammatory drug (NSAID) with pronounced antirheumatic, anti-inflammatory, analgesic and antipyretic properties.
Inhibition of prostaglandin biosynthesis by diclofenac has been demonstrated experimentally and is regarded as an important component of its mechanism of action.
Clinical Studies: Diclofenac is a well-established product.
Pharmacokinetics: Absorption: The amount of diclofenac absorbed through the skin is proportional to the contact time and skin area covered with Voltaren Emulgel, and depends on the total topical dose and the hydration of the skin. Absorption amounts to about 6% of the dose of diclofenac after topical application of Voltaren Emulgel 2.5 g/500 cm2 skin, determined by reference to the total renal elimination compared with Voltaren tablets. Occlusion over a period of 10 hrs leads to a 3-fold increase in the amount of diclofenac absorbed.
Distribution: After topical administration of Voltaren Emulgel to hand and knee joints, diclofenac can be measured in plasma, synovial tissue and synovial fluid. Maximum plasma concentrations (Cmax) of diclofenac after topical administration of Voltaren Emulgel are about 100 times lower than after oral administration of Voltaren tablets. Ninety-nine and seven tenths percent (99.7%) of diclofenac binds to serum proteins, chiefly to albumin (99.4%).
Diclofenac accumulates in the skin which acts as reservoir from where there is a sustained release of drug into underlying tissues. From there, diclofenac is preferentially distributed to and persists in deep inflamed tissues eg, the joint, where it is found in concentrations up to 20 times higher than in plasma.
Biotransformation/Metabolism: This involves partly glucuronidation of the intact molecule, but mainly single and multiple hydroxylation resulting in several phenolic metabolites, most of which are converted to glucuronide conjugates. Two (2) of these phenolic metabolites are biologically active, however, to a much smaller extent than diclofenac.
Elimination: The total systemic clearance of diclofenac from the plasma is 263±56 mL/min (mean value±SD). The terminal plasma t½ is 1-2 hrs. Four (4) of the metabolites, including the 2 active ones, also have short plasma t½ of 1-3 hrs. One (1) metabolite, 3'-hydroxy-4'-methoxy-diclofenac, has a much longer plasma t½, but is virtually inactive. Diclofenac and its metabolites are excreted mainly in the urine.
Special Populations: No accumulation of diclofenac or its metabolites is to be expected in patients suffering from renal impairment.
The kinetics and metabolism of diclofenac are the same in patients with chronic hepatitis or non-decompensated cirrhosis, as in patients without liver disease.
Toxicology: Nonclinical Safety Data: Preclinical data from acute and repeated-dose toxicity studies, as well as from genotoxicity, mutagenicity and carcinogenicity studies with diclofenac revealed no specific hazard for humans at the intended therapeutic doses. There was no evidence that diclofenac had a teratogenic potential in mice, rats or rabbits. Diclofenac had no influence on the fertility of parent animals in rats. The prenatal, perinatal and postnatal development of the offspring was not affected.
Voltaren Emulgel was well-tolerated in a variety of studies. There was no potential for phototoxicity and Voltaren Emulgel caused no skin sensitization.
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