Source: Health Products Regulatory Authority (ZA) Revision Year: 2022 Publisher: GlaxoSmithKline Consumer Healthcare South Africa (Pty) Limited, 39 Hawkins avenue, Epping Industria 1, Cape Town, 7460
Pharmacotherapeutic group: Topical products for joint and muscular pain. Anti-inflammatory preparations, nonsteroids for topical use
ATC code: M02AA15
Pharmacological classification: A.3.1 Antirheumatic (anti-inflammatory agents)
Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) with pronounced analgesic, anti-inflammatory and antipyretic properties. Inhibition of prostaglandin synthesis is the primary mechanism of action of diclofenac.
Voltaren Emulgel 12 Hour is an anti-inflammatory and analgesic preparation designed for topical application. In inflammation and pain of traumatic origin, Voltaren Emulgel 12 Hour relieved pain, decreased swelling, and shortened the time to return to normal function. In one ankle sprain study (VOPO-P- 307), Voltaren Emulgel 12 Hour significantly decreased pain on movement scores versus placebo treated subjects within three days of starting treatment. In addition, treatment with Voltaren Emulgel 12 Hour also significantly improved ankle joint function within 3 days of beginning treatment.
Due to an aqueous-alcoholic base the gel also exerts a cooling effect.
The quantity of diclofenac absorbed through the skin is proportional to the size of the treated area; and depends on both the total dose applied and the degree of skin hydration. After topical application to approximately 400 cm² of skin, the extent of systemic exposure as determined by plasma concentration of Voltaren Emulgel 12 Hour (2 applications/day) was equivalent to diclofenac 1.16% gel (4 applications/day). The relative bioavailability of diclofenac (AUC ratio) for Voltaren Emulgel 12 Hour versus tablet was 4.5% on day 7 (for equivalent diclofenac sodium dose). Absorption was not modified by a moisture and vapour permeable bandage.
Diclofenac concentrations have been measured from plasma, synovial tissue and synovial fluid after application of topical diclofenac to hand and knee joints. Maximum plasma concentrations were approximately 100 times lower than after oral administration of the same quantity of diclofenac. 99.7% of diclofenac is bound to serum proteins, mainly albumin (99.4%).
Diclofenac penetrates inflamed areas, preferentially distributing to and persisting in deep inflamed tissues such as joints, where it is found in concentrations up to 20 times higher than in plasma.
Biotransformation of diclofenac 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 of the phenolic metabolites are biologically active, however, to a much smaller extent than diclofenac.
The total systemic clearance of diclofenac from plasma is 263 ± 56 ml/min. The terminal plasma half-life is 1-2 hours.
Four of the metabolites, including the two active ones, also have short plasma half-lives of 1-3 hours. One metabolite, 3'-hydroxy-4'-methoxy-diclofenac, has a longer half-life but is virtually inactive. Diclofenac and its metabolites are excreted mainly in the urine.
No accumulation of diclofenac and its metabolites is to be expected in patients suffering from renal impairment. In patients with chronic hepatitis or non-decompensated cirrhosis, the kinetics and metabolism of diclofenac are the same as in patients without liver disease.
Voltaren Emulgel 12 Hour was well tolerated in a variety of studies. There was no potential for phototoxicity and diclofenac containing gel caused no skin sensitisation or irritation.
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