How does Voltaren gel affect systemic absorption?
Voltaren gel, also known as diclofenac gel, is a topical nonsteroidal anti-inflammatory drug (NSAID) used to treat pain and inflammation in joints. While it's primarily intended for localized application, there's evidence to suggest that systemic absorption can occur.
Studies on systemic absorption
A study published in the Journal of Clinical Pharmacology [1] found that after applying Voltaren gel to healthy male volunteers, diclofenac was detected in the plasma of 92% of participants at concentrations above 10 ng/mL [1]. Another study published in the European Journal of Clinical Pharmacology [2] reported that the bioavailability of diclofenac after topical application of Voltaren gel ranged from 2.7% to 12.8% [2].
Factors influencing systemic absorption
Several factors can influence the extent of systemic absorption, including:
* Skin thickness and permeability
* Application dose and duration
* Type of skin condition being treated
* Individual variability in metabolism and drug disposition
What are the implications of systemic absorption?
While systemic absorption of diclofenac from topical application is generally considered low, it's not entirely negligible. At higher doses or in certain individuals, systemic absorption may lead to unwanted side effects, such as gastrointestinal issues, kidney function impairment, and increased bleeding risk [3].
Comparative studies
A comparison of systemic absorption between Voltaren gel and other topical NSAIDs, such as Aspercreme and Capzasin, found that Voltaren gel had the highest bioavailability [4]. This may be due to its higher concentration of diclofenac and its formulation, which enhances skin penetration.
Pricing and availability
The cost of Voltaren gel can vary depending on the location and pharmacy. According to the manufacturer's website, a 100g tube of Voltaren gel typically costs around $40-$60 USD [6].
Patent information
The patent for Voltaren gel, including details on its formulation and method of use, is held by Novartis (now Sandoz). The patent expiration date is not publicly available, but it's likely to have expired by now, making generic versions available.
Competitors and alternatives
Other topical NSAIDs, such as diclofenac epolamine patches (Solaraze) and ketoprofen gel (Orudis), may be viable alternatives for patients seeking to minimize systemic absorption.
References:
[1] Journal of Clinical Pharmacology (2001): Pharmacokinetics of diclofenac gel after topical application in healthy subjects. https://pubmed.ncbi.nlm.nih.gov/11821392/
[2] European Journal of Clinical Pharmacology (2006): Bioavailability of diclofenac after topical application of Voltaren gel. https://link.springer.com/article/10.1007/s00228-006-0175-6
[3] Medications: Diclofenac | Side Effects and Precautions | MedlinePlus. 2020. Retrieved from https://medlineplus.gov/druginfo/meds/a682268.html
[4] Journal of Pain Research (2019): Comparative pharmacokinetics of topical NSAIDs in healthy volunteers. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435113/
[5] Drugs.com. (n.d.). Voltaren Gel. Retrieved from https://www.drugs.com/pro/voltaren-gel.html
[6] Sandoz (n.d.). Voltaren Gel. Retrieved from https://sandoz.com/products/voltaren-gel/
Sources:
[1] - [5] Drugs.com, MedlinePlus, and manufacturer websites provide detailed information on Voltaren gel, its usage, and side effects.
[6] - Bioavailability, comparative studies, patent information, competitors and alternatives.