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Topical Analgesics: Critical Issues Related to Formulation and Concentration
Keppel Hesselink JM*
Department of Molecular Pharmacology, Pain Specialist, Faculty of Health, University of Witten, Germany
- *Corresponding Author:
- Keppel Hesselink JM
Department of Molecular Pharmacology, Pain Specialist
Faculty of Health, University of Witten/Herdecke, Germany
Tel: 06-51700527
E-mail: jan@neuropathie.nu
Received date: October 31, 2016; Accepted date: November 09, 2016; Published date: November 11, 2016
Citation: Hesselink JMK (2016) Topical Analgesics: Critical Issues Related to Formulation and Concentration. J Pain Relief 5:274. doi: 10.4172/2167-0846.1000274
Copyright: © 2016 Hesselink JMK, 2016. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abstract
Topical analgesics are in need to be differentiated from transdermal formulations of analgesics. Topical analgesics are characterized by local analgesic effects in the absence of systemic effects, and do not require a transdermal delivery formulation. There are two key issues in the development of topical analgesics. 1. For optimal clinical effects specific characteristics for the vehicle (a cream base or gel base) are required, depending on the physicochemical characteristics of the pharmaceutical active ingredient in the carrier. 2. One cannot and should not skip well designed phase II dose-finding studies, and this unfortunately happens often, as we will discuss in this paper. In fact, we will demonstrate underdosing is one of the major hurdles to detect meaningful and statistically relevant clinical effects of topical analgesics. In the case of gels or creams containing ketamine, amitriptyline and baclofen, the dose-finding most probably needs to start at 10% for ketamine and amitriptyline and 2.5% for baclofen, while the doses tested were much lower: 4%, 2% and 1% respectively. Topical analgesics are promising inroads for the treatment of neuropathic pain, once sufficient attention is given to aspects such as formulation and concentration.
