Pain affects everyone at some time in their life, be it chronic arthritis or a one-off injury. Whilst the level of pain can vary hugely, even a small amount can significantly impact a person’s quality of life if it persists, so effective pain management is vitally important. The go to solution for many is an over-the-counter, systemic pain killer such as paracetamol or ibuprofen. However, pain is often localised to one area of the body, so why do we automatically resort to systemic treatments?
The most common drug class for pain treatment is nonsteroidal anti-inflammatory drugs (NSAIDs) which includes aspirin, ibuprofen and naproxen. Whilst effective in reducing pain, like any drug they are accompanied by the possibility of some problematic side effects: increased risk of gastrointestinal ulcers and bleeds, heart attack and kidney disease to name a few.1 Minimising these side effects is a key challenge in treating pain effectively; one possible solution is localised pain relief.
Targeted, localised treatment of pain is far from a recent innovation. Temperature based treatments have been widely used for many years, both in the form of direct heat or ice applied to the injury, and by way of heating/cooling creams, gels and sprays. Heat causes capillaries to dilate, allowing more blood to reach the damaged area, which speeds up healing. For pain caused by muscles in spasm, heat can also help the muscle to relax. Contrastingly, and often used in conjunction with heat, ice reduces inflammation and can numb the area, reducing pain.2
As with other localised pain relief therapies, the delivery of NSAIDs directly to the source of the pain via the skin has many benefits. A higher percentage of the active ingredient reaches the target site thereby resulting in lower systemic levels of the drug, significantly reducing the risk of many common side effects. Moreover, by applying pain relief locally rather than orally, the gastrointestinal tract is avoided entirely, further reducing the risk of potential side effects.
Topical application of pain relief via a patch overcomes several problems associated with other means of topical drug delivery, such as gels, creams and ointments. These generally must be applied multiple times a day, can rub off on clothing and, importantly, dose control is difficult. A patch, however, can potentially deliver the drug steadily over 24 hours from one application and, assuming it sticks well to the skin, there is certainty over the dose.
One challenge that must be overcome to enable effective local pain relief from topical application of a drug is the physical barrier of the skin. The properties of the skin which so effectively prevent water escaping the body also make it hard for other substances to cross the skin. Drugs chosen for this method of delivery must therefore be able to permeate the skin, usually assessed by whether they satisfy Lipinski’s rule of 5: have a molecular weight of <500 Da, <5 hydrogen bond donors, <10 hydrogen bond acceptors and a partition coefficient (log P, lipophilicity measurement) of <5.3 Not all drugs therefore are viable for topical delivery, however ibuprofen falls within these criteria, making it an ideal candidate for pain relief via the topical route.4
Medherant has produced an ibuprofen transdermal patch using its TEPI Patch® technology. Using a novel adhesive to dissolve the drug and any excipients, the TEPI Patch enables a higher payload so sufficient ibuprofen can be included to deliver the drug to local tissues for 24 hours. It also provides better adhesion, even in moist conditions. Medherant’s Ibuprofen TEPI Patch has been shown to be well tolerated in a clinical study of skin irritation and sensitisation. A second trial showed blood levels of ibuprofen were significantly lower following repeated application of the patch compared to a single oral dose, indicating that the drug is in the local tissues. Read more about the Ibuprofen TEPI Patch here or contact us to find out more about TEPI Patch technology.
Lipinski CA, Lombardo F, Dominy BW, et al. Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings. Adv Drug Deliv Rev. 2001;46(1–3):3–26. doi: 10.1016/S0169-409X(00)00129-0