Herpes Zoster, better known as shingles can result in Postherpetic neuralgia (PHN) following reactivation of the varicella-zoster virus. This may produce chronic neuropathic pain similar to the PHN pain without the presence of a rash. PHN associated herpes zoster pain may be perceived as constant or intermittent burning, aching, or throbbing that occurs with or without stimulus; a majority of patients with PHN (~70%) develop allodynia (i.e. pain over the affected area when there is light touch).
Herpes Zoster Therapy options
A key issue with the treatment of HZ is that no disease modifying therapy exists. Early analgesics and interventions can prevent the persistence of pain. Dr. Dominic Hegarty (Clinical Director Pain Relief Ireland) acknowledges that GP’s are acutely aware of the issue and because they now prescribe analgesics and treatment early. Many individuals can control the pain and a good prognosis can be ensured.
The topical application of a 5% lidocaine patch is one treatment that can offer real pain management. This has emerged as a widely used treatment modality; however, as any individual who has used this system will tell you there are difficulties with patch adhesion and a resultant reduction in the patient treatment compliance have been reported. A recent survey revealed that 85% of patients have an issue with keeping the patch on a painful area. Detachment was reported at least once during the 12-hour treatment.
Of the 1,936 total cases reported to the FDA’s adverse event Reporting System as of March 2018, 1,347 (69.6%) were related to poor adhesion. The adhesive performance of topical patches is a critical factor that may determine drug delivery and patient compliance.
Forty-six percent of respondents said they used tape to help keep the patches in place over the area of pain or attached to the skin. In addition, 51% said their patch became detached or moved off the application area at least 3 times during the treatment period. Because of these issues, 49% switched patch brands at least once and 16% stopped using the patch altogether. Dr. Hegarty makes the point that having the patch in contact with the skin for 12 hours is very important to ensure that the maximise transfer of the lidocaine can be achieved. This is because the peak concentration is achieved at the 12 hour window.
To address these issues, Ztlido, a novel 1.8% lidocaine topical system, has been developed by Scilex Pharmaceuticals. Ztlido uses a proprietary, single-layered polymer matrix system that is bioequivalent to the 5% lidocaine patch to provide equivalent drug delivery in the treatment of PHN pain.
This product has yet to arrive on the Irish market but the evidence to date suggests that it has many of the same positive features of the traditional produce and address the adhesion issue. For example
- Like the 5% Lidocaine patch Ztlido has the same clinical indication and needs to be applied for 12 hours and both products reach the peak concentration at 12 hours.
- Due to the difference in the way the agent is managed there is less product in each patch and it provides the same level of treatment, (Ztlido (1.8%) has 36mgs of lidocaine v Lidocaine (5%) which has 700mgs)
- Ztlido is 7 times lighter and 50% thinner than the traditional lidocaine patch
- Ztlido has shown to stay attached to the affected area more often than the traditional patch: proven to maintain greater than 90% adhesion in more than 90% of patients at the end of the prescribed 12-hour administration period.
With its improved adhesion, Ztlido is an important addition to the PHN pain management armamentarium and can be utilized in a variety of patient types. For active patients, Ztlido is the only lidocaine patch proven to maintain adhesion during moderate exercise (tested after biking for 30 minutes). Like other topical analgesics, Ztlido carries a low risk for systemic adverse effects.
“It is positive that the pharma industry is recognising the practical issues and are providing real patient centred improvements with simple solutions”.
For the moment Dr. Hegarty says we will have to continue to make individuals aware of the issues surrounding patch displacement. What is important is that we have a long-term produce that can provide the sympathetic pain relief. “It is positive that the pharma industry is recognising the practical issues and are providing real patient centred improvements with simple solutions”.
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Ztlido (lidocaine topical system) 1.8% |LS|prescribing information|RS|. San diego, ca: SciLeX Pharmaceuticals, inc; november 2018.
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Pergolizzi JV. Pain Medicine News Oct 2019