Quality by Design-Based Development of a Herbal Ointment for Diabetic Neuropathic Pain: A Critical Review

Painful diabetic peripheral neuropathy affects a large share of people with long-standing diabetes, and the oral drugs used to treat it help only some patients while often causing dizziness, sedation and other adverse effects. Topical therapy, which keeps the drug near the painful skin and limits systemic exposure, is therefore an attractive option. Herbal ointments have a long traditional use for limb pain and numbness, yet they rarely reach clinical practice because their quality varies from batch to batch and their performance is seldom defined by measurable targets. Quality by Design (QbD), set out in ICH Q8(R2), Q9 and Q10, offers a way to build reproducibility into a product from the first day of development. This review brings together the pathophysiology of diabetic neuropathic pain, the clinical evidence for topical and herbal treatments, and published QbD work on semisolid and plant-based topical products. On that basis it lays out a practical roadmap for an herbal ointment: target product profile, critical quality attributes, risk ranking, a Box-Behnken optimization, design space, control strategy and analytical QbD. The review also points out where the evidence is thin, notably the absence of controlled clinical data for most plant extracts, and suggests what future studies need to show