What Makes a Once Weekly Topical Possible
Topical treatments applied just once a week sound like a dream for busy people dealing with skin or hair issues. They work because of smart science that lets the medicine stay active in your skin for days after one application. This happens through special ingredients and designs that help the drug sink deep into the skin and release slowly over time.
Skin acts like a tough wall to keep things out. The outer layer, called the stratum corneum, blocks most drugs from getting through. It has dead skin cells packed tight in a mix of fats and proteins. Drugs can try to slip through the spaces between cells, directly through the cells themselves, or via tiny paths like hair follicles and sweat glands. Without help, most topicals wash off or sit on the surface and lose power fast.
To make once weekly dosing real, formulators add penetration enhancers. These are chemicals like ethanol or dimethyl sulfoxide that loosen up the skin barrier. They make the fats between cells more fluid so the drug can pass easier. Others, like tretinoin, speed up skin cell turnover. This creates tiny channels by breaking down the glue holding dead cells together, letting more drug in.[1][2]
Hair follicles offer a bonus path. They act like shortcuts straight to where hair grows or where pain signals start. In hair loss treatments, drugs target these follicles to build up inside and create a reservoir. The medicine sticks around, releasing bit by bit to keep levels steady for a week or more. Studies show topical finasteride with enhancers cuts scalp DHT, a hormone linked to hair thinning, by 68 to 75 percent. This matches pills but with less effect on the whole body.[1]
Carriers take it further. Liposomes and nanoemulsions wrap the drug in tiny bubbles that merge with skin lipids. Polymeric gels control how fast the drug comes out, keeping it active without daily reapplication. These setups reduce irritation and boost how long the treatment lasts right where needed.[2]
Real world examples prove it works. Roflumilast foam, a once daily option that could inspire weekly versions, hits skin inflammation fast without steroids. It uses PDE4 inhibition to calm plaques in psoriasis. Other topicals like diclofenac gel for pain deliver drugs to sore spots with low blood levels, cutting side effects.[2][6]
Keratolytics like alpha hydroxy acids or urea soften thick skin buildup, helping drugs reach deeper. They break corneocyte bonds to smooth the way for active ingredients.[5] Together, these tricks turn frequent applications into rare ones, making treatment simpler and more effective.
Sources
https://hairgp.co.uk/topical-finasteride-enhancers-better-hair-loss-results/
https://www.nysora.com/education-news/topical-analgesics-in-pain-management-pharmacologic-insights-and-clinical-impact/
https://www.droracle.ai/articles/630423/what-are-the-guidelines-for-using-topical-treatments-for
https://www.ncbi.nlm.nih.gov/books/NBK441898/
https://www.cureus.com/articles/451397-the-effectiveness-of-topical-keratolytics-alpha-hydroxy-acidsbeta-hydroxy-acidsurea-in-treating-keratosis-pilaris-a-review-of-the-literature
https://www.dermatologytimes.com/view/dermatology-times-2025-year-in-review-drug-approvals
