When we think of bioavailability, we often imagine oral medications or injectables. But in dermatology, topical bioavailability, how much of a substance is available to act at the target site within or on the skin, is a game-changer. Despite being locally applied, topicals can be incredibly sophisticated in their delivery and action.
What Is Bioavailability in the Context of Skin?
In pharmacology, bioavailability generally refers to the fraction of an administered dose that reaches systemic circulation. But for topical or dermal applications, it’s about how effectively the active ingredient reaches its intended layer, whether that’s the epidermis, dermis, or deeper.
Unlike oral drugs, which must survive stomach acid and liver metabolism, topical products face a different kind of barrier: the stratum corneum, the skin’s natural defense.
Why Bioavailability Is Harder for Topicals
The stratum corneum consists of keratinized dead cells embedded in lipids, making it an excellent barrier to keep things out. Only molecules under 500 Daltons, with optimal lipophilicity, can pass through efficiently. That’s why not all actives are created equal and why formulation science is so important.
How Formulation Influences Bioavailability
Formulation is the unsung hero in topical science. Factors that impact bioavailability include:
- Particle size: Smaller particles penetrate better. Nanocarriers like cetosomes enhance delivery.
- Vehicle type: Creams, gels, ointments, and sprays affect absorption differently.
- pH and solubility: Compatibility with the skin’s pH helps prevent irritation and promotes uptake.
- Penetration enhancers: These include ethanol, surfactants, or essential oils that transiently disrupt the stratum corneum.
Systemic vs Local Availability
Topical bioavailability is not just about systemic absorption. In many cases, like Cymbiotics’ work, the goal is localized delivery with minimal systemic exposure. This is crucial in dermatology, where treatments often need to act precisely on inflamed or damaged skin regions without disturbing the entire body.
How Cymbiotics Leverages This
Cymbiotics’ innovation lies in enhancing dermal bioavailability using technologies like Cetosomes™ and FADD (Fast Acting Dermal Delivery). These systems are engineered to:
- Optimize particle size for skin penetration
- Use polarity-matched solvents and surfactants
- Improve stability of sensitive ingredients
- Deliver actives deeper without systemic overload
These are not mere emulsions, they are bioengineered platforms designed for maximum efficacy.
Bottom Line
Bioavailability in topicals isn’t about reaching the bloodstream, it’s about reaching the right place in the skin at the right dose. Understanding this helps us build better products, especially when formulation science is aligned with skin biology. At Cymbiotics, this principle drives every innovation.
References
- “The 500 Dalton rule for skin penetration” – Bos JD, Meinardi MM, Experimental Dermatology, 2000.
- “Transdermal drug delivery: penetration enhancement techniques” – Benson HAE, Current Drug Delivery, 2005.
- “Particle size of liposomes influences dermal delivery of substances” – Verma DD et al., European Journal of Pharmaceutics and Biopharmaceutics, 2003.
- “Design principles of chemical penetration enhancers for transdermal drug delivery” – Karande P et al., Proceedings of the National Academy of Sciences, 2005.
- “Transdermal drug delivery” – Prausnitz MR, Langer R, Nature Biotechnology, 2008.