FROM OUR EXPERTS
EPIDERMIS
DERMIS
SUBCUTANEOUS TISSUE Skin is a barrier that exists to keep body water in and microorganisms and noxious chemicals out. The skin consists of three main layers: the epidermis, the dermis and the subcutaneous tissues. The epidermis actually has multiple layers, the most superficial of which is the stratum corneum, which provides almost all the skin’s protective properties. The stratum corneum is made up of keratin, which consists of dead skin cell remnants and fibrous proteins that overlap in layers. Transnormal absorption occurs via a passive diffusion through the epithelial cell layer, in a concentration-dependent process. The magnitude and speed of diffusion depends on the integrity and also physical properties of the applied drug. Drugs with low molecular weight with a high water and lipid solubility show the greatest penetration. Source: “Compounded Ointment Results in Severe Toxicity in a Pediatric Patient,” Pediatric Emergency Care, November 2013
Drugs you rub – continued from page 12 The toddler in this case was at particular risk because of his size and his rash. Any open wound on the skin can greatly increase absorption of anything applied to the skin. “The smaller the child is, the larger the surface area, relative to body weight ratio. As a human grows in volume, so does the surface area, but at a much slower rate,” the authors write. Adults have a small skin surface area-to-weight ratio, compared to infants, who have a large surface area in proportion to size and weight. “Because absorption depends on the amount of surface area exposed to a topical drug, a child will absorb a higher dose per kilogram than an adult.” The prescription in this case was a compound of several potent drugs known to cause central nervous system depression. Even a small amount was highly toxic to the little boy, who improved over the next 12 hours in intensive care and eventually recovered. ●
tAkeAwAy ●
Topical compounded preparations are increasingly prescribed for chronic pain.
●
These drugs are potent.
●
Many patients receive these customized prescriptions through the mail.
●
Childproof packaging is not standard.
●
Children are especially at risk for significant toxicity if they are exposed. Listen to an interview at upstate.edu/ healthlinkonair by searching “poison proof.”
Poison Center toxicologists Michael Holland, MD, Ross Sullivan, MD, and Jeanna Marraffa, PharmD
winter 2014
U P S TAT E H E A LT H
13