Transdermal absorption

Industrial environments expose individuals to a plethora of airborne chemical compounds in the form of vapors, aerosols, or biphasic mixtures of both. These atmospheric contaminants primarily interface with two body surfaces the respiratory tract and the skin. Between these two routes of systemic exposure to airborne chemicals (inhalation and transdermal absorption) the respiratory tract has the larger surface area and a much greater percentage of this surface exposed to the ambient environment. Or dinary work clothing generally restricts skin exposures to the arms, neck, and head, and special protective clothing ensembles further limit or totally eliminate skin exposures, but breathing exposes much of the airway to contaminants. 

Blodinger, J. (1982). Formulation of Veterinary Dosage Forms. Marcel Dekker, New York. Borowitz, J.L., Moore, P.F., Yim, G.K.W. and Miya, T.S. (1971). Mechanism of enhanced drug effects produced by dilution of the oral dose. Toxicol. Appl. Pharmacol. 19 164-168. Brandau, R. and Lippold, B.H. (1982). Dermal and Transdermal Absorption. Wissenschaf-tliche, Verlagsgesellschaft mbH, Stuttgart. 

Ziegenmeyer, J. (1982). The influence of the vehicle on the absorption and permeation of drugs. In Dermal and Transdermal Absorption (Brandan, R. and Reisen, R, Eds.). Wissenschaf-tliche, Verlagsgesellschaft, Stuttgart, pp. 73-89. 

S. M. Wagner, A. C. Nogueira, M. Paul, D. Heydeck, S. Klug, and B. Christ. The isolated normothermic hemoperfused porcine forelimb as a test system for transdermal absorption studies. J. Artif. Organs 6 183-191 (2003). 

Pharmacokinetics The transdermal absorption of tretinoin from various topical formulations ranged from 1 % to 31 % of applied dose, depending on whether it was applied to healthy skin or dermatitic skin. 

Phenelzine Blockade of MAO-A and MAO-B (phenelzine, nonselective) MAO-B irreversible selective MAO-B inhibition (low dose selegiline) Transdermal absorption of selegiline achieves levels that inhibit MAO-A Major depression unresponsive to other drugs Very slow elimination Toxicity Hypotension, insomnia Interactions Hypertensive crisis with tyramine, other indirect sympathomimetics serotonin syndrome with serotonergic agents, meperidine... 

Klose, K.T., Humberstone, A.J., Finnin, B.C. Comparative transdermal absorption of fentanyl after application of a spray and Duragesic patch. PPP Transdermal Conference, April 2002. 

Topical application of testosterone, as a gel or from transdermal patches, can lead to absorption and systemic effects (SEDA-16, 158). Transdermal absorption of testosterone (usually from treatment of vulvar lichen scler-osus et atrophicus) can lead to increased libido, clitoral hypertrophy, pubic hirsutism, thinning of the scalp hair, facial acne, voice change, hirsutism, and even virilization (111). 

Transdermal absorption of estrogen can lead to pseudo-precocious puberty in young girls, and to symptoms in young boys and adult men such as gynecomastia, loss of libido, impotence, and galactorrhea (229-231). 

Dkeidek, I., and E. Touitou. 1999. Transdermal absorption of polypeptides. AAPS Pharm Sci 1 S202. 

Advanced delivery systems include transdermal patches, which are now well established and accepted by patients. Technologies under development include, for example, iontophoresis, which uses a small electric current to propel the drag through the skin. Drag delivery via iontophoresis occurs at enhanced rates and amounts in comparison to patch technology, which uses simple passive diffusion. The development of safe, non-toxic absorption enhancers to facilitate transdermal absorption is a further focus of current research. 

Aluminum enters the human organism via the gastrointestinal (water, beverages, drugs, cosmetics, foods) or respiratory apparatus (inhaled dust), by intranasal absorption to the brain, and by transdermal absorption [15]. Most of the metal is excluded by intervention of the gastrointestinal barrier and by renal function. Also, some accumulation occurs in the entire body, including brain, heart muscle, bones, and lungs (Fig. 1). 

Injections into the subcutaneous or intradermal sites do not require that the animals are anesthetized however, intradermal injections are significantly easier when the animals are unconscious or sedated. Metastatic potential does not seem to be affected by anesthetics at this step. Methoxyllurane (Metofane , Pitman-Moore) inhalation anesthetic is relatively inexpensive and effective for this purpose. A homemade anesthesia jar will suffice. Place a small volume of Metofane under a wire screen suspended above the floor of a container with a lid. Mice and rats will be unconscious within 3-5 min and the effects will last less than 5 min. It is crucial that the animals never come into contact with the fluid. Transdermal absorption can be lethal. Also, anyone using this inhalant should also be cognisant of the content within the Material Safety Data Sheets (MSDS) and the chances of pathologies if overexposed. Hint construct the anesthesia jar with a wire mesh that allows feces to drop as this maintains clean conditions. This provides for easier and more complete cleaning of the jar. 

Explosives factory workers exposed to a nitrate-contaminated environment lost it over a weekend and some chose to maintain their intake by using nitrate impregnated headbands (transdermal absorption) rather than have to accept the headaches and reacquire tolerance so frequently. 

On the other hand, highly lipophilic compounds, such as hormones, can be solubilized via the prodrug approach. For example, the rate of transdermal absorption of the highly lipophilic drug, testosterone, was enhanced over 50-fold by forming water-soluble, yet lipophilic, prodrug ester.f The prodrug testoster-onyl-4-dimethylaminobutyrate was found to penetrate human skin tissue, in vitro, 54 times faster than... 

Karim, A. Transdermal absorption a unique opportunity for constant delivery of nitroglycerin. Drug Develop. Ind. Pharm. 1983, 9, 671. 

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