Cumulative evidence of the low reliability of frozen/thawed pig skin as a model for in vitro percutaneous permeation testing. 2017

Amnon C Sintov
Department of Biomedical Engineering, Faculty of Engineering Sciences, Ben-Gurion University of the Negev, Be'er Sheva 84105, Israel. Electronic address: asintov@bgu.ac.il.

Porcine skin has frequently been used as a model in in vitro permeation studies being considered as an excellent alternative for human skin due to biochemical similarities. The use of frozen skin after thawing is particularly more convenient for these studies since it is available whenever needed. Even though several researchers have noticed that freezing and then thawing the tissue result in enhancement of drug permeation, many published articles have still described studies using frozen pig skin for bioequivalence and transdermal evaluation of drug products. The aim of this commentary article is therefore to explicitly demonstrate, according to our experience, the low-reliability of the convenient protocol of freezing pig skin for in vitro percutaneous studies. It has been shown in three separate studies using three different drugs that frozen/thawed pig skin had a higher permeability to drugs compared to that obtained by using fresh skin. The results have further demonstrated that the abnormal permeability through frozen pig skin is independent of the effect of different formulations, placing a question mark on the validity of the not freshly-used porcine skin for in vitro penetration studies.

UI MeSH Term Description Entries
D007980 Levodopa The naturally occurring form of DIHYDROXYPHENYLALANINE and the immediate precursor of DOPAMINE. Unlike dopamine itself, it can be taken orally and crosses the blood-brain barrier. It is rapidly taken up by dopaminergic neurons and converted to DOPAMINE. It is used for the treatment of PARKINSONIAN DISORDERS and is usually given with agents that inhibit its conversion to dopamine outside of the central nervous system. L-Dopa,3-Hydroxy-L-tyrosine,Dopaflex,Dopar,L-3,4-Dihydroxyphenylalanine,Larodopa,Levopa,3 Hydroxy L tyrosine,L 3,4 Dihydroxyphenylalanine,L Dopa
D010539 Permeability Property of membranes and other structures to permit passage of light, heat, gases, liquids, metabolites, and mineral ions. Permeabilities
D002110 Caffeine A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling. 1,3,7-Trimethylxanthine,Caffedrine,Coffeinum N,Coffeinum Purrum,Dexitac,Durvitan,No Doz,Percoffedrinol N,Percutaféine,Quick-Pep,Vivarin,Quick Pep,QuickPep
D004008 Diclofenac A non-steroidal anti-inflammatory agent (NSAID) with antipyretic and analgesic actions. It is primarily available as the sodium salt. Diclophenac,Dichlofenal,Diclofenac Potassium,Diclofenac Sodium,Diclonate P,Dicrofenac,Feloran,GP-45,840,Novapirina,Orthofen,Orthophen,Ortofen,SR-38,Sodium Diclofenac,Voltaren,Voltarol,Diclofenac, Sodium,GP 45,840,GP45,840,SR 38,SR38
D005615 Freezing Liquids transforming into solids by the removal of heat. Melting
D000279 Administration, Cutaneous The application of suitable drug dosage forms to the skin for either local or systemic effects. Cutaneous Drug Administration,Dermal Drug Administration,Drug Administration, Dermal,Percutaneous Administration,Skin Drug Administration,Transcutaneous Administration,Transdermal Administration,Administration, Dermal,Administration, Transcutaneous,Administration, Transdermal,Cutaneous Administration,Cutaneous Administration, Drug,Dermal Administration,Drug Administration, Cutaneous,Skin Administration, Drug,Administration, Cutaneous Drug,Administration, Dermal Drug,Administration, Percutaneous,Administrations, Cutaneous,Administrations, Cutaneous Drug,Administrations, Dermal,Administrations, Dermal Drug,Administrations, Percutaneous,Administrations, Transcutaneous,Administrations, Transdermal,Cutaneous Administrations,Cutaneous Administrations, Drug,Cutaneous Drug Administrations,Dermal Administrations,Dermal Drug Administrations,Drug Administrations, Cutaneous,Drug Administrations, Dermal,Drug Skin Administrations,Percutaneous Administrations,Skin Administrations, Drug,Skin Drug Administrations,Transcutaneous Administrations,Transdermal Administrations
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012867 Skin The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.
D012869 Skin Absorption Uptake of substances through the SKIN. Absorption, Skin,Intracutaneous Absorption,Intradermal Absorption,Percutaneous Absorption,Transcutaneous Absorption,Transdermal Absorption,Absorption, Intracutaneous,Absorption, Intradermal,Absorption, Percutaneous,Absorption, Transcutaneous,Absorption, Transdermal,Absorptions, Intracutaneous,Absorptions, Intradermal,Absorptions, Percutaneous,Absorptions, Skin,Absorptions, Transcutaneous,Absorptions, Transdermal,Intracutaneous Absorptions,Intradermal Absorptions,Percutaneous Absorptions,Skin Absorptions,Transcutaneous Absorptions,Transdermal Absorptions
D013552 Swine Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA). Phacochoerus,Pigs,Suidae,Warthogs,Wart Hogs,Hog, Wart,Hogs, Wart,Wart Hog

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