Drug permeability

{{Short description|Measure of drug take up into the body}}

{{also|Theories of general anaesthetic action|Passive transport}}

In medicinal chemistry, Drug Permeability is an empirical parameter that indicates how quickly a chemical entity or an active pharmaceutical ingredient crosses a biological membrane or another biological barrier to become bioavailable in the body. Drug permeability, together with drug aqueous solubility are the two parameters that define the fate of the active ingredient after oral administration and ultimately define its bioavailability.{{Cite journal |last1=Amidon |first1=G. L. |last2=Lennernäs |first2=H. |last3=Shah |first3=V. P. |last4=Crison |first4=J. R. |date=March 1995 |title=A theoretical basis for a biopharmaceutic drug classification: the correlation of in vitro drug product dissolution and in vivo bioavailability |url=https://pubmed.ncbi.nlm.nih.gov/7617530/ |journal=Pharmaceutical Research |volume=12 |issue=3 |pages=413–420 |doi=10.1023/a:1016212804288 |issn=0724-8741 |pmid=7617530|hdl=2027.42/41443 |s2cid=21085622 |hdl-access=free }} When drug permeability is empirically measured in vitro, it is generally called apparent permeability (P_app) as its absolute value varies according to the method selected for its measurement. P_app is measured in vitro utilizing cellular based barriers such as the Caco-2{{Cite journal |last1=Artursson |first1=P. |last2=Karlsson |first2=J. |date=1991-03-29 |title=Correlation between oral drug absorption in humans and apparent drug permeability coefficients in human intestinal epithelial (Caco-2) cells |url=https://pubmed.ncbi.nlm.nih.gov/1673839/ |journal=Biochemical and Biophysical Research Communications |volume=175 |issue=3 |pages=880–885 |doi=10.1016/0006-291x(91)91647-u |issn=0006-291X |pmid=1673839}} model or utilizing artificial biomimetic barriers, such as the Parallel Artificial Membrane Permeation Assay (PAMPA){{Cite journal |last1=Kansy |first1=M. |last2=Senner |first2=F. |last3=Gubernator |first3=K. |date=1998-03-26 |title=Physicochemical high throughput screening: parallel artificial membrane permeation assay in the description of passive absorption processes |url=https://pubmed.ncbi.nlm.nih.gov/9544199/ |journal=Journal of Medicinal Chemistry |volume=41 |issue=7 |pages=1007–1010 |doi=10.1021/jm970530e |issn=0022-2623 |pmid=9544199}} or the PermeaPad.{{Cite journal |last1=di Cagno |first1=Massimiliano |last2=Bibi |first2=Hanady A. |last3=Bauer-Brandl |first3=Annette |date=2015-06-20 |title=New biomimetic barrier Permeapad™ for efficient investigation of passive permeability of drugs |url=https://pubmed.ncbi.nlm.nih.gov/25840123/ |journal=European Journal of Pharmaceutical Sciences|volume=73 |pages=29–34 |doi=10.1016/j.ejps.2015.03.019 |issn=1879-0720 |pmid=25840123}} All these methods are built on an acceptor compartment (from 0.2 up to several mL according to the method uses) where the drug solution is placed, a biomimetic barrier and an acceptor compartment, where the drug concentration is quantified over time. By maintaining sink condition, a steady state is reached after a lag time (τ, Fig. 1) .