:Modafinil acid

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| ImageFile = Modafinil_acid.svg

| ImageSize = 200px

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| PIN = (Diphenylmethanesulfinyl)acetic acid

| OtherNames = Modafinilic acid; Modafinil carboxylate; CRL-40467

| Section1 = {{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 63547-24-0

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 54N37HN7N4

| PubChem = 3085267

| SMILES = C1=CC=C(C=C1)C(C2=CC=CC=C2)S(=O)CC(=O)O

| StdInChI = InChI=1S/C15H14O3S/c16-14(17)11-19(18)15(12-7-3-1-4-8-12)13-9-5-2-6-10-13/h1-10,15H,11H2,(H,16,17)

| StdInChIKey = QARQPIWTMBRJFX-UHFFFAOYSA-N

| ChemSpiderID = 2342211

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| Section2 = {{Chembox Properties

| C = 15 | H = 14 | O = 3 | S = 1

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| Section3 = {{Chembox Hazards

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Modafinil acid (code name CRL-40467), also known as modafinilic acid or modafinil carboxylate, is one of the two major metabolites of modafinil – the other being modafinil sulfone.{{cite journal | vauthors = Dubey S, Ahi S, Reddy IM, Kaur T, Beotra A, Jain S | title = A novel study of screening and confirmation of modafinil, adrafinil and their metabolite modafinilic acid under EI-GC-MS and ESI-LC-MS-MS ionization | journal = Indian Journal of Pharmacology | volume = 41 | issue = 6 | pages = 278–283 | date = December 2009 | pmid = 20407560 | pmc = 2846503 | doi = 10.4103/0253-7613.59928 | doi-access = free }} Modafinil acid is also a metabolite of the modafinil prodrug, adrafinil, and the (R)-(–)-enantiomer is a metabolite of armodafinil, the (R)-(–)-enantiomer of modafinil.{{cite journal | vauthors = Sousa A, Dinis-Oliveira RJ | title = Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects | journal = Substance Abuse | volume = 41 | issue = 2 | pages = 155–173 | date = 2020 | pmid = 31951804 | doi = 10.1080/08897077.2019.1700584 | s2cid = 210709160 }} Between 30 - 60% of modafinil is converted to modafinil acid and its half life is roughly half that of modafinil (about 7 hours).{{cite journal | vauthors = Wong YN, King SP, Simcoe D, Gorman S, Laughton W, McCormick GC, Grebow P | title = Open-label, single-dose pharmacokinetic study of modafinil tablets: influence of age and gender in normal subjects | journal = Journal of Clinical Pharmacology | volume = 39 | issue = 3 | pages = 281–288 | date = March 1999 | pmid = 10073328 | doi = 10.1177/009127009903900312 | s2cid = 30258993 }} Modafinil acid seems to be inactive,{{cite journal | vauthors = Wong YN, Wang L, Hartman L, Simcoe D, Chen Y, Laughton W, Eldon R, Markland C, Grebow P | display-authors = 6 | title = Comparison of the single-dose pharmacokinetics and tolerability of modafinil and dextroamphetamine administered alone or in combination in healthy male volunteers | journal = Journal of Clinical Pharmacology | volume = 38 | issue = 10 | pages = 971–978 | date = October 1998 | pmid = 9807980 | doi = 10.1002/j.1552-4604.1998.tb04395.x | s2cid = 32857213 }} and similarly to modafinil sulfone, does not appear to contribute to the wakefulness-promoting/psychostimulant effects of modafinil.{{cite journal | vauthors = Schwertner HA, Kong SB | title = Determination of modafinil in plasma and urine by reversed phase high-performance liquid-chromatography | journal = Journal of Pharmaceutical and Biomedical Analysis | volume = 37 | issue = 3 | pages = 475–479 | date = March 2005 | pmid = 15740906 | doi = 10.1016/j.jpba.2004.11.014 | url = https://zenodo.org/record/1259161 }}{{cite journal | vauthors = Robertson P, Hellriegel ET | title = Clinical pharmacokinetic profile of modafinil | journal = Clinical Pharmacokinetics | volume = 42 | issue = 2 | pages = 123–137 | year = 2003 | pmid = 12537513 | doi = 10.2165/00003088-200342020-00002 | s2cid = 1266677 }}{{cite journal | vauthors = Robertson P, Hellriegel ET, Arora S, Nelson M | title = Effect of modafinil on the pharmacokinetics of ethinyl estradiol and triazolam in healthy volunteers | journal = Clinical Pharmacology and Therapeutics | volume = 71 | issue = 1 | pages = 46–56 | date = January 2002 | pmid = 11823757 | doi = 10.1067/mcp.2002.121217 | s2cid = 21552865 }}

In the breakdown process of modafinil, modafinil is primarily hydrolyzed by an esterase or amidase enzyme into modafinil acid.{{cite journal | vauthors = Wu KH, Guo T, Deng CH, Guan Z, Li L, Zhou TY, Lu W | title = Population pharmacokinetics of modafinil acid and estimation of the metabolic conversion of modafinil into modafinil acid in 5 major ethnic groups of China | journal = Acta Pharmacologica Sinica | volume = 33 | issue = 11 | pages = 1401–1408 | date = November 2012 | pmid = 23103618 | pmc = 4011351 | doi = 10.1038/aps.2012.124 }} The apparent clearance of modafinil acid is significantly higher than that of modafinil, following the hypothesis that metabolism increases the polarity and the clearance of modafinil.{{Cite web|url=http://www.brainsupplements.co.uk/modafinil-physical-performance-enhancer/|title=Modafinil As A Physical Performance Enhancer|language=en-US|access-date=2017-02-22}}