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Clinical data
Synonyms 4-Hydroxyanisole; para-Guaiacol
AHFS/ International Drug Names
MedlinePlus a682437
Routes of
ATC code
Legal status
Legal status
  • CA: Unscheduled
  • US: ℞-only and Unscheduled
  • In general: unscheduled
CAS Number
PubChem CID
ECHA InfoCard 100.005.246
Chemical and physical data
Formula C7H8O2
Molar mass 124.13722 g/mol
Density 1.55 g/cm3
Melting point 52.5 °C (126.5 °F)
Boiling point 243 °C (469 °F)

Mequinol, MEHQ or 4-Methoxyphenol, is a phenol used in dermatology[1] and organic chemistry.[2]



Mequinol is a common active ingredient in topical drugs used for skin depigmentation. As a topical drug Mequinol is often mixed with tretinoin, a topical retinoid. A common formulation for this drug is an ethanolic solution of 2% Mequinol and 0.01% tretinoin by mass.[1] Dermatologists commonly prescribe the drug to treat solar lentigines, liver spots, or age spots.

Lower dosages of mequinol have been used in conjunction with a Q-switched laser to depigment skin in patients with disseminated idiopathic vitiligo.[3]

Organic chemistry[edit]

In organic chemistry 4-methoxyphenol is used to inhibit the radical polymerization of monomers (e.g. acrylates or styrene monomers).[2]


4-Methoxyphenol is produced from p-benzoquinone and methanol via a free radical reaction.[4][5]


People can be exposed to 4-methoxyphenol in the workplace by breathing it in, skin absorption, swallowing it, skin contact, and eye contact. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 5 mg/m3 over an 8-hour workday.[6]

See also[edit]


  1. ^ a b Stiefel Laboratories, Inc. "Full Prescribing Information" (PDF). US Food and Drug Admistration. Retrieved 2 January 2015. 
  2. ^ a b Hudnall, Phillip M. (2000). "Hydroquinone". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a13_499. 
  3. ^ Komen, L.; Zwertbroek, L.; Burger, S.J.; van der Veen, J.P.W.; de Rie, M.A.; Wolkerstorfer, A. (2013). "Q-switched laser depigmentation in vitiligo, most effective in active disease". British Journal of Dermatology. 169 (6): 1246–1251. doi:10.1111/bjd.12571. 
  4. ^ Cristian, Gambarotti; Lucio, Melone; Carlo, Punta; Suresh Udhavrao, Shisodia (2013). "Selective Monoetherification of 1,4-Hydroquinone Promoted by NaNO2". Current Organic Chemistry. 17 (10): 1108–1113. 
  5. ^ Correale, Mariano; Panseri, Pietro; Romano, Ugo; Minisci, Francesco. "Process for the preparation of mono-ethers of hydroquinones US4933504A". Google Patents. Enichem Synthesis S.P.A. Retrieved 2 January 2015. 
  6. ^ "CDC - NIOSH Pocket Guide to Chemical Hazards - 4-Methoxyphenol". Retrieved 2015-11-20.