Drug Interactions

Capsaicin increases the time blood needs to clot, and when taken with anticoagulant medicines like warfarin, the effect of the medicine may be intensified.


Acute oral LD50 values were determined to be 97.4 mg/kg and 118.8 mg/kg in female and male mice, respectively, and 148.1 mg/kg and 161.2 mg/kg in female and male rats, respectively.[1]


CYP2C9 was identified as the primary enzyme responsible for converting capsaicin into 16-hydroxy-capsaicin and 16,17-dehydro-capsaicin. CYP2C19 may also contribute to the formation of 16-hydroxy-capsaicin.[4]

Effects On Cytochrome P450 Enzymes

Effects in Humans In Vivo

None have been reported.

Effects in Rats In Vivo

Capsaicin was found to induce CYP3A4 in rats.[2]

In rats multiple doses of capsaicin and dihydrocapsaicin also induced CYP2E1.[3]

Effects In Vitro

The tests discussed in this section are in vitro tests. It's important to note that in many cases these kinds of enzyme based tests show different results from those seen in real human test subjects.

At concentrations occurring after ingestion of chili peppers or topical administration of a high-concentration patch, capsaicin did not cause any direct inhibition of any Cytochrome P450 enzymes. Inhibition was only observed at much higher concentrations.[5]

An in vitro test performed on human liver microsomes found that capsaicin and dihydrocapsaicin moderately inhibited the Cytochrome P450 enzymes CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4 and CYP3A5. IC50 values ranged from 4.4 to 61.8 μM.[3]

Another vitro test showed that capsaicin inhibited CYP1A2, CYP2C9 and CYP2C19, with IC50 values of 2.1, 2.0 and 3.2 mcM, respectively. Capsaicin also appeared to inhibit CYP2B6, CYP2D6, CYP3A4 and CYP3A4 directly with IC50 values of 24, 18, 38 and 12 mcM, respectively. The same test showed that capsaicin did not induce CYP1A2, CYP2C9, CYP2C19, CYP2B6, CYP2D6, CYP3A4 or CYP3A4.[4]

Another in vitro test found that capsaicin did not induce CYP2E1 but instead induced CYP1A2 by 8.6%.[5]

1. Saito, A.; Yamamoto;
M. Acute Oral Toxicity of Capsaicin in Mice and Rats; J. Toxicol. Sci. 1996, 21, 195-200.
2. Mol Nutr Food Res. 2012 May;56(5):797-809. doi: 10.1002/mnfr.201100697.
Capsaicin induces CYP3A4 expression via pregnane X receptor and CCAAT/enhancer-binding protein β activation. Han EH, Kim HG, Choi JH, Jang YJ, Lee SS, Kwon KI, Kim E, Noh K, Jeong TC, Hwang YP, Chung YC, Kang W, Jeong HG; Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon, Republic of Korea. PubMed PMID: 22648626
3. J Asian Nat Prod Res. 2012;14(4):382-95. doi: 10.1080/10286020.2012.656605.
Effects of capsaicin and dihydrocapsaicin on human and rat liver microsomal CYP450 enzyme activities in vitro and in vivo. Zhang QH, Hu JP, Wang BL, Li Y. Chinese Academy of Medical Sciences & Peking Union Medical College, Institute of Materia Medica, Beijing 100050, China; PubMed PMID: 22375877
International Nonproprietary Name: capsaicin; Procedure No. EMEA/H/C/000909; 7 Westferry Circus, Canary Wharf, London, E14 4HB, UK; European Medicines Agency; Evaluation of Medicines for Human Use; © European Medicines Agency, 2009; Doc.Ref.: EMEA/CHMP/95213/2009 (Download Attached PDF Document)
5. Inhibition and induction of human cytochrome P450 enzymes in vitro by capsaicin
Babbar, Sunita; Chanda, Sanjay; Bley, Keith; Xenobiotica , Volume 40 (12); Informa Healthcare – Dec 1, 2010; Copyright© 2010 Informa UK, Ltd.; General Xenobiochemistry; ISSN 0049-8254; eISSN 1366-5928; D.O.I. 10.3109/00498254.2010.520044;
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