CYP2C19 metabolizer status (clopidogrel & others)

CYP2C19 activates the anti-clotting drug clopidogrel (Plavix) and clears several others, including some antidepressants, acid-reflux PPIs and the antifungal voriconazole. Two common variants set your speed: *2 switches the enzyme off and *17 speeds it up. Reading both together gives your overall metabolizer status, the way clinical dosing does, rather than judging one variant alone.

Possible results

Poor metabolizer. You have two non-working copies of CYP2C19 (*2/*2), so you're a poor metabolizer. You activate very little of the anti-clotting drug clopidogrel (Plavix), so it may protect you much less, and doctors often choose a different antiplatelet drug. The flip side is that some other CYP2C19-cleared drugs (certain antidepressants, acid-reflux PPIs) can build up to higher levels. Worth flagging if any of these are ever prescribed.

Intermediate metabolizer. You carry one non-working copy of CYP2C19 (*2), making you an intermediate metabolizer. You activate the anti-clotting drug clopidogrel less well than usual, so it may protect you a bit less and an alternative is sometimes considered. This mainly matters around clopidogrel and a few other CYP2C19 drugs.

Normal metabolizer. You carry the standard versions of CYP2C19 (no *2 or *17), so you're a normal metabolizer: you activate clopidogrel and clear the other CYP2C19 drugs at the usual rate, and standard dosing generally fits. A few rarer CYP2C19 variants are not tested here.

Rapid metabolizer. You carry one increased-function copy of CYP2C19 (*17), making you a rapid metabolizer. You activate the anti-clotting drug clopidogrel well, and you clear some other CYP2C19 drugs a little faster than average. This is mostly favorable for clopidogrel and only occasionally relevant for other medicines.

Ultrarapid metabolizer. You have two increased-function copies of CYP2C19 (*17/*17), making you an ultrarapid metabolizer. You activate clopidogrel very efficiently (fine, even helpful, for that drug), but you also clear some other CYP2C19 drugs quickly, so standard doses of certain acid-reflux PPIs, antidepressants or the antifungal voriconazole may run low. Worth knowing if those are prescribed.

Evidence & sources

This panel reads CYP2C19*2, CYP2C19*17.

Reads the two most common CYP2C19 variants: the loss-of-function *2 and the increased-function *17. Together they classify most people of European ancestry, but rarer no-function alleles (*3, common in East Asians, plus *4 to *8) are not tested, so a 'normal', 'rapid' or 'ultrarapid' result does not fully rule them out.

CPIC provides dosing guidance for clopidogrel based on this gene.

Related

Drug acetylation speed (NAT2) · Efavirenz / drug metabolism (CYP2B6*6) · Gilbert syndrome (UGT1A1 gene) · Hepatitis C treatment response (IL28B) · Statin-induced myopathy risk · Tacrolimus metabolism (CYP3A5 gene) · Thiopurine metabolism (TPMT and NUDT15 genes)