The standard starting dose was calibrated on people whose CYP3A5 does not work, because in Europe that is most people. The ones whose enzyme is intact get too little — in the first days after a transplant, when too little means rejection.
Tacrolimus prevents rejection of a transplanted organ and has a narrow therapeutic window. CYP3A5 expressers — anybody with at least one functional copy — clear it faster and reach a lower blood level on the same dose. CPIC recommends starting an expresser at about 1.5 to 2 times the standard dose, with the usual therapeutic drug monitoring continuing unchanged, rather than arriving at the right dose through several days of subtherapeutic readings. The target concentration itself does not change. Because functional copies are much more common in people of African ancestry, a single standard starting dose under-treats that group in the days when rejection is the risk. Dosing here is a transplant team’s decision, measured directly in blood, and is not something to act on from a raw data file.
Every guideline above was written by people. Named here because they are contributors to this page in the same sense anybody else on this site is.
These are the positions in your own file that carry the genes above. Not every gene in a guideline is one we report — where that is the case the gene appears above without a variant here, and the note says so.
CYP3A5 · rs188845491
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