Table 1.

Examples of pharmacogenetic susceptibility for drug-specific adverse drug reactions.

Drug/drug class	Pharmacogenetic marker	Additional susceptibility factors	Example of clinical context
Carbamazepine	HLA B*15:02 (in the populations listed)	Han-Chinese, Thai and Malaysian populations	Marker for carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis
Simvastatin	SLCO1B1 (solute carrier organic anion transporter 1B1)	Advanced age, untreated hypothyroidism, excess physical activity, concomitant medications (eg fibrates)	Statin-induced rhabdomyolysis (rare) whose risk is four times greater with single defective allele, 16 times greater with two defective alleles
Abacavir	HLA-B*57:01	Higher CD8 cell count at start of therapy	Marker for abacavir-induced hypersensitivity reactions with fever, rash, lethargy and abdominal and acute respiratory symptoms
Thiopurines (Azathioprine and mercaptopurine)	TPMT activity	N/A	1 in 10 individuals are heterozygous (50% normal TPMT activity) and 1 in 300 have completely deficient activity. Thiopurine-induced myelosuppression is associated with TPMT activity.

N/A = not applicable; TPMT = thiopurine methyl transferase