Table III. Pharmacogenetic variants associated with antipsychotic-induced side effects. SNP, single-nucleotide polymorphism; DRD, dopamine receptor; HTR, serotonin receptor; MCR, melanocortin receptor; HLA, human leukocyte antigen; HSPG, heparan sulfate proteoglycan. ^aResults are based on allelic model;^bResults are based on additive genotypic model.

Gene	SNP	Risk allele	Outcome measure	OR (95% CI; P)	Functional effect
Weight gain
HTR2C	C-759T (rs3813929)	C	Gaining ≥7 % baseline weight	Chronic samples 1.64a (0.73-3.69; 0.23)53, First episode sample 5.40a (2.08-14.01; 0.001)53	Affects transcription factor binding to HTR2C promoter,85 unclear if C allele increases86 or decreases87,88 HTR2C expression
MC4R	rs489693	A	Weight gain (kg) from baseline	AA homozygotes gained ~ 3 kg mor weight than other genotypes11,56	Unknown
Agranulocytosis
HLA-DQB1	G6672C (rs113332494)	G	Absolute neutrophil count <500 cells/mm3 and discontinuation of clozapine therapy	16.9 (3.57-109; <0.0001)60	Unknown
Tardive dyskinesia
CYP2D6	Poor and intermediate metabolizers	At least one *3, *4, *5, *6, or *10 allele	Presence of tardive dyskinesia	Prospective studies 1.83 (1.09-3.08; 0.02)63	Decreased CYP2D6 enzyme activity89
DRD2	Taq 1A (rs1800497)	C, A2	Presence of tardive dyskinesia	1.30b (1.09-1.55; 0.003)64	Increased DRD2 receptor availability90,91
HTR2A	T102C (rs6313)	C	Presence of tardive dyskinesia	1.64b (1.17-2.32; 0.004)65	Decreased HTR2A expression,92 decreased HTR2A reception binding93
HSPG2	rs2445142	G	Presence of tardive dyskinesia	2.09a (1.07-4.06; 0.03)67	Increased HSPG2 expression66