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Test ID: HTR2O Serotonin Receptor Genotype (HTR2A and HTR2C), Saliva

Reporting Name

Serotonin Receptor 2A/2C, Saliva

Useful For

Guiding treatment choice of a (selective serotonin reuptake inhibitor) SSRI or non-SSRI antidepressant


Guiding treatment choice in individuals who have a drug-metabolizer phenotype discordant with CYP450 genotypes


Identifying patients who may benefit from treatment with the antipsychotic drug clozapine and aripiprazole


Identifying those patients at risk of excessive weight gain when receiving antipsychotic medications


Genotyping patients who prefer not to have venipuncture done

Specimen Type


Specimen Required

Multiple saliva genotype tests can be performed on a single specimen after a single extraction. See Multiple Saliva Genotype Tests in Special Instructions for a list of tests that can be ordered together.


Supplies: DNA Saliva Collection Kit (T651)

Container/Tube: Oragene DNA Self-Collection Kit (T651: fees apply)

Specimen Volume: Full tube

Collection Instructions:

1. Fill tube to line.

2. Send specimen in original container per kit instructions.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Saliva Ambient

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Wednesday; 8 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81479-Unlisted molecular pathology procedure

LOINC Code Information

Result ID Test Result Name Result LOINC Value
32936 HTR2A -1438G>A 75726-0
32937 HTR2A 74C>A 75728-6
32938 HTR2A 102 T>C 75731-0
32939 HTR2A IVS2 A>G 75727-8
32940 HTR2A 1354 C>T 75729-4
32941 HTR2C -759 C>T 75732-8
32942 HTR2C 796 G>C 75730-2
32943 Reviewed By No LOINC Needed
32944 HTR2 Genotype 69047-9

Clinical Information

Treatment with specific antidepressant and antipsychotic medications is often guided empirically. Despite the wide array of drugs available for treatment, some patients do not initially respond to treatment, and others who respond early may eventually relapse or develop serious side effects. Antidepressant selection may be more effectively guided by genotyping polymorphic genes encoding several cytochrome P450 enzymes, the serotonin transporter, and the serotonin (5-hydroxytryptamine) receptors HTR2A and HTR2C.(1)


Drugs that bind to the serotonin receptors have a wide range of effects including altering the activation of the receptors, rendering them more or less sensitive to drug concentration, or blocking the receptor. Variations (polymorphisms) in the genes that encode for the serotonin receptor have been associated with different types of drug responses including:

-Allelic variation in the HTR2A gene has been reported to affect response to selective serotonin reuptake inhibitors (SSRI) and risk for adverse drug reactions.(2) Patients predicted to respond poorly to SSRIs due to polymorphic variants in the HTR2A/2C serotonin receptors may be considered for switching to non-SSRI antidepressants. Allelic variation in the HTR2A gene has been linked with response to the antipsychotic drugs clozapine and aripiprazole.(3)

-Treatment with antipsychotics results in significant weight gain (2-3 kg/m[2]) in some patients. Weight gain has been positively correlated with a polymorphism in the promoter of HTR2C (-759C).(4)


Allele nomenclature


Nucleotide Change

Amino Acid Change



Promoter polymorphism





IVS2+54538 A>G







Promoter polymorphism


An interpretive report will be provided.


For additional information regarding pharmacogenomic genes and their associated drugs, please see the Pharmacogenomics Associations Tables in Special Instructions. This resource also includes information regarding enzyme inhibitors and inducers, as well as potential alternate drug choices.

Clinical Reference

1. Malhotra AK, Murphy GM Jr, Kennedy JL: Pharmacogenetics of psychotropic drug response. Am J Psychiatry 2004;161(5):780-796

2. Murphy GM Jr, Kremer C, Rodrigues HE, et al: Pharmacogenetics of antidepressants medication intolerance. Am J Psychiatry 2003;160(10):1830-1835

3. Arranz MJ, Murno J, Birkett J, et al: Pharmacogenetic prediction of clozapine response. Lancet 2000;355(9215):1615-1616

4. Reynolds GP, Zhang ZJ, Zhang XB: Polymorphism of the promoter region of the serotonin 5-HT2C receptor gene and clozapine-induced weight gain. Am J Psychiatry 2003;160:677-679

5. Segman RH, Heresco-Levy U, Finkel B, et al: Association between the serotonin 2A receptor gene and tardive dyskinesia in chronic schizophrenia. Mol Psychiatry 2001;6(2):225-229

6. Segman RH, Heresco-Levy U, Finkel B, et al: Association between the serotonin 2C receptor gene and tardive dyskinesia in chronic schizophrenia: additive contribution of 5-HT2Cser and DRD3gly alleles to susceptibility. Psychopharmacology 2000;152(4):408-413

7. Choi MJ, Kang RH, Ham BJ, et al: Serotonin receptor 2A gene polymorphism (-1438A->G) and short-term treatment response to citalopram. Neuropsychobiology 2005;52:155-162

8. McMahon FJ, Buervenich S, Charney D, et al: Variation in the gene encoding the serotonin 2A receptor is associated with outcome of antidepressant treatment. Am J Hum Genet 2006;78:804-814

Analytic Time

2 days (not reported on Saturday or Sunday)

Method Name

Polymerase Chain Reaction (PCR) with Allele-Specific Primer Extension (ASPE)


New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: