PGx carbamazepine

HLA-B*15:02 positive

• Carbamazepine should generally be avoided in carbamazepine-naïve patients.
• Alternative medications should be considered.
• The FDA recommends screening individuals from genetically at-risk populations before starting therapy.
• The result should be documented in the patient’s medical record.

HLA-A*31:01 positive

• The risk of carbamazepine-induced hypersensitivity reactions is increased.
• The benefits and risks of carbamazepine therapy should be carefully evaluated.
• Alternative treatment options may be considered depending on the clinical situation.

Negative for HLA-B15:02 and HLA-A31:01

• The genetic risk of carbamazepine-induced hypersensitivity is reduced but not eliminated.
• Carbamazepine may be prescribed according to standard treatment guidelines.
• Routine clinical monitoring remains appropriate because severe reactions can rarely occur in individuals lacking these alleles.

The implementation of HLA screening has substantially improved the prevention of severe carbamazepine-induced cutaneous adverse reactions in susceptible populations.

A negative test result does not completely exclude the possibility of carbamazepine-induced hypersensitivity because additional genetic and non-genetic factors may contribute to adverse reactions. Clinical monitoring remains essential regardless of genotype.

Furthermore, many individuals who carry HLA-B 15:02 or HLA-A 31:01 will never develop hypersensitivity reactions, indicating that genotype is an important risk factor but is not solely predictive of clinical outcome.

Role of genetic testing

Pharmacogenetic testing before carbamazepine treatment is an important strategy for minimising the risk of severe cutaneous adverse drug reactions.

Current recommendations support testing:

• Before initiating carbamazepine therapy in patients from populations with increased HLA-B*15:02 prevalence.
• When evaluating treatment alternatives in genetically susceptible patients.
• As part of personalised medicine approaches to improve medication safety.

Frequency of HLA-B*15:02

The prevalence of HLA-B*15:02 varies substantially across ethnic groups.

Reported frequencies include:

• Greater than 15% in parts of Thailand, Malaysia, Hong Kong, and the Philippines.
• Approximately 10% in Taiwan.
• Approximately 2-4% in many South Asian populations.
• Less than 1% in Japanese and Korean populations.
• Rare in most individuals of European, African, and Hispanic ancestry.

Frequency of HLA-A*31:01

The HLA-A*31:01 allele is more broadly distributed worldwide.

Reported frequencies include:

• More than 15% in some Japanese, Native American, Southern Indian, and certain Arab populations.
• Up to approximately 10% in European, Korean, Han Chinese, Latin American, and other Indian populations.
• Approximately 5% in African American populations.

Because these HLA variants are present in healthy individuals who may never receive carbamazepine, the alleles themselves are not disease-causing. Their clinical significance becomes relevant when carbamazepine treatment is considered.

Genetic testing provides clinically actionable information that may help physicians select safer therapeutic alternatives and reduce the risk of severe and potentially life-threatening adverse drug reactions.

Results are interpreted in the individual clinical context, and treatment decisions remain the responsibility of the treating physician.

• U.S. Food and Drug Administration (FDA). Carbamazepine Prescribing Information (Tegretol®, Carbatrol®): HLA-B*15:02 screening recommendations and hypersensitivity warnings. Available from: ,
• Clinical Pharmacogenetics Implementation Consortium (CPIC). Clinical Pharmacogenetics Implementation Consortium Guideline for HLA Genotype and Use of Carbamazepine and Oxcarbazepine: 2017 Update. Available from:
• Dean L. Carbamazepine Therapy and HLA Genotype. Medical Genetics Summaries. NCBI Bookshelf. Updated 2025. Available from: ,
• PharmGKB. Annotation of CPIC Guideline for carbamazepine and HLA-A, HLA-B. Available from:
• PharmGKB. Annotation of FDA Label for carbamazepine and HLA-A. Available from: