Pharmacy Insights with Chulalongkorn University: Different Bodies, Different Reactions to Medicine

In today’s modern world, where medical science is advancing rapidly, one of the emerging fields that is significantly transforming treatment approaches is pharmacogenomics. This is the study of how an individual’s genetic makeup influences their response to drugs. Its ultimate goal is to provide treatment that is precise, safe, and maximally effective. Although the term “pharmacogenomics” is relatively new and complex, the concept resonates with Thai wisdom familiar to us for generations. We have a saying: “Different bodies favor different medicines”, meaning that people respond differently to the same treatment. The same medication may work well for one person, but be ineffective for another, or even cause an allergic reaction.

Genetics and Drug Response

Genetics—or a person’s DNA—can affect how drugs are absorbed, metabolized, eliminated, and how they act in the body. Even small variations in DNA sequences can have significant effects on both drug efficacy and safety. For example, two people may take the same drug at the same dosage, but the outcomes can be completely different. This becomes especially important with certain high-risk medications.

Case Study: Allopurinol

Allopurinol is a drug used to lower uric acid levels in the blood and treat gout. While generally effective, in some people it can trigger severe, life-threatening allergic reactions. Those carrying the HLA-B58:01 gene variant are at high risk of developing severe drug-induced skin reactions, such as Stevens-Johnson Syndrome or Toxic Epidermal Necrolysis—conditions that cause widespread skin peeling, inflammation, and may be fatal. Around 16% of Thais carry this genetic risk. Therefore, genetic testing is essential before prescribing allopurinol. If testing shows high risk, the drug should be avoided and an alternative used. This genetic screening is now supported by the National Health Security Office (NHSO) for newly diagnosed gout patients and is being implemented in several hospitals nationwide.

Other High-Risk Medications

• Carbamazepine: An anti-epileptic drug. Some Southeast Asian populations, including Thais, carry genetic variants that put them at high risk of severe allergic reactions. Genetic testing before use is strongly recommended.
• Clopidogrel: A medication used to prevent blood clots in heart disease patients. Certain genetic variants among Thais can reduce the drug’s effectiveness, increasing the risk of recurrent heart attacks. Genetic testing helps doctors choose more suitable alternatives.

Conclusion

The saying “Different bodies favor different medicines” is not merely old wisdom, but is now scientifically validated through pharmacogenomics. Today, genetic testing prior to prescribing certain drugs can prevent life-threatening allergic reactions. It also enables physicians to select the right drug and dosage tailored to a patient’s genetics—reducing healthcare costs and preventing unnecessary side effects.

Assoc. Prof. Dr. Nattada Areepiam, RPh, PhD

Assoc. Prof. Dr. Bodin Tiwsoowan, RPh, PhD

Faculty of Pharmaceutical Sciences, Chulalongkorn University