Side effects of medications prescribed for hypertension and diabetes can range from the more commonplace nausea or dry mouth to something more frustrating and difficult to manage: weight gain. That is if you are genetically inclined to do so.

How our body responds to a particular drug is determined to some extent by our genes. Two patients who consume the exact same dose of a particular drug can react or respond in completely different ways. The reason for this variability in drug response is a complex interaction between all the factors in play: genetics, diet, environment, and properties of the drug itself.

How medication contributes to weight gain

A particular drug, or combination of drugs, can affect your weight by: 

• Sapping your energy
• Amplifying your body’s hunger signals or reducing the feelings of satiety and fullness -Making you crave certain foods or just making you want to eat more
• Promoting fat storage
• Disrupting your body’s fluid retention and release mechanisms 

Your weight can be influenced by commonly prescribed medications such as antidepressants, corticosteroids, antipsychotics, hormone therapy, anti-epileptics, diabetes medicines, and certain hypertension medications.

Pharmacogenetics and Pharmacogenomics

You may have heard of these two terms in the context of precision medicine.

The branch of biomedical science that studies how people respond differently to drug therapy based on their genetic profile is called Pharmacogenetics. The term Pharmacogenetics usually refers to how variation in one single gene influences the response to a single drug.

Pharmacogenomics is a broader definition. The field studies how all of the genes belonging to the human genome can influence how we respond to drugs. The multiple variations in our genes can affect different aspects of drug response:

• how efficiently the drug can reach its target area in our body
• how rapidly our system can metabolize the drug
• how much of it we actually absorb and
• whether it is enough to see a difference 

Genetic tests have appeared lately that report on 33 genetic variants associated with the drug response to commonly prescribed drugs such as blood thinners. However, the data they provide is not yet absolute and has limited practical use. There is not enough data to support medication choice or changes in medication based on these tests. The tests also do not agree on what medical recommendations should be made upon detecting a particular gene variant.

The American Psychiatric Association recently published a review which concludes that there is not enough evidence to support the mainstream use of pharmacogenetic tests at the moment. Even with non-psychiatric drugs, there are more questions than absolute answers.

The potential for devising medicinal treatment strategies linked to genetics does exist. However, more research and data are warranted before it becomes the norm.

Whether you suspect that a particular medication is causing your unexpected weight gain, or whether you run a test to check your pharmacogenetic profile, you must not change any prescribed medications on your own without discussing your concerns with your physician.

Since the benefits of the medication for your particular condition may very well outweigh the risk of weight gain, it is the physician’s call whether to continue with that medication or not. Also, review your eating habits, recent food choices, activity, and lifestyle to check whether any other factors may have contributed to your weight gain. If your medication does seem to be responsible for it, your physician can make suggestions to counteract the drug’s unwanted impact on your weight.