Single nucleotide polymorphisms (SNPs) are small changes in our DNA that happen at just one spot in the genetic code. They are the most common type of genetic difference we see between people.

SNPs can affect how different people respond to medicines. This means that some might need different doses or could have different side effects. Understanding SNPs is really important for personalized medicine. That’s when treatments are adjusted based on a person's unique genetic makeup.

1. Why SNPs Matter for Medicine

SNPs can affect how our bodies process medicine in a few ways:

• How We Break Down Drugs: Many SNPs are found in the genes that help break down drugs. A big group of these genes is called the cytochrome P450 (CYP) family. These genes help the body handle about 75% of all medicines. For example:
  • Some people are called poor metabolizers (PMs). This means their bodies don’t process some drugs well, leading to more side effects.
  • Others are known as ultra-rapid metabolizers (UMs). These people clear drugs from their bodies very quickly, which might make the medicine less effective.

Research shows that around 7-10% of white people are PMs for a specific CYP gene (CYP2D6), while about 1-2% are UMs. This shows how SNPs can cause big differences in how people respond to drugs.

• Effectiveness of Drugs: SNPs can also affect how well a medicine works. For example, some people have a specific SNP in the VKORC1 gene that changes how they react to warfarin, a blood thinner. People with certain variations may need smaller doses of warfarin. Studies suggest that 30-40% of the differences in warfarin dosing are due to these genetic changes.

2. Side Effects from Drugs

SNPs can also make some people more likely to have bad reactions to medicines.

• Example: People with the HLA-B*5701 gene are at a higher risk (about 45% chance) of having serious allergic reactions to abacavir, a medicine for HIV. This shows why it’s important to check for SNPs before giving some medicines, to avoid serious side effects.

3. Changes in Medicine Development and Prescribing

Knowing about SNPs has changed how new medicines are created and how doctors prescribe them. For example:

• Many drug companies now look at genetic differences during medicine testing to see how they might affect safety and effectiveness.
• There are new guidelines that suggest testing for SNPs to choose the right medicine and dose. For instance, doctors are advised to check the CYP2C19 gene before giving clopidogrel to see if it will work for the patient.

4. Real-life Examples

There are many real-life examples that show how SNPs affect drug responses:

• Tamoxifen: Studies show that the effectiveness of tamoxifen, a drug used for breast cancer, can depend on SNPs in the CYP2D6 gene. Patients with certain SNPs may have a 50% higher chance of their cancer coming back than those with normal gene activity.

• Statins: SNPs in the SLCO1B1 gene can greatly change the risk of muscle problems caused by statins. People with a common SNP (rs4149056) might be over 2.5 times more likely to have these issues.

• Antidepressants: SNPs in genes like SLC6A4 and COMT can affect how people respond to antidepressants called SSRIs. About 30% of patients might not respond well to their first treatment because of their genetic differences.

Conclusion

In short, SNPs are very important when it comes to how different people respond to medicines. They can change how drugs are processed, their effectiveness, and the risk of side effects. As scientists learn more about pharmacogenomics (how genes affect drug responses), it’s becoming more important to pay attention to SNPs in healthcare. This will lead to better treatments that work for individual patients and help to reduce unwanted side effects. The future of medicine is moving towards personalized treatments based on our unique genetics.