But even when a drug is designed to target a specific protein can sometimes impact with others, is what causes side effects.

This is the way we operate some of the Most Common Drugs:

Weight loss

Drugs for weight control function through interaction with specific proteins. The orlistat weight loss drug, marketed as Xenical or Alli, blocks the action of pancreatic lipase, which reduces the amount of fat absorbed from food.

Antihistamines and antidepressants

Loratadine relieves allergy symptoms by blocking the histamine receptors. Antidepressants such as Prozac affect serotonin receptors, and beta-blockers used to treat heart disease, act on the adrenergic receptor.


They attack the proteins that are found only in the specific bacteria or virus that are crucial for the survival or multiplication of the microbe. In other cases, the objective is an enzyme, which are only proteins that speed up chemical reactions.

Penicillin, for example, binds to and blocks an enzyme that builds bacterial cell walls, causing the bacteria susceptible to rupture and die.

Cancer drugs

Many drugs work by killing cancer cells divide more rapidly, but can also affect healthy cells. For example, paclitaxel (Taxol), which is prescribed for breast, ovarian and other types, act by binding to a protein known as tubulin inhibiting the formation of structures called microtubules are necessary for cell division.

The newer drugs for cancer are more demanding and its design is based on years of experiments in basic biology of how cancer cells grow.


Cholesterol lowering drugs such as atorvastatin and simvastatin, block the action of HMG-CoA reductase, an enzyme involved in the production of cholesterol.