Every drug is prescribed as a therapy for a particular disease or illness. However, drugs or medications sometimes have an adverse effect on the body and the patient to whom the drug was administered may experience symptoms that not only cause pain and discomfort, but might even turn fatal. One problem with the side effects of medications is that they are never the same for everyone. The severity of side effects depends on a variety of factors, including the age of the person in question, his gender, and food habits. Side effects may appear anytime during the course of medication. If a patient exhibits side effects of a particular drug, the physician either reduces the prescribed dosage or replaces the drug altogether with a milder one. What are Prescription Drugs? Normally drugs are of two types, based on their availability: prescription drugs and over-the-counter drugs. While over-the-counter drugs are easily available from any pharmacy shop, prescription drugs are meant to be sold only if prescribed by a registered medical practitioner. While drugs that are available over the counter, have relatively milder side effects, the side effects of prescription drugs can be severe and in some cases, might even lead to death. Before a prescription drug reaches the market, it is mandatory for the pharmaceutical company that manufactures the drug, to present a list of all the probable side effects of the drug, to the Food and Drug Administration (FDA). The FDA approves the release of the drug if and only if it is convinced that the therapeutic benefits of the drug far outweigh its few side effects. The possible side effects of a newly developed prescription drug, comes to the fore during the clinical tests conducted by the pharmaceutical company. These tests are carried out on thousands of people, mostly adult men, who are administered doses of the drug and kept under observation. Even if a particular drug is found to be relatively safe, after analyzing the results of the clinical test, the possibility of some fatal side effects cannot be completely ruled out. Another risk factor is the use of certain prescription drugs as 'off-label' drugs. This means that the drugs are prescribed for purposes other than the one for which it was tested. While it is not illegal to prescribe off-label drugs, administering such drugs calls for special caution. Side Effects of Prescription Drugs Before taking any prescription drug, it is highly recommended that you are completely aware of all of its possible side effects. Based on their purpose, prescription drugs can be divided into 4 main categories: analgesics, antibiotics, anti-cholesterol and antidepressants. Let's have a look at some of the prescription drug side effects according to the different categories of drugs and their therapeutic purpose.

Type of Drug	Side Effects
Analgesics: These are painkillers that are prescribed as a relief from pain.	Inflammation Risk of heart attack Liver problems Kidney problems Weight gain Increased appetite
Antibiotics: These are drugs that are prescribed as a treatment for infections caused by bacteria.	Diarrhea and vomiting Fungal infections Kidney problems Blood disorders Deafness, though in extremely rare cases
Anti-cholesterols: These are drugs used to reduce the level of fat and cholesterol in blood. Also known as statins.	Fever and headache Digestive tract disorders Nausea and vomiting Muscle pain and inflammation Liver problems Mild depression Sleeplessness
Antidepressants: These drugs are used to treat various psychiatric disorders associated with depression and anxiety.	Dizziness Weakness and fatigue Nausea and vomiting Diarrhea and dehydration Loss of appetite Kidney problems

Thus, we see that no prescription drug is free from side effects. Also, there are certain foods that must be avoided when you are on medication. This is because such foods are eliminated by the cytochrome P-450 enzyme pathway, the same pathway in the liver through which prescription drugs are eliminated from the body, thus increasing the load on the liver. Also, intake of more than one drug simultaneously can prove to be harmful to the body. Thus, it is recommended that you take your doctor's advice before the intake of these drugs, to avoid serious prescription drug side effects.