Although prescription drugs save millions of live every year still it cannot be ignored that instances of reactions from these drugs are on the rise. Drug reactions are of two types: allergic and toxic. 
Allergic drug reactions are not dependent on the dose of medication, and are totally unpredictable. Drug toxicity, on the other hand, can often be related to the dose and duration of medication used.
The FDA has yet not been able to decipher the exact reason for this rise in instances. It can be that drugs are not being tested properly before being released into the market. Side effects from new drugs cannot be anticipated that accurately as individuals vary greatly in their reactions to chemical substances. Also rare side effects may not appear in a small group of people that they are tested on but may become painfully obvious when millions of people start taking the drug. A huge number of drugs are being prescribed these days and on an average a patient suffering from common cold and flu has 6-7 different prescription drugs each year.
Drug reactions can range from a minor annoyance to a life threatening situation. The occurrence of an allergic reaction to a drug almost always means that the medication should not be taken again. Toxic effects of medications can usually be managed by either discontinuing the offending drug OR decreasing the dosage. Patients should very carefully report any new symptoms to their doctor while taking a medication and also inform them about any other medication they are currently undergoing to avoid drug interactions.
Via:CBS
