Almost any drug can cause an adverse reaction. Reactions range from irritating or mild side effects such as nausea and vomiting to life-threatening a… - Chinedum Babalola

One thing that is important to note is that drugs are poisons; there is no drug that really does not have its side effect. That is why the drug regulatory body based on pharmacovigilant sometimes recall some drugs from the market if high levels of adverse drug reactions are reported.

Most allergic reactions occur within hours to two weeks after taking the medication and most people react to medications to which they have been exposed to in the past. This process is called “sensitisation.” However, rashes may develop up to six weeks after starting certain types of medications. Rarely, blisters and bleeding inside the skin or the inner surfaces of the intestines may occur. Unfortunately, if it is the life threatening anaphylaxis, it could be fatal. So, it is important to educate people about these possible reactions to drugs.

Also, the rate at which the body is able to breakdown a drug could be genetic modified. So, it is possible based on a person’s genetic makeup to predict those that may react to some drugs. This makes some people’s reaction to particular drugs genetically.