Adverse reactions to medications

There are various ways in which an individual can experience adverse reactions to medications, whether over-the-counter or prescribed. Most of these effects are not considered as an allergy.

Increased drug effect

It is important to note that some individuals are more affected by drugs than others. It simply means that there is a huge degree of individual differences. Some individuals eliminate drugs at a slower rate than others and levels of the drug can build up over time. Remember that a dose of a drug that suits one individual might be too much or too little for another.

Adverse reaction to medications

The usual side effects include itching, rashes, vomiting, diarrhea, headaches, lethargy and blurry vision.

The possibility for toxic effects is unlikely as the doses prescribed take into consideration this variation and allow a wide margin of safety. Nevertheless, a particular sedative that makes an individual sleep for a few hours might make another individual sleep for a longer period. This would be an increased effect instead of an allergy or intolerance.

What are the side effects?

All medications can cause certain side effects due to the manner on how they work. Many individuals will not experience any of the effects or only a few, but some are prone to the effects. The usual side effects include itching, rashes, vomiting, diarrhea, headaches, lethargy and blurry vision. Take note that all the known side effects of a particular drug are listed in the patient information.

If the individual suffers from a rash and itching after taking a particular drug, it can be difficult to decide if this is a side effect or an allergy. Morphine is also known to trigger itching but this is not an allergy and the drug can still be used. Among children, rashes that are experienced while taking antibiotics are believed to be caused by an underlying viral illness.

Drug interactions

Many drugs are known to react in some way with others. Some of these interactions can be severe that different drugs are not given together. If an individual is taking more than one drug and experiences unusual symptoms, it is best to check whether an interaction is responsible.


There are some drugs that should not be used in certain illnesses since they could not be properly eliminated particularly those who have liver or kidney disease since it can lead to issues for the fetus among pregnant women or they are known to trigger side effects in certain illnesses.


Some individuals are genuinely allergic to a particular drug. Remember that this quite common and most cases of allergy to drugs are due to various mechanisms.

Some drugs such as penicillin, vaccines, some anesthetics and other injections used in X-ray techniques are known to cause allergic reactions. If an individual suffers from a severe adverse reaction to a particular drug or a recurrent reaction on various events, this will be considered as an allergy. This must be listed down in the medical notes and the individual should not be given the drug again. Remember that in each group of drugs, there are some that are less likely to trigger allergies.

If the individual suffers from a reaction and not sure what drugs were given, it is best to consult a doctor or bring him/her to a hospital.


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