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Drugs

TYPES OF REACTIONS

TO DRUGS (MEDICINE)

There are various possible reactions to medicine:

In theory, all medicine or drug can potentially induce a reaction but not all are a true allergy (IgE mediated).

Indeed some reactions are due to metabolic intolerance (e.g. non steroid anti-inflammatory drugs); or are a result of the drug’s side effects, or result from skin lesions not related to the drugs.

Penicillin

Allergic reactions to penicillin are immediate, mediated by specific IgE reaction to penicillin, and can be quite severe.

In this type of situation, allergy diagnosis is established for the whole class of β-lactams antibiotics (penicillins and cephalosporins) due to common antigens of these molecules.

After anamnesis (patient medical history), diagnosis of allergy is confirmed by skin prick-tests as well as by specific IgE dosage (blood test). Depending on the situation, it may be also necessary to practice an Oral provocation test.

Which treatment?

As a principle: strict eviction of penicillin

If absolutely necessary, the drug can be re-introduced in increasing amounts under very close medical supervision, so as to obtain a tolerance of the immune system (i.e. same as a desensitization) .

INTOLERANCE TO

NON STEROID ANTI-INFLAMMATORY DRUGS

(NSAI)

Analgesics family of NSAIDs (Aspirin ®, Voltaren ®, Brufen ®, etc..) can induce “intolerance” reactions.

We are not talking here of allergic reactions in a strict sense, because there are no specific IgE against these molecules. Instead, it is rather a metabolic disturbance, inducing the reaction. Such intolerance reactions can be extremely severe, with asthma and lowered blood pressure.

When the anamnesis shows a systemic reaction with asthma resulting from NSAID use, the diagnosis of intolerance is accepted without further examination.

In other cases, the diagnosis is confirmed by an oral provocation test: increasing doses of the substance are given orally, under close medical supervision. Skin tests are of no use in this situation.

Which treatment?

In case of intolerance, treatment consists in strict avoidance of incriminated drug.

If pain relief is necessary, substances from other families are to be preferred by the physician (paracetamol, cox-2, corticoïdes, morphine).

Reaction to anaesthesia is unfortunately frequent, either local (e.g. dentist) or geneal (surgery).

Local Anaesthesia

Molecules involved belong to the lidocaine family (xylocaine, bupivacaine, etc.).

True allergy (IgE-mediated) to these molecules has not yet been formally demonstrated. We are therefore most often confronted to local intolerance reactions.

Therefore, the allergy diagnosis can only be established through a medically-supervised provocation test (injection of small quantities).

General Anaesthesia

Systemic reactions during general anesthesia are relatively common and require full investigation. After determining the list of molecules administered, it is primordial to single out the one responsible of the reaction. In general, chronology helps identify the problem. Then, diagnosis is confirmed mostly by skin tests.The molecules mainly involved: curare and ammonium.

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