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Adverse Drug Reactions - Types of Adverse Drug Reactions

Adverse Drug Reactions - Types of Adverse Drug Reactions


Definition -The adverse drug reactions may be defined as the unwanted undesirable effects of a drug attained at a normal dose.

Onset of Adverse Drug Reactions (ADRs)

Acute: Those ADRs which occur within 60 minutes after administration of the drug.
Sub-acute: Those ADRs which occur between 1 to 24 hours after the administration of the drug.
Latent: Those ADRs which occur for more than 2 days after the administration of the drug.

Seriousness of Adverse Drug Reactions (ADRs)

Mild/minor: These ADRs do not require any treatment.
Moderate: These ADRs require a change in the therapy.
Severe: These ADRs require immediate attention as well as the termination of the ongoing therapy.

TYPES OF ADVERSE DRUG REACTION

The adverse drug reactions are of two major types namely,

1. PREDICTABLE ADRs:

Those ADRs whose response is qualitatively normal but quantitatively abnormal.

Features:

1. It is dose related.
2. It is less common.

Correction:

1. By correction of dose.
2. By withdrawl of drug therapy.

2. UNPREDICTABLE ADRs:

Those ADRs which occur due to the unknown pharmacology of the drug.

Features:

1. It is not dose dependent.
2. It occurs very rarely.
3. It is severe and life-threatening.
4. It includes various types such as idiosyncratic reactions; allergic reactions etc.

CLASSIFICATION OF ADVERSE DRUG REACTIONS

1. SIDE EFFECTS

These occur at therapeutic doses of the drug.
For example:
1. Anticholinergic drugs may lead to dryness of mouth.
2. Anti-ovulatory drugs may cause nausea.

2. IDIOSYNCRASY

It intends to identify individuals who are either more likely or less likely to respond to a drug, as well as those who require an altered dose of certain drugs.
For example:
1. G6PD deficiency is responsible for haemolysis with primaquine.
2. Barbiturates cause excitement and mental confusion in some patients.
3. Quinine causes cramps, diarrhoea, asthma in some patients.

3. INTOLERANCE

It is a reaction occurring just opposite to that of the tolerance phenomena as it increases the sensitivity even at low doses.
For example:
1. Carbamazepine causes ataxia.

4. TOXIC EFFECTS

These are a result of long-term therapy or long-term usage of drugs.
For example:
1. Paracetamol may lead to hepatic necrosis.
2. Morphine may lead to respiratory failure.

5. SECONDARY EFFECTS

These are the indirect effects of any drug therapy, where no direct effect is seen.
For example:
1. Promethazine as anti-allergic leads to sedation.
2. Codeine cough syrups also produce sedative action.

6. DELAYED EFFECTS

These are the effects which are seen years after termination of the drug therapy.
For example:
1. Carcinogenicity.
2. Mutagenicity.
3. Teratogenicity.

7. PHOTOSENSITIVITY

This is again subdivided into two parts:

A. Phototoxicity

In this, the drug accumulates in the skin which absorbs light, leading to the photochemical reaction, leading finally to tissue damage.
For example- erythema

B. Photoallergic

In this, a drug-induced cell-mediated immune response which leads to contact dermatitis on exposure to light.

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