ADVERSE DRUG REACTIONS

Adverse drug reactions are classified alphabetically as follows:

A             Augmented pharmacological effects: dose dependant

·         Side effects → at therapeutic dose

·         Toxicity → at high dose

·         Intolerance → toxicity at therapeutic dose

B             Bizarre effects: non dose dependant

·         Drug allergy: 4 types

Anaphylaxis (type I)

Blood cytolysis (type II)

Complex (AG:AB) mediated reaction (type III)

Delayed hypersensitivity (type IV)

·         Idiosyncrasy: Abnormal effect e.g. CNS depressants causing stimulation

C             Chronic effects: Duration dependant

                                Adverse effects of prolonged treatment

                                e.g. Corticosteroids causing immunosuppression

D             Delayed effects:

                                Adverse effects long time after stopping the drug

                                e.g. Carcinogenicity and Mutagenicity by anticancer drugs and radio-isotopes

E              End of treatment effects: Adverse effects due to abruptly stopping the drug e.g. withdrawal

                syndrome of clonidine

F              Foetal effects: Adverse effects on the foetus depend upon the time of maternal drug intake i.e.

                                First ½ month                    → Abortion

                                From ½ - 2 months          → Teratogenicity

                                2 months onwards          → Abnormal growth & development

Drugs causing Agranulocytosis

Agranulocytosis is one of the most severe adverse effects, may be fatal even. Blood cytolysis occurs, especially neutrophils are damaged, predisposing to serious infections.

Following drugs are known to cause AGRANULOCYTOSIS:

A             Antithyroid drugs (Propylthiouracil, Carbimazole, Methimazole)

                ACE Inhibitors

G             Gold salts like Sodium aurothiomalate

R             Radioactive elements like I ¹³¹

A             Alkylating agents

N             Nitrogen mustards like Mechlorethamine, Cyclophosphamide

U             Urethane (obsolete)

L              Largactil (Chlorpromazine)

O             Oxyphenbutazone/Phenylbutazone

C             Chloramphenicol & Clozapine

Y              Yellow drug i.e. Mepacrine (obsolete)

T              Thioureas, Tricyclic antidepressants (TCA)

O             Oxazolidine/Phenytoin

S              Sulphonamides including Co-trimoxazole

I               Indomethacin

S              Sulfones, Sulfonylureas (1^st Generation)

Drug interactions (3 ‘P’ s)

   Pharmaceutical interactions: during formulation or mixing of drugs. The incompatibility can be due to physical or chemical interaction between the compounds.

   Pharmacokinetic interactions: during absorption, distribution, metabolism or excretion of drugs.

   Pharmacodynamic interations: at the receptor site of between the actions of the drugs.