ADVERSE EFFECTS OF THE DRUGS

DEFINITON- ADVERSE EFFECTS

• An adverse drug reaction (ADR) can be defined as a harmful or unpleasant reaction resulting from the drug Administration.
• Adverse effects usually predict hazard from future administration and warrant prevention, or specific treatment, or alteration of the dosage regimen, or withdrawal of the drug.

The various adverse effects of the drugs are as follows:

1. Augmented effects

2. Bizarre effects

3. Chronic Effects

4. Delayed effects

5. Withdrawal effects

6. Failure effects

1. Augmented: Type A (augmented) reactions result from an exaggeration of a drug's normal pharmacological actions when given at the usual therapeutic dose and are normally dose-dependent.

• E.g. Respiratory depression with opioids or bleeding with warfarin.

2.   Bizarre: Type B (bizarre) reactions are novel responses that are not expected from the known pharmacological actions of the drug & are less common.

• E.g. Urine colour changes to Orange or red with phenazopyridine (Pyridium) 

3. Chronic: Type C (Chronic) Dose and time-related reactions, due to dose accumulation, or with prolonged use.

• E.g. adrenal suppression with corticosteroids.

4. Delayed: Type D (delayed):  Time related reactions, i.e. due to prolonged use in a drug which doesn't tend to accumulate.

• e.g.. tardive dyskinesia from antipsychotics

5. Withdrawal: Type E (End of Use), i.e. the undesired effects of ceasing the drug.

·         e.g. opiate withdrawal

6. Failure: Type F (Unexpected failure) of therapy, where a drug undesirably increases or decreases in efficacy

·         e.g. the decreased clearance of a drug by dialysis, or the decreased effect of antibiotics due to resistance.

Toxic Effects of Drug

• Drug toxicity refers to the level of damage that the drug can cause damage to the body.
• The toxic effects of a drug are dose-dependent and can affect an entire system as the CNS or a specific organ such as the liver.
• Drug toxicity usually occurs at doses that exceed the therapeutic efficacy of a drug; however, toxic and therapeutic effects can occur simultaneously.
•  It can be assessed at the behavioural or physiological level. Behaviorally, drug toxicity can be exhibited as decrease in locomotor activity, loss of motor coordination, cognitive impairment.
• Physiological effects include lesions to tissue, neuronal death, and disrupted hormonal cycles.