Tuesday, May 24, 2011

Adverse Drug Reaction its classification, analysis and future trends

Adverse drug reaction (ADR) is defined by WHO as a response to a drug that is noxious and unintended, and occurs at doses normally used in patients for prophylaxis diagnosis or therapy of a disease.

ADR is classified as such-

Type A-Type A (Augmented) Reactions: are those related to exaggerated pharmacological effects of drug & tend to be fairly common (usually more than 1 in 100)

Type B (Bizarre) Reactions: are those that are unexpected & unpredictable, have genetic predisposition, allergy etc., are often serious.

Type C (Chronic) Reactions: which are due to long term use of drug.

Type D (Delayed) Reactions: e.g., teratogenesis, carcinogenesis.

Type E (End of Use) Reactions: which occur when discontinuation of drug is too abrupt.

Some adverse reactions subside with continuous use e.g., drowsiness with paroxetine.Patient has to tolerate sometime mild ADR to obtain appropriate therapeutic response. Some ADR are dose related & disappear if dose reduced.
Some are hazardous & unacceptable, require discontinuation of drug

ADR is analyzed by

COHORT STUDIES where patients taking a particular drug identified and events recorded. Only drawback is that can be done on small number of patients and lack of suitable control. Advantage is that incidence can be determined

CASE – CONTROL STUDIES which are retrorespectve studies where patient with diseases are compared with patients having no diseases. Its disadvantage is that difficult to get control and casualty cannot be ascertained. Advantage is that it requires less time.

USE OF POPULATION STATISTICS like based on the mortality data such as increase in death due to use of B2 agonist. Teratogencity data can also be utilized.

Causalty assessment is done based on the de-challenge and re-challenge of the drug.
Causalty categories like certain, probable and possible is based on the time factor as well as de-challenge and re-challenge.

Post marketing surveillance by pharmaceutical industry detects the ADR which is mandatory for new drugs released in the market. It is useful in generating signals and educating and informing patients. It also identifies the risk factors and the underlying mechanisms.

The science of pharmacovigilance could be enhanced with the availability of systems-based tools that facilitate analysis of aggregate data for purposes of signal detection, signal evaluation and knowledge management. One of the known pharmaceutical company has recently implemented Online Signal Management (OSM) as a data-driven framework for managing the pharmacovigilance of marketed products.

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