Category Archives: Adverse drug reactions and poisoning

POISONING

In most hospitals in the Western World the commonest reason for acute admission of young people to a medical ward is acute poisoning. Such poisoning is usually by selfadministration of prescribed or over-the-counter medicines. Occasionally, however, toxic agents are accidentally ingested or inhaled at home or work or are administered with criminal intent. The types of poisoning. Self-poisoning is usually a cr

Reduction of Adverse Drug Reactions

The incidence of adverse drug reactions can be reduced by: • The development and marketing of safer drugs by the pharmaceutical industry • Tighter control by drug-regulatory authorities within government on the licensing, promotion and marketing of drugs In addition, the doctor must think carefully about every drug he or she prescribes. The hazards of adverse drug reaction can be substantially reduced by:

Monitoring adverse drug reactions

Clinical trials of new drugs are conveniently classified into: PHASE 1: in which the drug is given to a small number of normal volunteers in closely controlled and supervised conditions to study its kinetics and pharmacological effects. PHASE 2: in which the drug is given to a relatively small number of patients with the disease for which its use is proposed. The therapeutic efficacy, correct dosage and phar

Influence of disease on adverse drug reactions

Disease processes may increase the risk and severity of adverse drug reactions in three ways. 1 Disease may lead to changes in the pharmacokinetics of a drug. A reduction in protein binding or reduced renal or hepatic clearance will potentiate the effects of certain drugs. 2 Changes in receptor density and function may occur. For example, there is evidence that the enhanced bronchoconstrictor effects of J3-adr

Protein binding

Many drugs are loosely bound to plasma and tissue proteins. The free unbound fraction is pharmacologically active. This fraction is increased in conditions in which hypoproteinaemia occurs. Competition between drugs for common binding sites can lead to a transient increase in free levels of one following its displacement by another, but the clinical importance of this is uncertain because increased clearance

Neonates

In the neonatal period, drug-metabolizing enzymes may be deficient for at least a month after birth, particularly in the premature neonate. Neonates have problems in effectively metabolizing vitamin K analogues, sulphonami des, barbiturates, morphine and curare. One of the most dramatic examples is the production of the ‘grey baby’ syndrome by chloramphenicol in premature infants. This consists o

Factors influencing dosedependent adverse drug reactions

Formulation The active agent represents only a small proportion of the total weight of a tablet or capsule .. Similarly, drugs for injection require solubilization or suspension in a fluid vehicle of varying complexity. Other constituents of dosage forms, called excipients, are not necessarily inert, and may play an important part in facilitating or hindering  the absorption of a drug. The proportion of an a

Pseudoallergic reactions

In some susceptible patients, substances mimic the allergic reactions described under dose-independent reactions but without the same immunological mechanisms occurring. Unlike allergic reactions they occur on first contact with a drug rather than after previous sensitizing exposure. Susceptibility to such a reaction appears to be determined by genetic and environmental factors. These reactions are produced

Classification

Adverse drug reactions can be classified in several ways. They may be divided into reactions due to: • Overdosage • Intolerance • Side-effects • Secondary effects • Idiosyncrasy • Hypersensitivity Another system of classification divides them into two types: 1 Type A: the results of an exaggerated but otherwise normal pharmacological action of a drug 2 Type B: totally aberrant effects not expected fr

Adverse drug reactions and poisoning

ADVERSE DRUG REACTIONS The size of the problem Any substance that possesses useful therapeutic effects may also produce unwanted, toxic or adverse effects. The incidence of adverse drug reactions in the population is not really known. A survey of 1160 patients given a variety of drugs showed that the incidence of adverse reactions increased with age from about 3% in patients 10- 20 years of age to about 20%