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IJRPC 2011, 1(3) Srinivasan et al. ISSN: 22312781 II. Causality Assessment Between Drug and Suspected reaction 23 Causality assessment is the method by which the extent of relationship between a drug and a suspected reaction is established. It is often difficult to decide if an adverse clinical event is an ADR or due to deterioration in the primary condition. Furthermore, if it is an ADR, which medicine caused it, as many patients are on multiple new medications when ill, particularly if admitted to hospital. In spite of these problems, the decision that a particular drug caused an ADR is usually based on clinical judgment alone. Studies have shown that there is a lot of variation in between rater and within rater decisions on causality of ADRs; this applies both to pharmacologists and physicians 25,26 . There are various approaches in the first approach an individual who is an expert in the area of ADRs would evaluate the case. In the process of evaluation, he or she may consider and critically evaluate all the data obtained to assess whether the drug has caused the particular reaction. A panel of experts adopts a similar procedure to arrive at a collective opinion. using algorithms including standardization of methods. Algorithms being structured systems specifically designed for the identification of an ADR, should theoretically make a more objective decision on causality. As such algorithms should have a better between and within rater agreement than clinical judgment. A number of algorithms or decision aids have been published including the Jones’ algorithm, 28 the Naranjo algorithm, 27 the Yalealgorithm, 29 the Karch algorithm, 30 the Begaud algorithm, 31 the ADRAC, 32 the WHO- UMC, 33 and a newer quantitative approach Algorithm.34 Each of these algorithms has similarities and differences. And the most commonly used algorithms; the Naranjo algorithm (Fig :1) is shown below The Naranjo Algorithm is a questionnaire designed by Naranjo et al for determining the likelihood of whether an ADR (adverse drug reaction) is actually due to the drug rather than the result of other factors. Probability is assigned via a score termed definite, probable, possible or doubtful. Values obtained from the algorithm are sometimes used in peer reviews to verify the validity of author’s conclusions regarding adverse drug reactions. It is also called the Naranjo Scale or Naranjo Score. III. Documentation of ADRs in Patient’s Medical Records This aids as reference for alerting clinicians and other health care professionals to the possibility of a particular drug causing suspected reaction. IV. Reporting Serious ADRs to Pharmacovigilance Centres / ADR Regulating Authorities According to FDA, a serious reaction is classified as one which is fatal, life threatening, prolonging hospitalisation, and causing a significant persistent disability, resulting in a congenital anomaly and requiring intervention to prevent permanent damage or resulting in death 35 Hatwig SC, Seigel J and Schneider PJ categorised ADRs into seven levels as per their severity. Level 1&2 fall under mild category whereas level 3& 4 under moderate and level 5, 6&7 fall under severe category . 36 (fig:2). Karch and Lasanga classify severity into minor, moderate, severe and lethal. In minor severity, there is no need of antidote, therapy or prolongation of hospitalisation. To classify as moderate severity, a change in drug therapy, specific treatment or an increase in hospitalization by at least one day is required. Severe class includes all potentially life threatening reactions causing permanent damage or requiring intensive medical care. Lethal reactions are the one which directly or indirectly contributes to death of the patient. Different ADR regulatory authorities are - Committee on safety of medicine (CSM), Adverse drug reaction advisory committee (ADRAC), 37 MEDWATCH, Vaccine Adverse Event Reporting System 38 WHO-UMC international database maintains all the data of ADRs. CONCLUSION India has more than half a million qualified doctors and 15,000 hospitals having bed strength of 6, 24,000. It is the fourth largest producer of pharmaceuticals in the world. It is emerging as important clinical trial hub in the world. Many new drugs are being introduced every year and so every health care professional must have knowledge about importance of ADR monitoring and pharmacovigilance. Every health care professional should see it as a part of his/her professional duty keeping in mind about Hippocrates admonition” at least does no harm”. 609
IJRPC 2011, 1(3) Srinivasan et al. ISSN: 22312781 Table 1: Characteristics of Type A and Type B Adverse Reactions Characteristics Type A Type B Dose dependency Usually shows good relationship No simple relation ship Predictable from known pharmacology Yes Not usually Host factors Genetic factors might be important Dependent on host factors Frequency Common Uncommon Severity Variable but usually mild Variable, proportionately more severe Clinical burden High morbidity and low mortality High morbidity and mortality Overall portion of adverse drug reaction 80% 20% First detection Phase1-III Phase IV, occasionally phase III Animal models Usually reproducible in animals No known animal models Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 Level 7 Table 2: Hartwig’s Severity Assessment Scale An ADR occurred but required no change in treatment with the suspected drug. The ADR required that treatment with the suspected drug be held, discontinued, or otherwise changed. No antidote or other treatment requirement was required. No increase in length of stay (LOS) The ADR required that treatment with the suspected drug be held, discontinued, or otherwise changed. AND/OR An Antidote or other treatment was required. No increase in length of stay (LOS) Mild= level 1 and 2, moderate= level 3 and 4, severe= 5, 6 and 7. Any level 3 ADR which increases length of stay by at least 1 day . OR The ADR was the reason for the admission Any level 4 ADR which requires intensive medical care The adverse reaction caused permanent harm to the patient The adverse reaction either directly or indirectly led to the death of the patient 1) Are there previous conclusive reports of this reaction? If YES = +1, NO = 0, Do not know or not done = 0 2) Did the adverse event appear after the suspected drug was Given? If YES = +2, NO = -1, Do not know or not done = 0 3) Did the adverse reaction improve when the drug was discontinued or a specific antagonist was given? If YES = +1, NO = 0, Do not know or not done = 0 4) Did the adverse reaction appear when the drug was Re-administered? If YES = +2, NO = -2, Do not know or not done = 0 5) Are there alternative causes that could have caused the reaction? If YES = -1, NO = +2, Do not know or not done = 0 6) Did the reaction reappear when a placebo was given? If YES = -1, NO = +1, Do not know or not done = 0 7) Was the drug detected in any body fluid in toxic Concentrations? If YES = +1, NO = 0, Do not know or not done = 0 610
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