Jain Deepika*, Rathore Kamal Singh
BN Institute of Pharmaceutical Sciences,
Pharmacovigilance is particularly concerned with adverse drug reactions, or ADRs, which are officially described as: “A response to a drug which is noxious and unintended, and which occurs at doses normally used for the prophylaxis, diagnosis or therapy of disease, or for the modification of physiological function”. The mission of Pharmacovigilance is to contribute to the protection of public health in the regulation of the safety; quality and efficacy of medicines for human use and to ensure the healthcare professionals and patients have access to information about the safe and effective use of medicine. The World Health Organization (WHO) defines an adverse drug reaction (ADR) as “Any response to a drug which is noxious and unintended, and which occurs at doses normally used in man for prophylaxis, diagnosis or therapy of disease or for modification of the physiological function”.
The discipline of pharmacovigilance has developed considerably since the 1972 WHO technical report, and it remains a dynamic clinical and scientific discipline. It has been essential to meet the challenges of the increasing range and potency of medicines (including vaccines), which carry with them an inevitable and sometimes unpredictable potential for harm. The following is a summary of some of the serious challenges facing pharmacovigilance programmes in the next ten years & the major challenges are:Globalization, Web-based sales and information, Broader safety concerns, Public health versus pharmaceutical industry economic growth , Monitoring of established products, Developing and emerging countries, Attitudes and perceptions to benefit and harm, Outcomes and Impact.
REFERENCE ID: PHARMATUTOR-ART-1913
‘Not all hazards can be known before a drug is marketed’.
- Committee on Safety of Drugs, Annual Report 1969, 1970.
A pharmaceutical product, used in or on human body for the prevention (prophylaxis), mitigation, diagnosis and/or treatment of disease, or for modification of physiological function.
Medicines have led otiovement in the treatment and control of diseases; they also produce adverse effects on the human body from time to time. Many drugs are precisely targeted to the cause and mechanism of a disease, they may also have minor or distressing effects on other parts of the body, or interact negatively with the various systems of a particular individual or with other drugs or substances that they are taking, or, not work well or at all for some, many or all of those who take them. There is no such thing as a safe drug. There are risks in any intrusion into the human body, whether chemical or surgical. Nothing in this field is entirely predictable - except that the interaction between science and the human body may produce surprises1-3.
Benefits: Benefits are commonly expressed as the proven therapeutic good of a product, but should also include the patient’s subjective assessment of its effects
Risk: Risk is the probability of harm being caused, usually expressed as a percent or ratio of the treated population.
Harm: Harm is the nature and extent of the actual damage that could be caused. It should not be confused with risk.
Effectiveness : Effectiveness is used to express the extent to which a drug works under real world circumstances, i.e., clinical practice (not clinical trials).
Efficacy: Efficacy is used to express the extent to which a drug works under ideal circumstances (i.e. in clinical trials)
Finding the risk of drugs
Pharmaceutical companies are required by law in all countries to perform clinical trials, testing new drugs on people before they are made generally available. The manufacturers or their agents usually select a representative sample of patients for whom the drug is designed, at most a few thousand along with a comparable control group. The control group may receive a placebo and/or another drug that is already marketed for the disease. The purpose of clinical trials is to discover:
If a drug works and how well
If it has any harmful effects, and
Its benefit-harm-risk profile - does it do more good than harm, and how much more? If it has a potential for harm, how probable and how serious is the harm?
Clinical trials in general, tell us a good deal about how well a drug works and what potential harm of the drug, it may cause. They provide information which should be reliable for larger populations with the same characteristics as the trial group - age, gender, state of health, ethnic origin, and so on.
The variables in a clinical trial are specified and controlled and the results relate only to the population of which the trial group is a representative sample. A clinical trial can never tell you the whole story of the effects of a drug in all situations. In fact, there is nothing that could tell you the whole story, but a clinical trial must tell you enough; "enough" being determined by legislation and by contemporary judgments about the acceptable balance of benefit and harm4-9.
Parmakon(Greek), “drug” and vigilare (Latin), “to keep awake or alert, to keep watch.”
Pharmacovigilance is the pharmacological science relating to the detection, assessment, understanding and prevention of adverse effects, particularly long term and short term side effects of medicines. Generally speaking, pharmacovigilance is the science of collecting, monitoring, researching, assessing and evaluating information from healthcare providers and patients on the adverse effects of medications, biological products, herbalism and traditional medicines with a view to1,10-14:
Identifying new information about hazards associated with medicines
Preventing harm to patients
Pharmacovigilance is particularly concerned with adverse drug reactions, or ADRs, which are officially described as: “A response to a drug which is noxious and unintended, and which occurs at doses normally used for the prophylaxis, diagnosis or therapy of disease, or for the modification of physiological function”. Pharmacovigilance is gaining importance for doctors and scientists as the number of stories in the mass media of drug recalls increases15-17.
Because clinical trials involve several thousand patients at most; less common side effects and ADRs are often unknown at the time a drug enters the market. Even very severe ADRs, such as liver damage, are often undetected because study populations are small. Post marketing pharmacovigilance uses tools such as data mining and investigation of case reports to identify the relationships between drugs and ADRs18.
The world health organization (WHO) collects data from 72 countries around the world in an attempt to detect adverse drug reactions (ADRs) signals that are too weak for any individual country to detect. Some of the services provide to the national centers includes-identifying new signals from the information submitted by the national centers, provision of the WHO database, information exchange between national centers and WHO, publications of the newsletters and reports, provision of training and support to the national centers, and annual meeting of the representatives of national centers19.
2. Brief history of Pharmacovigilance in India
Even though pharmacovigilance is still in its infancy, it is not new to India. It was not until 1986 that a formal adverse drug reaction (ADR) monitoring system consisting of 12 regional centers, each covering a population of 50 million, was proposed for India. However, nothing much happened until a decade later when in 1997, India joined the World Health Organization (WHO) Adverse Drug Reaction Monitoring Programmed based in Uppsala, Sweden. Three centers for ADR monitoring were identified, mainly based in teaching hospitals: a National Pharmacovigilance Centre located in the Department of Pharmacology, All India Institute of Medical Sciences (AIIMS), New Delhi and two WHO special centers in Mumbai (KEM Hospital) and Aligarh (JLN Hospital, Aligarh Muslim University). These centers were to report ADRs to the drug regulatory authority of India. The major role of these centers was to monitor ADRs to medicines marketed in India. However, they hardly functioned as information about the need to report ADRs and about the functions of these monitoring centers were yet to reach the prescribers and there was lack of funding from the government. This attempt was unsuccessful and hence, again from the 1st of January 2005, the WHO sponsored and World Bank-funded National Pharmacovigilance Program for India was made operational5, 20-23.
The National Pharmacovigilance Program established in January 2005, was to be overseen by the National Pharmacovigilance Advisory Committee based in the Central Drugs Standard Control Organization (CDSCO), New Delhi. Two zonal centers-the South-West zonal centre (located in the Department of Clinical Pharmacology, Seth GS Medical College and KEM Hospital, Mumbai) and the North-East zonal centre (located in the Department of Pharmacology, AIIMS, New Delhi), were to collate information from all over the country and send it to the Committee as well as to the Uppsala Monitoring centre in Sweden. Three regional centers would report to the Mumbai center and two to the New Delhi one. Each regional center in turn would have several peripheral centers reporting to it. Presently there are 24 peripheral centers24.
Objectives of National Pharmacovigilance Programme
The main objectives of National Pharmacovigilance Programme are as following5
- To foster the culture of Adverse Event (AE) notification and reporting
- To establish a viable and broad based ADR monitoring programs in India
- To create an ADR database for the Indian population
- To create awareness of ADR monitoring among people
- To ensure optimum safety of drug products in Indian market.
- To create infrastructure for ongoing regulatory review of Periodic Safety Updates Regulators (PSURs).
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The mission of Pharmacovigilance is to contribute to the protection of public health in the regulation of the safety, quality and efficacy of medicines for human use and to ensure the healthcare professionals and patients have assess to information about the safe and effective use of medicine25.
Our current ADR reporting system involves a passive approach in which providers are encouraged to report adverse events via e-mail, telephone, or paper. In addition, practitioners may report ADRs directly to a hospital pharmacist who is present in the hospital.
Raise awareness on the magnitude of drug safety problems and increase the rational and safe use of drugs.
Identification of potential safety hazards, evaluation, monitoring and where appropriate, implementation of regulatory action to maximize benefit and minimize risks associated with medicinal products.
Early detection of unknown adverse drug reaction and increase in frequency of known adverse drug reactions
To compare the number of ADRs identified by this traditional passive method
To determine the significance of ADRs those were reported by patients but unknown to their provider.
Convince healthcare professionals that reporting to ADR is their professional and moral obligation.
Identification of risk factors and possible mechanism underline adverse reactions
Aid health professionals in becoming vigilant in the detection and reporting of ADRs and other drug induced problems.
Anticipate the various combinations by which ADRs can be caused
Considering drug-drug interactions and drug-food interactions which may responsible for ADRs
4. Functions of Pharmacovigilance
From early development through post-marketing, we need to master safety information to make critical decisions — and that requires more coordination than traditional safety systems provide. The best approach is one that integrates safety across both time and function. This lifecycle approach keeps precisely informed about product’s safety profile as it evolves — so we can not only meet regulatory and pharmacovigilance requirements, but also achieve our commercial goals2, 26
Fig.1: Different functions of Pharmacovigilance
With Quintiles, we’ll have one point of contact and access to a global array of safety and risk management professionals to help us:
- Monitor safety and manage case reports
- Mitigate risk earlier in development
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5. Adverse Drug Reactions
The World Health Organization (WHO) defines an adverse drug reaction (ADR) as “Any response to a drug which is noxious and unintended, and which occurs at doses normally used in man for prophylaxis, diagnosis or therapy of disease or for modification of the physiological function”. This definition excludes overdose (either accidental or intentional), drug abuse, and treatment failure and drug administration errors. The terms “Adverse Drug Reaction” and “Adverse Drug Event” are not synonymous27.
The WHO definition of an adverse event is “Any untoward medical occurrence that may present during treatment with a pharmaceutical product but which does not necessarily have a causal relationship with this treatment”. As soon as someone suspects a casual relationship between the untoward occurrence and an administered medicine, the event is turn into a suspected adverse drug reaction.
Fig.2: Adverse drug reactions flow chart
Any unintended effect of a pharmaceutical product occurring at doses normally used in humans, which is related to the pharmacological properties of the drug.
Unexpected adverse Reaction
An ‘Unexpected Adverse Reaction’ means an adverse reaction, the nature, severity or outcome of which is not consistent with the Summary of Product Characteristics.
Serious Adverse Reaction
A ‘Serious Adverse Reaction’ means an adverse reaction which results in death, is life threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability or incapacity or is a congenital anomaly/birth defect.
Abuse of Medicinal Products
Abuse of medicinal products’ means the persistent or sporadic, intentional excessive use of medicinal products which is accompanied by harmful physical or psychological effects.
Traditionally, ADRs are classified into two categories
- Type A
- Type B
Type A ADRs
Type A (Augmented) reactions are usually the exacerbation of pharmacological effects of a drug and thus are dose dependent. An example is insulin induced hypoglycemia. These reactions are usually predictable due to the known pharmacology of a drug and thus preventable. The incident of occurrence of type A reactions is high in any society; they are responsible for considerable morbidity. The morbidity rate is relatively low since most type A reactions will disappear by reduction of the dose or by discontinuation of drug.
Type B ADRs
Type B (Bizarre) reactions are hypersensitivity reactions and are not dose dependent. An example of penicillin induced hypersensitivity reaction. These reactions are often not predictable and preventable (unless the patient has a known history of this type of reaction). This type of reaction is rare but often serious with a high mortality rate.
The basic difference between Type A ADRs and Type B ADRs describes
Recently different newer classifications have been proposed. One of these classifications include
Type A (augmented) Type B (Bizarre)
Type C (Continuous) Type D (Delayed effect)
Type E (Rebound effect) Type F (Failure of therapy)
Wills and Brown have proposed another classification on the basis of mechanism into eight new categories which includes
Type A (augmented) Type B (Bizarre)
Type C (Chemical) Type D (Delivery)
Type E (Exit) Type F (Familial)
Type G (Genotoxicity) Type H (Hypersensitivity) Type U (Unclassified)
Table.1: Differentiation between type ADRs and type B ADRS
Type A ADRs
Type B ADRs
These type of reactions are dose dependents.
There is no simple relationship with the dose of the drugs.
They are predictable to known pharmacology.
They are not predictable.
Genetic factors may be important in case of these reactions.
These reactions are dependent on host factors
These reactions are very common in frequency.
These reactions are uncommon in frequency.
They are variable but usually mild.
They are also variable but more severe than type A reactions.
They show high morbidity.
They also show high morbidity.
They possess low mortality.
They posses high mortality.
They calculated as 80% overall proportion of ADRs.
They calculated as 20% of overall ADRS.
These reactions are first detected in phase I & III of clinical trials.
These reactions are detected in Phase IV and occasionally in phase III.
These reactions are usually because of parent drug or stable metabolite.
These reactions may be because of parent drug or stable metabolites.
Factors which predisposing ADRs
There are many factors that can predispose to the occurrence of adverse drug reactions in a patient. Patients who have one or more following predisposing factors are at high risk of developing ADRs.
* Multiple and intercurrent disease
* Drug characteristics
* Race and genetics
Patients with multiple drug therapy are more prone to develop as adverse drug reaction either due to alteration of drug effect through an interaction mechanism or by synergistic effect. The amount of risk associated with multiple drug therapy increases in direct proportion to the number of drug administered4.
Multiple and intercurrent disease
Patient with multiple diseases are at an increased risk of developing an ADR due to multiple drug used for their multiple diseases. Similarly, patients with impaired hepatic or renal status are also at a high risk of developing an ADR to drugs which are eliminated by these organs. For example a patient with decreased renal function who is treated with amino glycosides is at an increased risk of developing nephrotoxicity unless appropriate dosage adjustment is made6,9.
Elderly and pediatric patients are more vulnerable to develop ADRs. Elderly patients are more susceptible to ADRs due to the physiological changes (pharmacokinetics and pharmacodynamic) which accompany aging, and also because they are often taking many drugs for chronic and multiple diseases. Nitrates or angiotensin converting enzyme inhibitor induced postural hypotension in an elderly patient is an example of this kind, where the reaction may be exacerbated by age related impaired baroreceptor responses to a change in posture. Pediatric patient may develop serious adverse drug reactions to some drugs since all children, especially neonates, differ in their drug handling capacity compared to adults. An example of such a serious reaction is the Gray Baby Syndrome with chloramphenicol.
Some drugs are highly toxic in nature and patients who are treated with these drugs are at an increased risk of ADRs. For examples, nausea and vomiting is a common adverse drug reaction seen in patients treated with anticancer drugs. Also, patients who are treated with drugs which have narrow therapeutic index such as digoxin and gentamicin are more susceptible to develop ADRs, as a slight increase in the serum drug concentration of these drugs may result in drug toxicity.
It has been reported that women are more susceptible to develop ADRs, for unknown reasons. Chloramphenicol induced aplastic anemia and phenylbutazone induced agranulocytosis in twice and trice as common, respectively in women patients.
Race and genetics
It is evident that ADRs are more common in genetically predisposed individual. For example, patients who are genetically deficient of Glucose-6-Phosphate Dehydrogenase (G6PD) enzyme are at higher risk of developing hemolysis due to primaquine than those who are not, race and genetic polymorphism may account for alterations in handling of drugs and their end organ effects.
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Mechanism of type A ADRs
A drug suspected to have caused an adverse drug reaction in one patient may not necessarily cause the similar adverse drug reaction in another patient. This is due to inter individual variability, which may predispose an individual to an ADR. Any type A reaction, which occurs in an individual, may be attributed to any one or more of the following mechanism27.
* Pharmaceutical cause
* Pharmacokinetic cause
* Pharmacodynamic cause
The possible pharmaceutical causes which might be attributed to occurrence of type A adverse drug reaction includes changes in the drug quantity present in a particular product, and also changes in its drug release properties. For examples, there are several reported reactions of gastrointestinal bleeding and hemorrhage due to a rate-controlled preparation of indomethacin. This may be due to irritant effects of high concentrations of indomethacin on a localized area of gastrointestinal mucosa. Another example is the corrosive effects on the esophagus caused are certain doxycycline salts. By changing to another salt, the risk may be reduced dramatically. To avoid such reactions, the drug regulatory authorities have laid down stringent requirements for marketed drug products28.
Alterations in the absorption, distribution, metabolism and elimination of drugs may alter drug effects by changing the concentration of drug present at site of action. The change in the drug effect due to alterations in pharmacokinetics parameters may be experienced as either therapeutic failure or toxicity.
Absorption: Alterations in the rate and extent of drug absorption may result in adverse drug effects. The plasma concentration of drug is partly determined by the rate at which the drug is absorbed after ingestion or injection. The plasma concentration of an orally administered drug in turn depends greatly on the gastric emptying rate. Similarly, the extent of drug absorption (the total amount of drug reaching the general circulation) also plays an important role in altered in response. Following oral administration, many factors may influence the extent of drug absorption including drug formulation, gastrointestinal motility, and first pass metabolism, concomitant administration of other drugs and the absorptive capacity of gastrointestinal mucosa. Any absorption may result in either therapeutic failure or toxicity.
Distribution: There are several factors, which determine in the extent of distribution of a drug including regional blood flow, membrane permeability and protein and tissue binding. Changes in drug distribution may predispose to adverse drug reactions, where the clinical significance of such mechanisms is yet to be proved.
Metabolism: The drug handling capacity of an individual can greatly affects the drug effect. In an individual who has a reduced metabolic rate, accumulation of drug in the body may be higher, leading to increased risk of adverse drug reactions especially type A reaction, while therapeutic failure may occur in an individual who has an enhanced metabolic rate. These changes are due to inter-individual variations in drug metabolizing capacity, which in turn is greatly influenced by genetic, environmental and other factors. For example, slow acetylators are highly prone to develop type A reaction to drugs which are metabolized by acetylation, such as isoniazid, dapsone, hydralazine and procainamide. Also differences in then rate of oxidation by cytochrome P450 system are of clinical importance.
Elimination: The major routes of excretion for many drugs are the kidneys (excretion through urine) and liver (yields metabolites which are then excreted by the kidneys). One of the most important causes of type A adverse drug reaction is a change in the drug elimination rate. Drug accumulation due to reduced elimination may predispose to adverse drug reactions as a result of increased drug concentration in plasma and tissue. Conversely, reduced concentration of drug in plasma and tissue due to enhanced drug elimination may lead to therapeutic failure.
Increased sensitivity of target tissues or organs may predispose a person to adverse drug reactions. The reasons why different individuals react differently to drugs are still not clear, evidence is accumulating to suggest that target tissue or organ sensitivity is influenced by the drug receptors themselves, by homeostatic mechanisms and by disease.
Drug receptors: Most drugs elicit their response by combining with receptors. These receptors are either protein molecules or enzymes. The amount and sensitivity of receptors of an individual may differ from another individual. Some individuals may have fewer specific drug receptors while others may have a higher number of less active receptors. This inter variability between different individuals can greatly affects the drug effect, when the drug acts through these specific receptors.
Homeostatic mechanisms: Many physiological factors may determine the extent of a drug’s effect in an individual as drug affects occur within the environment of the body’s physiological mechanisms. For examples, intravenous atropine produces a variable increase in heart rate and some individuals develop tachycardia of 160 beats per minutes at a dose which is almost ineffective in others. The magnitude of the observed effects is dependent on the balance between parasympathetic and sympathetic cardiac tone, which appears to be under genetic control.
Disease: The pharmacological effects of a drug which are not apparent in a healthy individual may be unmasked by intercurrent diseases. An example is an asthmatic patient who develops bronchoconstriction while taking non-selective beta-blockers such as propranolol.
Mechanism of type B ADRs
The type B adverse drug reactions are aberrant in terms of the normal pharmacology of the drug and they are a heterogeneous group of unpredictable adverse effects. By definition, type B reactions are unrelated to the pharmacology. The major sources for type B reactions includes decomposition of the active ingredient, the effects of the non-drug excipients (additives, preservatives, coloring and solubilising agents) and synthetic byproducts of active constituents. In the majority of cases the use of decomposed drug products may result in therapeutic failure. In some instances, though not all, the decomposed product may be highly toxic and lethal. Deaths have been reported due to decomposition of paraldehyde and its subsequent oxidation to acetic acid. There is a clear recognition of adverse drug reaction caused by excipients. Many additives including propylene glycol and carboxymethylcellulose may cause hypersensitivity reactions. The eosinophilia myalgia syndrome associated with L-tryptophan may be related to the use of preparations containing a contaminant, although a genetic factor may also be involved1,4, 29.
The metabolism of a drug to unusual reactive metabolites may give rise to type B reactions either by a direct or though an immune mediated mechanism. Examples of such reactions include phenacetin-induced methemoglobinemia and carbamazepine induced hypersensitivity reactions. Individuals whose specific bio-inactivation pathways are either more active or less active and with immunological characteristics which render them highly responsive to immunogens and haptogens are more susceptible. The reasons for the occurrence of type B reactions in a particulars individual are not clear30.
The importance of reporting ADR
Not all the hazards can be known before a medicine is marketed. Patient’s consumers and indeed some healthcare professionals may have expectations that medicinal products available are “safe” and may be surprised when regulatory action is taken to restrict the use or withdraw medicines as a result of previously unrecognized safety concerns. Information collected during the pre-marketing phase of medicinal products is inevitably incomplete with regard to complete safety profile of a product because
* Animal testing is insufficiently predictive of human safety
* Data from clinical trials is limited by their size and duration
* Patients in clinical trials are selected and the conditions of use differ from those in clinical practice
* Informations are rare but serious adverse reactions, chronic toxicity, and use in special groups such as pediatrics, geriatrics and in pregnancy) or drug interactions is often incomplete or not available and will only manifest after drug is released, may be after several years.
The effects of ADRs
All medicines have the potential to cause ADRs. Prevention of ADRs helps in order to minimize the harmful effects resulting from ADRS, harmful effects includes
* ADRs are estimated that 2-6% of all admissions to hospitals are due to ADRs
* ADRs contribute to an increased attendance to primary care and may complicate hospital in-patient stay in as many as 10% to 20% of patients
* ADRs may be responsible for deaths (Possibly as high as the 4th commonest cause of death)
* ADRs may increase the length of hospital stay and increase the cost of patient care
* ADRs may adversely affect patient quality of life and may cause patients to lose confidence in doctors
* ADRs may also mimic disease and result in unnecessary investigations and/or delay in treatment.
* ADRs are a major economic burden.
* Occurrence of toxicity in a minority of patients might preclude use of the drug in the majority of patients, if risk factors cannot be identified and appropriate regulatory measures implemented.
Pre marketing studies
The safeties of new medicines are tested in animal models. A great deal of risk information may be obtained from such tests, for examples the level of acute toxicity, which organs will be affected in case of toxicity and dose dependency of such tissue injuries. Specific animal tests for carcinogenicity, teratogenicity and mutogenicity are also available. Animals can only serve as approximately models for humans. We do not have sufficient knowledge to extrapolate information collected from animal studies directly into risks in humans. The predictive value of the different animals tests do not reveal particularly worrying results, safety tests precede onto testing in humans in clinical trial programs.
Clinical trials are carried out in three different phases prior to the submission of a marketing authorization application, with a stepwise increase in the number of individuals being exposed. Prior to the general release of a new product, not more than 4000 individuals have normally been exposed to the new drug. This implies that clinical trials, normally, only have the power to identify adverse reactions of a frequency greater that 0.5-1.0 percent. Clinical trial programs are designed to maximize the chance of demonstrating a therapeutic effect in relation to a control group. Children and the elderly are normally actively excluded from the studies. Once the drug is used in clinical practice, children and elderly, and patients with much more complicated diseases situations can be treated. For cost reasons clinical trials often have a very short duration, which means they cannot generate information about long term adverse effects31-34.
The consequence of the above is that at the time of general marketing of a new medicine, only the most common, dose related (type A) adverse reactions will be known.
The most sensitive, powerful and cost effective system for identification of unknown drug related risks are spontaneous adverse reaction reporting. Every healthcare practitioner should see it as a part if his/her professional duty unexpectedly causing a risk situation for a patient under his/her cares. Pharmacovigilance should not be limited to the reporting of classical adverse effects. It should also be concerned with identification of product defects, unexpected insufficient therapeutic effects, intoxications and misuse abuse situation.
An important outcome of spontaneous adverse reaction reporting programs is the creation of signals of previously unknown or insufficiently documented problems. To verify the hypothesis of a causal link between drug exposure and an adverse outcome, it may be necessary to employ epidemiological techniques. With such techniques it is also possible to quantify the risk which is not possible through spontaneous reporting.
The two epidemiological methods that are most commonly used are cohort studies and case-control studies. In Cohort studies, patient exposed to a particular drug are followed up regularly and adverse reactions in them are compared to a matched control population. Case-control studies involve studying patients who have been affected by an adverse reactions and linking it with drug used prior to the reaction. Case control studies are particularly useful for the study of rare adverse reactions5.
In the hospital setup, healthcare professionals should be very vigilant in detecting ADRs. The possibility of an ADR should always be considered during differential diagnosis. ADRs may be detected during wards rounds with the medical team or during review of the patient’s chart. Patient counseling, medication history interview and communicating with other healthcare professionals may provide additional clues which may be useful in the detection of ADRs7.
To assist the detection of ADRs, healthcare professionals should closely monitor patients who are at risk. These includes
* Patients with renal or hepatic impairment
* Patient taking drugs which have potential to cause ADRs
* Patients who have had previous allergic reactions
* Patients taking multiple drugs
The first step in the detection of ADRs is collection of data. The data to be collected includes patient’s demographic data, presenting complaints, past medication history, drug therapy details including over the counter drugs, current medications and medication on admission, and lab data such as hematological, renal and hepatic function test. Details of the suspected adverse reaction such as time of onset and duration of reaction, nature and severity of reaction, details of the suspected drugs including dose, frequency, time of administration, duration of treatment, plasma concentration of drug, previous report on reported reaction, data on any other causes including risk factors and predisposing factors are useful11.
All the above stated relevant data can be obtained from the following sources of information
* Patient’s case notes and treatment chart
* Patient interview
* Laboratory data sources
Communication with other healthcare professionals
6. Method of Pharmacovigilance
a. Passive Surveillance
A spontaneous report is an unsolicited communication by health care professionals or consumers to a company, regulatory authority or other organization (e.g., WHO, Regional Centers, Poison Control Centre) that describes one or more adverse drug reactions in a patient who was given one or more medicinal products and that does not derive from a study or any organized data collection scheme.
Spontaneous reports play a major role in the identification of safety signals once a drug is marketed. In many instances, a company can be alerted to rare adverse events that were not detected in earlier clinical trials or other pre-marketing studies1-5.
Spontaneous reporting systems; yellow card scheme
The yellow card scheme was established in 1964 as a result of the thalidomide tragedy. Since then, the system has become one of the major international pharmacovigilance resources. The yellow card scheme is run jointly by the MCA (the regulatory agency) and the CSM (an expert advisorycommittee to the MCA).Since 1991, the yellow card scheme has been enhanced by a new computer system, the ADROIT (Adverse Drug Reaction Online Information Tracking) system. ADROIT is different from other databases. Not only does it store the details of the report, but also the image of the yellow card in the optical system. Multiple users can view any yellow card on screen at the same time. The MCA receives approximately 20,000 yellow cards each year. The reports are prioritized so that serious adverse drug reactions receive early attention. The yellow cards are classified into seven priorities by a member of the scientific staff according to the drugs and the nature of the ADR. Priority 1 reports receive the earliest attention
Fig. 3: Adverse drug reaction online information tracking and yellow card system
Sources of data
Fig. 4: Different sources of data for Pharmacovigilance
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Systematic Methods for the Evaluation of Spontaneous Reports
More recently, systematic methods for the detection of safety signals from spontaneous reports have been used. These methods include the calculation of the proportional reporting ratio, as well as the use of Bayesian and other techniques for signal detection. Data mining techniques have also been used to examine drug-drug interactions. Data mining techniques should always be used in conjunction with, and not in place of, analyses of single case reports. Data mining techniques facilitate the evaluation of spontaneous reports by using statistical methods to detect potential signals for further evaluation. This tool does not quantify the magnitude of risk, and caution should be exercised when comparing drugs. Further, when using data mining techniques, consideration should be given to the threshold established for detecting signals; since this will have implications for the sensitivity and specificity of the method (a high threshold is associated with high specificity and low sensitivity). Confounding factors that influence spontaneous adverse event reporting are not removed by data mining. Results of data mining should be interpreted with the knowledge of the weaknesses of the spontaneous reporting system and, more specifically, the large differences in the ADR reporting rate among different drugs and the many potential biases inherent in spontaneous reporting. All signals should be evaluated recognizing the possibility of false positives. In addition, the absence of a signal does not mean that a problem does not exist.
Series of case reports can provide evidence of an association between a drug and an adverse event, but they are generally more useful for generating hypotheses than for verifying an association between drug exposure and outcome. There are certain dis