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Pharmacists graduating today who are just beginning their careers most often just use the, Lecture notes of Clinical Medicine

The predisposing factors that increase the risk of adverse drug reactions (ADRs) in patients, including polypharmacy, multiple and intercurrent diseases, age, drug characteristics, gender, race, and genetic factors. It also covers the detection and monitoring of ADRs through pre-marketing studies, clinical trials, and post-marketing surveillance. The document emphasizes the importance of identifying and managing ADRs to improve patient safety and outcomes.

Typology: Lecture notes

2021/2022

Available from 02/19/2023

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ADR management
Predisposing Factors:
Polypharmacy:
Patients on multiple drug therapy are more prone to develop an ADR 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 with an
increase in the number of drugs administered.
Multiple and intercurrent diseases:
Patients with multiple diseases are at increased risk of developing an ADR due to
multiple drug use for their diseases.
Similarly, patients with impaired hepatic or renal status are also at 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
aminoglycosides is at increased risk of developing nephrotoxicity unless
appropriate dose adjustments are made.
Age:
Elderly and pediatric patients are more vulnerable to ADRs. Elderly patients are
more susceptible to ADRs due to the physiological changes (pharmacokinetic
and pharmacodynamic) which accompany ageing, and also because they often
take many drugs for chronic and multiple diseases.
Drug characteristics:
Some drugs are highly toxic in nature and patients who are treated with these
agents are at an increased risk of ADRs. For example, nausea and vomiting is a
common ADR seen in patients treated with cytotoxic anti-cancer drugs.
Also, patients who are treated with drugs which have a narrow therapeutic
range such as digoxin and gentamicin are more susceptible, as a slight increase
in the serum concentration of these drugs may result in toxicity.
Gender:
Women are reported to be more susceptible to ADRs than men, for a number of
reasons: physiological,pharmacokinetic, pharmacodynamic and hormonal.
Chloramphenicol-induced aplastic anemia and phenylbutazone-induced
agranulocytosis are twice and thrice as common in women as in men,
respectively.
Race and genetic factors:
It is evident that ADRs are more common in genetically predisposed individuals.
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ADR management

Predisposing Factors:

Polypharmacy:  Patients on multiple drug therapy are more prone to develop an ADR 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 with an increase in the number of drugs administered. Multiple and intercurrent diseases:  Patients with multiple diseases are at increased risk of developing an ADR due to multiple drug use for their diseases.  Similarly, patients with impaired hepatic or renal status are also at 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 aminoglycosides is at increased risk of developing nephrotoxicity unless appropriate dose adjustments are made.

Age:

 Elderly and pediatric patients are more vulnerable to ADRs. Elderly patients are more susceptible to ADRs due to the physiological changes (pharmacokinetic and pharmacodynamic) which accompany ageing, and also because they often take many drugs for chronic and multiple diseases.

Drug characteristics:

 Some drugs are highly toxic in nature and patients who are treated with these agents are at an increased risk of ADRs. For example, nausea and vomiting is a common ADR seen in patients treated with cytotoxic anti-cancer drugs.  Also, patients who are treated with drugs which have a narrow therapeutic range such as digoxin and gentamicin are more susceptible, as a slight increase in the serum concentration of these drugs may result in toxicity.

Gender:

 Women are reported to be more susceptible to ADRs than men, for a number of reasons: physiological,pharmacokinetic, pharmacodynamic and hormonal.  Chloramphenicol-induced aplastic anemia and phenylbutazone-induced agranulocytosis are twice and thrice as common in women as in men, respectively.

Race and genetic factors:

 It is evident that ADRs are more common in genetically predisposed individuals.

 For example,patients who are deficient in glucose-6-phosphate dehydrogenase (G6PD) 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.

Detection and Monitoring of ADRs:

1) Pre-marketing studies:  During the development of new medicines, their safety is tested in animal models.  A great deal of risk information may be obtained from such tests, such as the level of acute toxicity, which organs will be affected in case of toxicity and the dose dependency of such tissue injuries.  Specific animal tests for carcinogenicity, teratogenicity and mutagenicity are also available. However, animals can only serveas approximate models for humans.  The predictive value of the different animal tests is in all instances uncertain.  If animal tests do not reveal particularly worrying results, safety tests proceed 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 would have normally been exposed to the new drug, often fewer.  This implies that clinical trials normally only have the power to identify adverse reactions of a frequency greater that 0.5–1.0%.  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.

 Each case is matched with several disease-free control patients randomly recruited from the study base (controls).  Both cases and controls are investigated regarding their exposure to possible causative agents prior to the occurrence of the event.

Under-reporting of ADRs:

1. Under-reporting varies with a number of factors:

2. Reporting is higher for new drugs than for old

3. Serious reactions are reported to a higher degree

4. Type B reactions are reported more commonly than

their share of events in practice

5. Reporting is affected by promotional claims of the

drug sponsor

6. Publicity of a specific drug-related problem triggers

further reporting, not necessarily related to the real

frequency

7. Reporting is affected by general publicity around the

adverse reaction reporting scheme

The reasons given most often by health professionals

for not reporting are:

 Lack of time

 Lack of knowledge on what, how or where to report

 The drug–reaction association is uncertain

 The reaction is already well known

 Guilt or fear of litigation

 Belief that all registered medicines are safe

 Non-availability of reporting forms