Adverse Drug Reactions | Causes and Prevention | Roles of Pharmacists

More than 10 percent of the hospitalised patients are due to Adverse drug reactions (ADRs) which accounts for several thousands of deaths yearly; being 4th to 6th cause of death in USA.(1)

what is Adverse Drug Reaction?

National agency for food and drug administration and control (NAFDAC) defines Adverse Drug Reactions (ADRs) as A response to a medicine which is noxious (harmful) and unintended and which occurs at doses normally used in man for the prophylaxis (prevention), diagnosis or therapy (treatment) of diseases, or for the modification of physiological function’.

Therefore, for a drug effect to be tagged as Adverse drug reaction, it must have the following characteristics.

  • It must be harmful or noxious to health.
  • The effect is uintended
  • Dose used is normal

Relationship between Adverse Drug Reactions (ADR) and DTPs

Adverse drug reactions is one among the 8 classes of Drug therapy problems. It is a Drug Therapy Problem because it is an undesired outcome in a drug therapy.

Nevertheless, it is the only DTP that occurs with little or no contribution from the Physician. According to Tanzania Food and drug authority (2) “ADR is an unexpected consequence of drug usage and its risk of occurrence can not be predetermined”.

Almost all effective drugs, no matter how skillfully used, may cause adverse reactions. The fact that an adverse reaction has occurred does not reflect in any way discreditably on the health care professional who prescribed, dispensed or sold the drug.

Difference between ADR and side effects

Adverse drug reactions

The knowledge of the mechanism of actions of drugs makes it easier to predict a side effect unlike an adverse effect which happens without warning. E.g., Side effects like slowing of heart beat or shortness of breathe will occur while using Cholinergic drugs since they enhance the actions of acetylcholine and the parasympathetic system.

ADR usually occurs when there is an incomplete or malfunctioning of the metabolism or the elimination mechanism (pharmacokinetics) while side effects occurs at pharmacodynamic level. However, pharmacokinectic properties of a drug can also superimpose the clinical side effects of a drug.

ADR of any drug is usually rare, it occurs to below 1% of the population (e.g., the Stephen Johnson syndrome associated with cotrimoxazole) while side effects occurs to greater than 50% of the population.

Causes of Adverse drug reactions

• Dose related ADRs

This type of ADR occurs as a result of high dose of the drug in the system due to insufficient elimination or metabolism mechanism. Drug-drug interaction and Drug-disease interaction ( especially one that has to do with renal or hepatic impairment) falls under this category.

• Allergic ADRs

Allergic ADRs occurs when drugs are acts as an immunogen or an antigen to the patients immune system. after first exposure, sensitization to the drug occurs and subsequent build of antibodies against the drug.

On subsequent exposure, serious hypersensitive reaction occurs e.g., hypersentivity reaction of Abacavir to some patients.(3)

• Idiosyncratic ADRs

Idiosyncratic ADRs is neither dose related nor allergic, it defines reactions that have no defined cause. However, most Idiosyncratic ADRs occurs as a genetically predispositions. Meaning, it occurs to few individuals due to presence or absence of some genetic components. E.g., the reaction of slow and fast acetylators to some drugs like Isoniazid, hydralazine and Procainamide. (4)

Role of a pharmacist in preventing Adverse drug reactions

The Pharmacist as the last gateway to ensuring the patient gets the best outcome of his drug. It is his duty to check medication appropriateness, performing medication reconciliation, medication reviews, developing a care plan and monitoring patients.(5)

Meanwhile, people do refer to Adverse drug reactions to be ‘side effects’ which impinges on pharmacovigillance and proper diagnosis. Good safety monitoring encourages healthcare practitioners to take fuller responsibility for the medicines they use. It improves clinical effectiveness and increases the confidence with which they and their patients use medicines. (6)

Tips for reducing Adverse drug reactions

  1. There is always the need for the Pharmacist to assess patients Prescription for appropriate indication, safety, efficacy and also possible drug interactions.
  2. It is the duty of a pharmacist to educate patients about  possible side effects or drug therapy problems that may arise from using their medications and what to do if any comes up.(7)
  3. Good Pharmacy Communication skills will enable the patient be part of the team. Therefore,information on the side effects of the drug can easily be related to the Pharmacists for proper action.(8)
  4. The pharmacist should monitor and address issues of Polypharmacy especially in the elderly, which may give rise to uncontrollable drug interactions and non-adherence.(9)
  5. Integration of Precription drug monitoring programmes (PDMPs) into pharmacy database to track the prescription and dispensing of harmful controlled drugs by pharmacists such as Opiods.(10)
  6. Pharmacists through pharmacovigillance or proper documentation of adverse drug reactions can provide data for research tools to determine the effective ways of using a medicinal agent(11)

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