Health Canada: Adverse reactions are undesirable effects to health products (including drugs, medical devices and natural health products).
WHO: any noxious and unintended response to a medicinal product.
Why are ADRs so important?
Common:
- 30% of hospitalized patients will experience an ADR.
- 2-5% of all admissions due to an ADR.
Expensive:
- A study in UK suggest ADRs cause about 6.5% of all admissions, costing the UK health system $847 million per annum (BMJ 2004;329:15-19).
- ADRs cause an average 2 day increase in hospital stays.
Serious:
- Serious/fatal reactions are between the 4th and 6th leading cause
- of death (JAMA 1998;279:200-5).
Often preventable.
Risk factors for the development of an ADR include:
- Predictable reactions.
- Drug-drug interactions.
- Is the dose appropriate for hepatic/renal function?
- Female gender.
- The greater the number of medications administered, the greater the risk of developing an ADR.
- Elderly.
Use a systematic approach when evaluating patients with potential ADRs:
- Clinical diagnosis
- Analysis of drug exposure
- Taking accurate drug history, including OTC and herbal medications, is essential
- Differential diagnosis
- Literature search
- Treat the patient
- Confirmation (or testing)
- Advice to patient
- Reporting
Treatment Options:
Discontinue the possible offending agent if:
- It can be safely stopped.
- The event is life-threatening or intolerable.
- There is a reasonable alternative.
- Continuing the medication will further exacerbate the patient’s condition.
Continue the medication (modified as needed) if:
- It is medically necessary.
- There is no reasonable alternative.
- The problem is mild and will resolve.
Administer appropriate treatment:
- e.g., dextrose, antihistamines, epinephrine, naloxone, corticosteroids,
glucagon.
Provide supportive or palliative care:
- e.g., hydration, corticosteroids, analgesics or antipruritics.
Consider rechallenge or desensitization.
Note: Fever is a predictor of a more serious drug reaction.
DRESS?
DRESS = drug reaction eosinophilia systemic.
Symptoms:
- Fever, skin eruption and internal organ involvement (+ eosinophilia).
Generally occurs on first exposure to the drug, with initial symptoms starting 1-8 weeks after starting medication.
Rare reaction: occurs in approximately 1 in 10000 patients.
Genetic factors might play a role.
Specific drug classes that are associated with DRESS include:
- Anticonvulsants :phenytoin, phenobarbital, carbamazepine and lamotrigine.
- Antimicrobials: sulfonamide antimicrobials, nitrofurantoin and minocycline.
- Anti-retrovirals.
- Allopurinol.
Allergy 2010;65:1357-66
Immunol Allergy Clin N Am 2004;24:425-43
Read also: Tips for Effective Pharmacovigilance Reporting of Adverse Events
Resource Person: Lobna Adi