Managing ADRs and interactions Flashcards
Define drug interactions
An interaction occurring when the effects of one drug are changed by another drug, food, drink or an environmental chemical agent
Incidence of drug interactions are proportional to/increased by (8):
Age Frailty No. of meds No. of physicians involved in care Other medical conditions (hepatic/renal impairment) OTC use Herbal Meds Family/friends offering meds
Drug interactions- vaguely describe 3 types of patient outcomes
Adverse and undesirable: toxicity or reduced efficiency
Beneficial: additive effect
Not clinically significant
Pharmacokinetic interactions: absorption
Rate and extent of absorption effected
Pharmacokinetic interactions: Distribution
Protein binding: Free drug and bound drug affects displacement interactions
Pharmacokinetic interactions: metabolic
enzyme induction- decreases levels
enzyme inhibition- increases levels
Enzyme inducers
Rifampicin Phenytoin Carbamazepine Phenobarbitone St John's Wort etc
Enzyme inhibitors
Amiodarone Erythromycin Grapefruit juice Ketoconazole Cimetidine etc
Narrow therapeutic index drugs
Warfarin Digoxin Ciclosporin Phenytoin Carbamazepine Theophylline etc
Three types of pharmacodynamic interactions and examples of them
1) Additive (synergistic)- eg. K-sparing diuretics & ACEi
2) Antagonistic (opposing)- eg. BB’s and B2 receptor agonist (salbutamol)
3) Interaction due to electrolyte disturbances - eg. decreased K+ due to loops increases digoxin toxicity
By what way does food impact drug absorption?
Grape fruit juice increases the levels of which drug?
By effecting GI motility or drug binding!
Felodipine
(drug-alcohol)
Alcohol has an additive effect when given with what kind of drugs?
Alcohol has a disulfiram-like effect when given with..?
a) CNS depressants/ drugs with sedating effects
b) metronidazole
Name four routes a pharmacist could take when there is a drug interaction
1) avoid the combination
2) adjust the dose
3) monitor the patient
4) continue the medication as before
Name 5 drugs that increase the risk of myopathy when given with simvastatin
(CLUE: 3 of them are CCBS’s)
What action should you take? (clue: simvastatin)
a) amlodipine amiodarone fibrates verapamil diltiazem
b) reduce dose of simvastatin
three ways to monitor patients
1) clinical monitoring eg bp
2) measure drug levels
3) measure markers for interactions eg.INR
What is an adverse drug reaction?
3 parts
An Unwanted or harmful reaction experienced following administration of a drug or a combo of drugs and is related to the drug
identify 5 patients at risk of ADR’s
Extremes of age Females Polypharmacy Incurrent diseases History of intolerance or hypersensitivity
6 ways to minimise GI damage from NSAIDs
1) paracetamol for analgesia (if applicable)
2) Use Ibuprofen at lowest recommended dose (its low risk)
3) Don’t use more than 1 NSAID at a time
4) Identify patients at risk: elderly, history of ulcers
5) Prophylaxis with PPI (omeprazole)
6) Counselling: take with/after food. label 21
4 warfarin ADR’s
GI Bleeding
Haematuria
high INR
Haematoma
(they also have a yellow card)
When prescribing or dispensing opioids, practitioner should:
1) confirm any recent opioid (dose, form, frequency, other analgesics prescribed)
2) Ensure any dose increase is still safe
3) NOT MORE THAN 50% higher than previous dose
4) ensure patient familiar w. starting dose, frequency of admin, dosing increments, OD symptoms, common S/E
Signs of Digoxin toxicity (4)
Nausea, visual disturbances, heart block, arrhythmia
Digoxin toxicity management (5)
stop digoxin check plasma levels Check urea & electrolyte levels Monitor HR and pulse Check for interactions
