Managing ADRs and interactions

Question 1

Define drug interactions

Answer 1

An interaction occurring when the effects of one drug are changed by another drug, food, drink or an environmental chemical agent

Question 2

Incidence of drug interactions are proportional to/increased by (8):

Answer 2

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

Question 3

Drug interactions- vaguely describe 3 types of patient outcomes

Answer 3

Adverse and undesirable: toxicity or reduced efficiency
Beneficial: additive effect
Not clinically significant

Question 4

Pharmacokinetic interactions: absorption

Answer 4

Rate and extent of absorption effected

Question 5

Pharmacokinetic interactions: Distribution

Answer 5

Protein binding: Free drug and bound drug affects displacement interactions

Question 6

Pharmacokinetic interactions: metabolic

Answer 6

enzyme induction- decreases levels

enzyme inhibition- increases levels

Question 7

Enzyme inducers

Answer 7

Rifampicin
Phenytoin
Carbamazepine 
Phenobarbitone
St John's Wort
etc

Question 8

Enzyme inhibitors

Answer 8

Amiodarone
Erythromycin
Grapefruit juice
Ketoconazole
Cimetidine
etc

Question 9

Narrow therapeutic index drugs

Answer 9

Warfarin
Digoxin
Ciclosporin
Phenytoin
Carbamazepine
Theophylline 
etc

Question 10

Three types of pharmacodynamic interactions and examples of them

Answer 10

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

Question 11

By what way does food impact drug absorption?

Grape fruit juice increases the levels of which drug?

Answer 11

By effecting GI motility or drug binding!

Felodipine

Question 12

(drug-alcohol)
Alcohol has an additive effect when given with what kind of drugs?
Alcohol has a disulfiram-like effect when given with..?

Answer 12

a) CNS depressants/ drugs with sedating effects

b) metronidazole

Question 13

Name four routes a pharmacist could take when there is a drug interaction

Answer 13

1) avoid the combination
2) adjust the dose
3) monitor the patient
4) continue the medication as before

Question 14

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)

Answer 14

a) amlodipine
amiodarone
fibrates
verapamil
diltiazem

b) reduce dose of simvastatin

Question 15

three ways to monitor patients

Answer 15

1) clinical monitoring eg bp
2) measure drug levels
3) measure markers for interactions eg.INR

Question 16

What is an adverse drug reaction?

3 parts

Answer 16

An Unwanted or harmful reaction experienced following administration of a drug or a combo of drugs and is related to the drug

Question 17

identify 5 patients at risk of ADR’s

Answer 17

Extremes of age
Females
Polypharmacy
Incurrent diseases
History of intolerance or hypersensitivity

Question 18

6 ways to minimise GI damage from NSAIDs

Answer 18

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

Question 19

4 warfarin ADR’s

Answer 19

GI Bleeding
Haematuria
high INR
Haematoma

(they also have a yellow card)

Question 20

When prescribing or dispensing opioids, practitioner should:

Answer 20

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

Question 21

Signs of Digoxin toxicity (4)

Answer 21

Nausea, visual disturbances, heart block, arrhythmia

Question 22

Digoxin toxicity management (5)

Answer 22

stop digoxin
check plasma levels
Check urea & electrolyte levels
Monitor HR and pulse
Check for interactions