Prescribing

Question 1

Benefits

Answer 1

BNF - licensed use and benefits

Question 2

Risks

Answer 2

Prevent
Classify - dose dependence + time dependence
Diagnose - identify
T
R

Question 3

Adverse reactions

Answer 3

Most reactions are avoidable

• low dose aspirin, NSAIDs, - GI bleeds
• diuretics - dehydration
• warfarin - bleed risk

Dose dependence

• supratherapeutic doses - toxic
• therapeutic dose - side effects
  
  • NSAIDSs - renal failure
  • antidepressant - ACh effecr
  • ACEi - cough
• subtherapeutic dose - hypersusceptibility
  
  • allergy

Question 4

Drugs causing hepatitis/necrosis

• dose dependent
• dose independent

Answer 4

INCREASE in ALT
Dose dependent
-paracetamol OD
-Aspirin

Dose independent in susceptible patients

• isoniazid, pyrazinamide
• valproate
• methyldopa
• NSAIDs
• phenytoins
• statins

Question 5

Drugs causing cholestasis

• dose dependent
• dose independent

Answer 5

Increase in AST, Bilirubin
Dose dependent
-rifampicin
-estrogen+anabolic steroids

Dose independent - start with chlo

Question 6

Drugs causing steatosis

• microvascular
• macrovascular and cirrhosis

Answer 6

Microvesicular far (VAT) = Reye’s syndrome

• valproate
• aspirin
• tetracycline

Macrovesicular fat and cirrhosis

• alcoholic hepatitis
• amiodarone
• methotrexate

Question 7

Time dependent ADRs

• rapid reaction
• first dose
• intermediate risk (risk increases at first but decreases)

Answer 7

Too rapid IV vancomycin => red man syndrome

ACEi first dose => hypotension
Penicilin => hypersensitivity

Carbimazole, 5ASA => sore throat, tiredness, increased bleeding risk

CS => osteoporosis (monitor use, prophylaxis)

Dopamine receptor antagonists => warn, monitor use, prophylaxis

Withdrawal syndromes (opiates, BZ, aHTNs, Bb) => withdraw slowly

Delayed (carcinogens) =>

Question 8

Time independent ADRs

-can occur any time during therapy

Answer 8

Due to change in dose

• companies may change the formulation
• prescribe a given brand to a given patient

Due to change in concentration

• forewarn patient
• monitor, reduce dosage if needed
• avoid interacting drugs

No changes in dose or concentration

• forewarn patient
• monitor U&E
• avoid interacting drugs

Question 9

Signs of cardiotoxicity

Answer 9

5 lows
-K, Mg, pH, pO2, fT4
1 high
-Ca2

Question 10

ADRs’ pharmacovigilance spontaneous reporting

Answer 10

Electronic Yellow Card

Report any suspected

Question 11

Risks - Interactions

Answer 11

May be synergistic, antagonistic
Pharmacokinetics - what body does to drug
-ADME

Pharmacodynamic - what drug does to body

Question 12

What decrease GI motility
What increases GI motility

Chelation

Answer 12

Decrease => alter rate of absorption

• opioids
• antimuscarinincs (TCAs)

Increase =>
-metoclopromide

Chelation by antacids

Question 13

Displacement, distribution

Answer 13

Displacement from plasma proteins

Question 14

Metabolism

Answer 14

Liver enzyme inducers => reduces concentration and activity (PC BRAS)

• phenytoin
• carbamazepine
• barbiturates
• rifampicin
• alcohol
• smoking St Johns Wort

Liver enzyme inhibitors (GO DEVICES)

• grapefruit juice
• omeprazole
• disulfriam
• erythromycin
• valproate
• isoniazid
• cimetidine
• ethanol
• sulphonamides
• allopurinol
• metronidazole, ketoconazole
• ciprofloxacin
• verapamil+diltaizam

Question 15

Narrow therapeutic range

Answer 15

WAC STOPS
warfarin
antiarrythmics
cicloprorin
sulphonylureas
Theophyllines
oral contraceptive pill
phenytoin
steroids, statins

Question 16

PK interactions in warfarin

Answer 16

Protein binding displacement
Inhibit metabolism
Induction of metabolism

Question 17

Excretion

Answer 17

Glomerular filtration - unbound free active drug only
Active tubular secretion - ability decreased in renal failure
Passie tubular reabsorption

Question 18

Necessary prophylaxis

Answer 18

NSAIDS + PPIs
Opioids + laxatives, antiemetics
CS + alendronate

Question 19

Susceptibilities

Answer 19

A SAD GAP
allergy
sex
age
disease
genetic
altered physiology
pregnancy, breast feeding

Question 20

Penicilin based names

Answer 20

Amoxicillin
Augumentin/coamoxiclav
Tazocin

Question 21

Sex susceptibility

Answer 21

Women

• alcohol
• ACEi
• drug induced lupus
• hepatitis

Question 22

Age susceptibility

Answer 22

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