Prescribing Flashcards
Benefits
BNF - licensed use and benefits
Risks
Prevent Classify - dose dependence + time dependence Diagnose - identify T R
Adverse reactions
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
Drugs causing hepatitis/necrosis
- dose dependent
- dose independent
INCREASE in ALT
Dose dependent
-paracetamol OD
-Aspirin
Dose independent in susceptible patients
- isoniazid, pyrazinamide
- valproate
- methyldopa
- NSAIDs
- phenytoins
- statins
Drugs causing cholestasis
- dose dependent
- dose independent
Increase in AST, Bilirubin
Dose dependent
-rifampicin
-estrogen+anabolic steroids
Dose independent - start with chlo
Drugs causing steatosis
- microvascular
- macrovascular and cirrhosis
Microvesicular far (VAT) = Reye’s syndrome
- valproate
- aspirin
- tetracycline
Macrovesicular fat and cirrhosis
- alcoholic hepatitis
- amiodarone
- methotrexate
Time dependent ADRs
- rapid reaction
- first dose
- intermediate risk (risk increases at first but decreases)
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) =>
Time independent ADRs
-can occur any time during therapy
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
Signs of cardiotoxicity
5 lows
-K, Mg, pH, pO2, fT4
1 high
-Ca2
ADRs’ pharmacovigilance spontaneous reporting
Electronic Yellow Card
Report any suspected
Risks - Interactions
May be synergistic, antagonistic
Pharmacokinetics - what body does to drug
-ADME
Pharmacodynamic - what drug does to body
What decrease GI motility
What increases GI motility
Chelation
Decrease => alter rate of absorption
- opioids
- antimuscarinincs (TCAs)
Increase =>
-metoclopromide
Chelation by antacids
Displacement, distribution
Displacement from plasma proteins
Metabolism
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
Narrow therapeutic range
WAC STOPS warfarin antiarrythmics cicloprorin sulphonylureas Theophyllines oral contraceptive pill phenytoin steroids, statins
PK interactions in warfarin
Protein binding displacement
Inhibit metabolism
Induction of metabolism
Excretion
Glomerular filtration - unbound free active drug only
Active tubular secretion - ability decreased in renal failure
Passie tubular reabsorption
Necessary prophylaxis
NSAIDS + PPIs
Opioids + laxatives, antiemetics
CS + alendronate
Susceptibilities
A SAD GAP allergy sex age disease genetic altered physiology pregnancy, breast feeding
Penicilin based names
Amoxicillin
Augumentin/coamoxiclav
Tazocin
Sex susceptibility
Women
- alcohol
- ACEi
- drug induced lupus
- hepatitis
Age susceptibility
ws
