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
