High risk drugs Flashcards
Loading Dose of amiodarone
200mg TDS for 7 days, then 200mg bd for 7 days
Maintenance dose amiodarone
200mg
Side effects of amiodarone
Bradycardia/blue Interstitial lung disease Thyroid Corneal/cutaneous Hepatic/hypotension
Monitoring of amiodarone before
TFTs
Serum potassium
Chest xray
Monitoring on amiodarone
LFTS
TFTs every 6 months
eCG
Symptoms can continue for several weeks after discontinuation
Warfarin and amiodarone
Increased anticoagulant effect of warfarin
Beta blockers and amiodarone
Increased risk of bradycardia, AV block and myocardial depression
Amiodarone and lithium
Risk of ventricular arrhythmias
Amiodarone and digoxin
Increased digoxin concentration
Digoxin mechanism
cardiac glycoside
Increases myocardial contraction and reduces conductivity in AV node
Optimum plasma concentration digoxin
1-2 mcg/L
1.5-3 indicates toxicity
Digoxin monitoring
serum electrolytes esp potassium
renal function
Toxicity of digoxin
Made worse by hypokalaemia
Managed by giving potassium sparing diuretic
Digoxin side effects
Nausea and vomiting
Blurred or yellow vision
Confusion or delirium
Digoxin and erythromycin
Increased digoxin concentration
Digoxin and rifampicin
Reduced digoxin concentration
Digoxin and St John’s Wort
Reduced digoxin concentration
Digoxin and diuretics
Increased toxicity of digoxin if hypokalaemia occurs with loops and thiazides
Digoxin and CCBs
Increased digoxin concentration
Lithium serum concentration
0.4-1 mmol/L
Above 1.5mmol/L fatal/toxic
Lithium toxicity
Levels Increased urination Tremor and thirst Hair thinning and hypothyroidism Interactions Upset stomach Muscle weakness Skin effect - acne or psoriasis
Lithium monitoring
Lithium conc every 3 months
U&Es and TFTs every 6-12 months
Maintain sodium concentrations
Lithium counselling
Maintain adequate fluid intake
Avoid dietary changes with sodium
Lithium and ACE inhibitors
Excretion of lithium reduced by ACE inhibitors – Risk of lithium toxicity
Lithium and NSAIDS
Excretion of lithium reduced by NSAIDS – Risk of lithium toxicity
Lithium and diuretics
Excretion of lithium reduced
Toxic signs of methotrexate
Blood dyscraisas
Liver toxicity
Pulmonary toxicity
Monitoring of methotrexate
LFTS
U&es before starting
Dose of methotrexate
7.5mg once weekly
Max weekly dose of 20mg
Methotrexate and NSAIDS
Monitor dose of methotrexate as dose can be increased
Avoid OTC preparations
Methotrexate and folic acid
5mg folic acid to prevent methotrexate-induced mucositis or myelosuppression
Side effects of methotrexate
GI bleeding and ulceration
Hepatotoxicity
Indication of phenytoin
Epilepsy (all except absence) and neuropathic pain
Phenytoin concentration
10-20mg/L
Small dose may increase plasma conc excessively
Phenytoin monitoring
FBC and LFTs
Phenytoin side effects
P450 interactions Hirsuitism Enlarged gums Nystagmus Yellow staining of skin Teratogenicity Osteomalacia interfere with B12 metabolism Neuropathies
Phenytoin counselling
Blood dyscraisa
Skin disorders
Take with or after food
Phenytoin and NSAIDS
Effect of phenytoin enhanced
Phenytoin and wafarin
Accelerates metabolism of wafarin
Phenytoin and cimetidine
Inhibits metabolism of phenytoin
Phenytoin and fluoxetine
Increased concentration of phenytoin
Phenytoin and st johns wort
Reduced plasma conc of phenytoin
Phenytoin and NSAIDS
Effects enhanced by NSAIDS
Plasma concentration of theophylline
10-20mg/L
Theophylline side effects
Tremor Heart arrhythmias Electrolyte imbalance- hypokalaemia Oxidase inhibitor Pain in abdomen Heachaches, insomnia and seizures
Theophylline monitoring
Plasma theophylline conc
Lung function test
serum potassium
Theophylline and quinolones
Increased risk of convulsions
Theophylline and St Johns wort
Plasma conc of theophylline reduced
Theophylline and rifampicin
Plasma conc of theophylline reduced
Theophylline and cimetidine
Plasma conc of theophylline increased
Theophylline and fluconazole
Plasma conc of theophylline reduced
Warfarin loading dose
10mg
Warfarin side effects
Haemorrhage Rash Bruising Bleeding Alopecia Unexplained drop in haematocrit Skin necrosis Purple toes jaundice hepatic toxicity
Warfarin counselling
Avoid dietary changes
Same time each day
Report bleeding etc
Warfarin and NSAIDS
Enhanced anticoagulation
Wafarin and fluconazole
Enhanced anticoagulation
Wafarin and statins
Enhanced anticoagulation
Wafarin and cipro/metronidazole/ clarithromycin
Enhanced anticoagulation
Wafarin and griseofulvin
reduced anticoagulation
warfarin and antiepileptic
reduced anticoagulation
warfarin and alcohol
Dependent on consumption
warfarin and cranberry juice
Enhanced anticoagulation
wafarin and vitamin K
anticoagulant effect antagonised by vit k