High Risk Drugs Flashcards
Amiodarone
- What is the half life?
- What is the dosing regimen?
50 days - clinical effects and side effects may be present for a few months after discontinuation
200mg TDS 7 days
200mg BD 7 days
200mg OD thereafter
Amiodarone
What are the monitoring requirements?
Thyroid function test: before treatment then 6 monthly (T4, T3 and TSH)
Liver function tests: before treatment and then 6 monthly
Serum K+: before treatment
Chest x-ray: before treatment
Annual eye test
High risk of bradycardia with anti hepatitis meds - monitor, monitor ECG if given IV
Amiodarone
Contra-indications?
Severe hypotension
Heart block
Active thyroid disease
Amiodarone
Side effects?
Eyes:
- Corneal micro-deposits - night time glares driving
- Optic neuropathy - stop if vision impaired
Skin:
- Phototoxicity - wear SPF during and for 2-3 months after
- slate grey skin
Thyroid: hypo and hyper (withdraw if possible)
Lungs:
- pneumonitis (dry cough)
- pulmonary fibrosis (shortness of breath)
Hepatotoxicity:
- report jaundice, abdo pain, itching, bruising etc
also causes peripheral neuropathy (reversible), AV block/bradycardia, N+V and taste disturbance
Amiodarone
Common interactions outcomes?
Amiodarone is an enzyme INHIBITOR
QT prolongation risk increased
Risk of bradycardia, AV block and myocardial depression
Increased risk of myopathy with statins
(max simvastatin 20mg)
Amiodarone is an enzyme INHIBITOR
Which drugs have subsequent interactions?
Increases the effect of warfarin, phenytoin and digoxin (must HALVE digoxin dose) most notably
Also increases levels of dabigatran and flecainide
Amiodarone increases the risk of QT prolongation
Which drugs subsequently interact?
Antipsychotics - especially sulpiride (1), amisulpiride(2), pimozide(1) and haloperidol(1)
Quinolones (moxifloxacin)
Hydroxychloroquine, chloroquine, mefloquine, quinine
SSRIs (escitalopram/citalopram), TCAs, venlafaxine
Macrolides
Tolterodine (urinary frequency)
Lithium
Methadone, apomorphine
5HT-3 antagonists, domperidone
Amiodarone increases the risk of bradycardia, AV block and myocardial depression with which drugs?
Beta blockers
Rate limiting CCBs (diltiazem and verapamil)
ACEi and ARBs
Monitoring requirements?
Blood pressure
Renal function and serum electrolytes
1-2 weeks after starting and 1-2 weeks after dose increase
ACEi and ARBs
Side effects?
Dry cough - switch to ARB
Hyperkalaemia
Anaphylactoid reactions - angioedema
Renal impairment
- nephrotoxic (DAMN drug)
- abnormal renal function (renal artery stenosis - can give in unilateral but not bilateral)
- AKI (anuria, confusion, dehydration, N+V)
Note - renoprotective in CKD
Hypotension - give first dose at bedtime
Hepatotoxicity - cholestatic jaundice (ALT 3x ULN)
HypOglycaemia, mouth ulcers and taste disturbance
ACEi and ARBs
Interactions?
Increases plasma LITHIUM concentration
Hyperkalaemia - Aliskeren, K+ sparing diuretic and aldosterone antagonists
Nephrotoxicity - NSAIDs, aliskeren
Hypotension - diuretics
Digoxin
Therapeutic range and mechanism of action
0.7 mcg/L - 2 mcg/L
cardiac glycoside that increases the force of contraction (positive inotrope) and decreases conductivity in the AV node (negative chronotrope)
Digoxin
Monitoring?
Monitor serum electrolytes (K+, Mg2+, Ca2+) - hypOkalaemia, hypOmagnesaemia and hypERcalcaemia can potentiate toxicity (hypoxia also increases risk)
Renal function - toxicity risk increases when eGFR falls
Routine plasma monitoring is not required unless toxicity is suspected or there is renal impairment
Plasma level should be taken 6 hours post dose
Digoxin
Doses in atrial flutter and non-paroxysmal AF?
Doses in severe heart failure?
Atrial flutter/AF = 125 - 250mcg
Heart failure = 62.5 - 125mcg
Loading doses required due to long t1/2
Note: elixer (75%), tablet (90%), IV (100%)
Digoxin
Signs of toxicity?
SLOW AND SICK
- Bradycardia/heart block
- GI effects: N+V, abdominal pain, diarrhoea
- Visual disturbances: blurred or yellow vision
- Confusion or delirium
- Rash
Risk of toxicity in hypoK, hypoMg, hyperCa, hypoxia and renal impairment
Digoxin
Management of toxicity?
Withdraw digoxin
Give digoxin specific antibody for life-threatening arrhythmias unresponsive to atropine
Digoxin
Interactions?
Drugs that cause hypokalaemia (predisposes to toxicity)
Diuretics (loop/thiazide), B2 agonist, steroids, theophylline (give K+ or K+ sparing diuretics)
Enzyme inhibitors (toxicity) Amiodarone (HALVE digoxin dose), rate limiting CCBs, macrolides, ciclosporin
Enzyme inducers (subtherapeutic treatement) St Johns wort, rifampicin
Drugs that reduce renal clearance (toxicity)
NSAIDS, ACEi/ARBs
Digoxin
Interaction acronym?
Hint: CRASED
CRASED
C - calcium channel blockers (verapamil) R - rifampicin A - amiodarone (half dose) S - st johns wort E - erythromycin D - diuretics