.Class I: membrane stabilising drugs (e.g. lidocaine,
flecainide)
.Class II: beta-blockers
.Class III: amiodarone; sotalol (also Class II)
.Class IV: calcium-channel blockers (includes verapamil
but not dihydropyridines)
The negative inotropic effects of anti-arrhythmic drugs
tend to be additive. Therefore special care should be taken if
two or more are used, especially if myocardial function is
impaired. Most drugs that are effective in countering
arrhythmias can also provoke them in some circumstances;
moreover, hypokalaemia enhances the arrhythmogenic (pro-
arrhythmic) effect of many drugs.
Adenosine is the treatment of choice for terminating
supraventricular tachycardias, including those associated
with accessory conducting pathways (e.g. Wolff-Parkinson-
White syndrome). It is also used in the diagnosis of
supraventricular arrhythmias. It is not negatively inotropic
and does not cause significant hypotension. The injection
should be administered by rapid intravenous injection into a
central or large peripheral vein.
Amiodarone hydrochloride is useful in the management of
both supraventricular and ventricular tachyarrhythmias. It
can be given by intravenous infusion and by mouth, and
causes little or no myocardial depression. Unlike oral
amiodarone hydrochloride, intravenous amiodarone
hydrochloride acts relatively rapidly. Intravenous
amiodarone hydrochloride is also used in cardiopulmonary
resuscitation for ventricularfibrillation or pulseless
ventricular tachycardia unresponsive to d.c. shock.
Amiodarone hydrochloride has a very long half-life
(extending to several weeks) and only needs to be given once
daily (but high doses may cause nausea unless divided).
Many weeks or months may be required to achieve steady
state plasma-amiodarone concentration; this is particularly
important when drug interactions are likely.
Beta-blockersact as anti-arrhythmic drugs principally by
attenuating the effects of the sympathetic system on
automaticity and conductivity within the heart. Sotalol
hydrochloride has a role in the management of ventricular
arrhythmias.
Oral administration of digoxin slows the ventricular rate in
atrialfibrillation and in atrialflutter. However, intravenous
infusion of digoxin is rarely effective for rapid control of
ventricular rate.
Flecainide acetate is useful for the treatment of resistant
re-entry supraventricular tachycardia, ventricular
tachycardia, ventricular ectopic beats, arrhythmias
associated with accessory conducting pathways (e.g. Wolff-
Parkinson- White syndrome), and paroxysmal atrial
fibrillation. Flecainide acetate crosses the placenta and can
be used to control fetal supraventricular arrhythmias.
Lidocaine hydrochloride can be used in cardiopulmonary
resuscitation in children with ventricularfibrillation or
pulseless ventricular tachycardia unresponsive to d.c. shock,
but only if amiodarone hydrochloride is not available. Doses
may need to be reduced in children with persistently poor
cardiac output and hepatic or renal failure.
Verapamil hydrochloride can cause severe haemodynamic
compromise (refractory hypotension and cardiac arrest)
when used for the acute treatment of arrhythmias in
neonates and infants; it is contra-indicated in children under
1 year. It is also contra-indicated in those with congestive
heart failure, syndromes associated with accessory
conducting pathways (e.g. Wolff-Parkinson-White
syndrome) and in most receiving concomitant beta-blockers.
It can be useful in older children with supraventricular
tachycardia.Other drugs used for ArrhythmiasMetoprolol tartrate,
p. 107. Propranolol hydrochloride, p. 104ANTIARRHYTHMICS›CLASS IB
Lidocaine hydrochloride
(Lignocaine hydrochloride)
lINDICATIONS AND DOSE
Ventricular arrhythmias|Pulseless ventricular
tachycardia|Ventricular fibrillation
▶INITIALLY BY INTRAVENOUS INJECTION, OR BY INTRAOSSEOUS
INJECTION
▶Neonate:Initially 0. 5 – 1 mg/kg, followed immediately by
(by intravenous infusion) 0. 6 – 3 mg/kg/hour,
alternatively (by intravenous injection or by
intraosseous injection) 0. 5 – 1 mg/kg repeated at
intervals of not less than 5 minutes if infusion is not
immediately available following initial injection, until
infusion can be initiated; maximum 3 mg/kg per course.▶Child 1 month–11 years:Initially 0. 5 – 1 mg/kg, followed
immediately by (by intravenous infusion)
0. 6 – 3 mg/kg/hour, alternatively (by intravenous
injection or by intraosseous injection) 0. 5 – 1 mg/kg
repeated at intervals of not less than 5 minutes if
infusion is not immediately available following initial
injection, until infusion can be initiated; maximum
3 mg/kg per course
▶Child 12–17 years:Initially 50 – 100 mg, followed by (by
intravenous infusion) 120 mg, dose to be given over
30 minutes, then (by intravenous infusion) 240 mg,
dose to be given over 2 hours, then (by intravenous
infusion) 60 mg/hour, reduce dose further if infusion is
continued beyond 24 hours, if infusion not
immediately available following initial injection, the
initial injection dose may be repeated at intervals of
not less than 5 minutes (to a maximum 300 mg dose in
1 hour) until infusion can be initiated
Neonatal seizures
▶BY INTRAVENOUS INFUSION
▶Neonate:Initially 2 mg/kg, dose to be given over
10 minutes, followed by 6 mg/kg/hour for 6 hours;
reduced to 4 mg/kg/hour for 12 hours, then reduced to
2 mg/kg/hour for a further 12 hours, preterm neonates
may require lower doses.lUNLICENSED USENot licensed for use in children under
1 year.
lCONTRA-INDICATIONSAll grades of atrioventricular block.
severe myocardial depression.sino-atrial disorders
lCAUTIONSAcute porphyrias p. 603 (consider infusion
with glucose for its anti-porphyrinogenic effects).
congestive cardiac failure (consider lower dose).post
cardiac surgery (consider lower dose)
lINTERACTIONS→Appendix 1 : antiarrhythmics
lSIDE-EFFECTSAnxiety.arrhythmias.atrioventricular
block.cardiac arrest.circulatory collapse.confusion.
dizziness.drowsiness.euphoric mood.headache.
hypotension (may lead to cardiac arrest).loss of
consciousness.methaemoglobinaemia.muscle twitching.
myocardial contractility decreased.nausea.neurological
effects.nystagmus.pain.psychosis.respiratory disorders
.seizure.sensation abnormal.temperature sensation
altered.tinnitus.tremor.vision blurred.vomiting
lPREGNANCYCrosses the placenta but not known to be
harmful inanimalstudies—use if benefit outweighs risk.
lBREAST FEEDINGPresent in milk but amount too small to
be harmful.
lHEPATIC IMPAIRMENTCaution—increased risk of side-
effects.76 Arrhythmias BNFC 2018 – 2019
Cardiovascular system2