BNF for Children 2011-2012

BNFC 2011–2012 2.4 Beta-adrenoceptor blocking drugs 87Neonatal seizures (section 4.8.1). By intravenous infusionNeonate initially 2 mg/kg over 10 minutes, followedby 6 mg/kg/hour for 6 hours; reduce doseover the following 24 hours (4 mg/kg/hour for 12hours, then 2 mg/kg/hour for 12 hours)Note Preterm neonates may require lower dosesEye section 11.7Local anaesthesia section 15.2Administration for intravenous infusion, dilute withGlucose 5% or Sodium Chloride 0.9%Lidocaine (Non-proprietary) AInjection 1%, lidocaine hydrochloride 10 mg/mL, netprice 2-mL amp = 21p; 5-mL amp = 26p; 10-mL amp= 39p; 20-mL amp = 78pInjection 2%, lidocaine hydrochloride 20 mg/mL, netprice 2-mL amp = 32p; 5-mL amp = 31p; 10-mL amp= 60p; 20-mL amp = 80pInfusion, lidocaine hydrochloride 0.1% (1 mg/mL)and 0.2% (2 mg/mL) in glucose intravenous infusion5%. 500-mL containersMinijet c Lidocaine (UCB Pharma) AInjection, lidocaine hydrochloride 1% (10 mg/mL),net price 10-mL disposable syringe = £8.48; 2%(20 mg/mL), 5-mL disposable syringe = £8.182.4 Beta-adrenoceptorblocking drugsBeta-adrenoceptor blocking drugs (beta-blockers) blockthe beta-adrenoceptors in the heart, peripheral vasculature,bronchi, pancreas, and liver.Many beta-blockers are available but experience inchildren is limited to the use of only a few.Differences between beta-blockers may affect choice.The water-soluble beta-blockers, atenolol and sotalol,are less likely to enter the brain and may therefore causeless sleep disturbance and nightmares. Water-solublebeta-blockers are excreted by the kidneys and dosagereduction is often necessary in renal impairment.Some beta-blockers, such as atenolol, have an intrinsicallylonger duration of action and need to be given onlyonce daily. Carvedilol and labetalol are beta-blockerswhich have, in addition, an arteriolar vasodilating actionand thus lower peripheral resistance. Although carvediloland labetalol possess both alpha- and beta-blockingproperties, these drugs have no important advantagesover other beta-blockers in the treatment of hypertension.Beta-blockers slow the heart and can depress the myocardium;they are contra-indicated in children withsecond- or third-degree heart block. Sotalol may prolongthe QT interval, and it occasionally causes lifethreateningventricular arrhythmias (important: particularcare is required to avoid hypokalaemia in childrentaking sotalol).Beta-blockers can precipitate asthma and should usuallybe avoided in children with a history of asthma orbronchospasm. If there is no alternative, a child withwell-controlled asthma can be treated for a co-existingcondition (e.g. arrhythmia) with a cardioselective betablocker,which should be initiated with caution at a lowdose by a specialist and the child monitored closely foradverse effects. Atenolol and metoprolol have less effecton the beta 2 (bronchial) receptors and are, therefore,relatively cardioselective, but they are not cardiospecific;they have a lesser effect on airways resistance butare not free of this side-effect.Beta-blockers are also associated with fatigue, coldnessof the extremities, and sleep disturbances with nightmares(may be less common with the water-solublebeta-blockers, see above).Beta-blockers can affect carbohydrate metabolism causinghypoglycaemia or hyperglycaemia in children withor without diabetes; they can also interfere with metabolicand autonomic responses to hypoglycaemia therebymasking symptoms such as tachycardia. However, betablockersare not contra-indicated in diabetes, althoughthe cardioselective beta-blockers (e.g. atenolol andmetoprolol) may be preferred. Beta-blockers should beavoided altogether in those with frequent episodes ofhypoglycaemia.Pregnancy Beta-blockers may cause intra-uterinegrowth restriction, neonatal hypoglycaemia, and bradycardia;the risk is greater in severe hypertension. Theuse of labetalol in maternal hypertension is not knownto be harmful, except possibly in the first trimester.Information on the safety of carvedilol duringpregnancy is lacking. If beta-blockers are used close todelivery, infants should be monitored for signs of betablockade(and alpha-blockade with labetalol or carvedilol).For the treatment of hypertension in pregnancy,see section 2.5.Breast-feeding Infants should be monitored as thereis a risk of possible toxicity due to beta-blockade (andalpha-blockade with labetalol or carvedilol), but theamount of most beta-blockers present in milk is toosmall to affect infants. Atenolol and sotalol are presentin milk in greater amounts than other beta-blockers. Themanufacturer of esmolol advises avoidance if breastfeeding.Hypertension Beta-blockers are effective for reducingblood pressure (section 2.5), but their mode of action isnot understood; they reduce cardiac output, alter baroceptorreflex sensitivity, and block peripheral adrenoceptors.Some beta-blockers depress plasma renin secretion.It is possible that a central effect may also partlyexplain their mode of action. Blood pressure can usuallybe controlled with relatively few side-effects. In generalthe dose of beta-blocker does not have to be high.Labetalol may be given intravenously for hypertensiveemergencies in children (section 2.5); however, care isneeded to avoid dangerous hypotension or beta-blockade,particularly in neonates. Esmolol is also usedintravenously for the treatment of hypertension particularlyin the peri-operative period.Beta-blockers can be used to control the pulse rate inchildren with phaeochromocytoma (section 2.5.4).However, they should never be used alone as betablockadewithout concurrent alpha-blockade may leadto a hypertensive crisis; phenoxybenzamine shouldalways be used together with the beta-blocker.2 Cardiovascular system