BNF for Children 2011-2012

100 2.5.5 Drugs affecting the renin-angiotensin system BNFC 2011–20122 Cardiovascular systemCongestive heart failure (but rarely used, seesection 2.2). By mouthChild 1 month–12 years 5 micrograms/kg twicedaily (initial dose at bedtime), increased graduallyto max. 100 micrograms/kg daily in divided dosesChild 12–18 years 500 micrograms 2–4 timesdaily (initial dose at bedtime), increasing to 4 mgdaily in divided doses; maintenance 4–20 mg dailyin divided dosesAdministration for administration by mouth, tabletsmay be dispersed in waterPrazosin (Non-proprietary) ATablets, prazosin (as hydrochloride) 500 micrograms,net price 56-tab pack = £2.51; 1 mg, 56-tab pack =£3.23; 2 mg, 56-tab pack = £4.39; 5 mg, 56-tab pack =£8.75. Counselling, initial dose, drivingHypovase c (Pfizer) ATablets, prazosin (as hydrochloride) 500 micrograms,net price 60-tab pack = £2.69; 1 mg, scored, 60-tabpack = £3.46. Counselling, initial dose, drivingPhaeochromocytomaLong-term management of phaeochromocytomainvolves surgery. However, surgery should not takeplace until there is adequate blockade of both alphaandbeta-adrenoceptors. Alpha-blockers are used in theshort-term management of hypertensive episodes inphaeochromocytoma. Once alpha blockade is established,tachycardia can be controlled by the cautiousaddition of a beta-blocker (section 2.4); a cardioselectivebeta-blocker is preferred. There is no nationwide consensuson the optimal drug regimen or doses used forthe management of phaeochromocytoma.Phenoxybenzamine, a powerful alpha-blocker, is effectivein the management of phaeochromocytoma but ithas many side-effects.PHENOXYBENZAMINEHYDROCHLORIDECautions congestive heart failure; severe ischaemicheart disease (see also Contra-indications); cerebrovasculardisease (avoid if history of cerebrovascularaccident); monitor blood pressure regularly duringinfusion; carcinogenic in animals; avoid in acuteporphyria (section 9.8.2); avoid extravasation (irritantto tissues); avoid contact with skin (risk of contactsensitisation)Contra-indications history of cerebrovascular accident;avoid infusion in hypovolaemiaRenal impairment use with cautionPregnancy hypotension in newborn may occurBreast-feeding may be present in milkSide-effects postural hypotension with dizziness andmarked compensatory tachycardia, lassitude, nasalcongestion, miosis, inhibition of ejaculation; rarelygastro-intestinal disturbances; decreased sweatingand dry mouth after intravenous infusion; idiosyncraticprofound hypotension within few minutes ofstarting infusion; convulsions following rapid intravenousinfusion also reportedLicensed use not licensed for use in childrenIndication and doseHypertension in phaeochromocytoma. By mouthChild 1 month–18 years 0.5–1 mg/kg twice dailyadjusted according to response. By intravenous infusionChild 1 month–18 years 0.5–1 mg/kg dailyadjusted according to response; occasionally up to2 mg/kg daily may be required; do not repeat dosewithin 24 hoursAdministration for administration by mouth, capsulesmay be opened.For intravenous infusion, dilute with Sodium Chloride0.9% and give over at least 2 hours; max. 4 hoursbetween dilution and completion of infusionPhenoxybenzamine (Goldshield) AInjection concentrate, phenoxybenzamine hydrochloride50 mg/mL. To be diluted before use. Netprice 2-mL amp = £57.14 (hosp. only)Dibenyline c (Goldshield) ACapsules, red/white, phenoxybenzamine hydrochloride10 mg. Net price 30-cap pack = £10.842.5.5 Drugs affecting the reninangiotensinsystem2.5.5.1 Angiotensin-converting enzymeinhibitors2.5.5.2 Angiotensin-II receptor antagonists2.5.5.1 Angiotensin-converting enzymeinhibitorsAngiotensin-converting enzyme inhibitors (ACE inhibitors)inhibit the conversion of angiotensin I to angiotensinII. The main indications of ACE inhibitors inchildren are shown below. In infants and young children,captopril is often considered first.Initiation under specialist supervision Treatmentwith ACE inhibitors should be initiated under specialistsupervision and with careful clinical monitoring in children.Heart failure ACE inhibitors have a valuable role in allgrades of heart failure, usually combined with a loopdiuretic (section 2.2). Potassium supplements and potassium-sparingdiuretics should be discontinued beforeintroducing an ACE inhibitor because of the risk ofhyperkalaemia. In adults, a low dose of spironolactonemay be beneficial in severe heart failure and can be usedwith an ACE inhibitor provided serum potassium ismonitored carefully. Profound first-dose hypotensioncan occur when ACE inhibitors are introduced to childrenwith heart failure who are already taking a highdose of a loop diuretic (see Cautions below). Temporarywithdrawal of the loop diuretic reduces the risk, but cancause severe rebound pulmonary oedema.