BNF for Children 2011-2012

BNFC 2011–2012 2.5.1 Vasodilator antihypertensive drugs 93organ damage. Treatment should be initiated with intravenousdrugs; once blood pressure is controlled, oraltherapy can be started. It may be necessary to infusefluids particularly during the first 12 hours to expandplasma volume should the blood pressure drop toorapidly.Controlled reduction of blood pressure is achieved byintravenous administration of labetalol (section 2.4) orsodium nitroprusside (section 2.5.1.1). Esmolol (section2.4) is useful for short-term use and has a shortduration of action. Nicardipine (section 2.6.2) can beadministered as a continuous intravenous infusion but itis not licensed for this use. In less severe cases, nifedipinecapsules (section 2.6.2) can be used.In resistant cases, diazoxide (section 2.5.1.1) is givenintravenously, but it can cause sudden hypotension.Other antihypertensive drugs which can be given intravenouslyinclude hydralazine (section 2.5.1.1) and clonidine(section 2.5.2).Hypertension in acute nephritis occurs as a result ofsodium and water retention; it should be treated withsodium and fluid restriction, and with furosemide (section2.2.2); antihypertensive drugs may be added ifnecessary.For advice on short-term management of hypertensiveepisodes in phaeochromocytoma, see under Phaeochromocytoma,section 2.5.4.2.5.1 Vasodilatorantihypertensive drugsand pulmonaryhypertension2.5.1.1 Vasodilator antihypertensivesVasodilators have a potent hypotensive effect, especiallywhen used in combination with a beta-blockerand a thiazide. Important: for a warning on the hazardsof a very rapid fall in blood pressure, see HypertensiveEmergencies, p. 92.Sodium nitroprusside is given by intravenous infusionto control severe hypertensive crisis when parenteraltreatment is necessary. At low doses it reduces systemicvascular resistance and increases cardiac output; at highdoses it can produce profound systemic hypotension—continuous blood pressure monitoring is thereforeessential. Sodium nitroprusside may also be used tocontrol paradoxical hypertension after surgery forcoarctation of the aorta.Diazoxide has also been used by intravenous injectionin hypertensive emergencies; however it is not first-linetherapy.Hydralazine is given by mouth as an adjunct to otherantihypertensives for the treatment of resistant hypertensionbut is rarely used; when used alone it causestachycardia and fluid retention. The incidence of sideeffectsis lower if the dose is kept low, but systemic lupuserythematosus should be suspected if there is unexplainedweight loss, arthritis, or any other unexplainedill health.Minoxidil should be reserved for the treatment ofsevere hypertension resistant to other drugs. Vasodilatationis accompanied by increased cardiac output andtachycardia and children develop fluid retention. Forthis reason the addition of a beta-blocker and a diuretic(usually furosemide, in high dosage) are mandatory.Hypertrichosis is troublesome and renders this drugunsuitable for females.Prazosin and doxazosin (section 2.5.4) have alphablockingand vasodilator properties.DIAZOXIDECautions during prolonged use monitor white cell andplatelet count, and regularly assess growth, bone, andpsychological development; interactions: Appendix 1(diazoxide)Renal impairment dose reduction may be requiredPregnancy prolonged use may produce alopecia,hypertrichosis, and impaired glucose tolerance inneonate; inhibits uterine activity during labourBreast-feeding manufacturer advises avoid—noinformation availableSide-effects tachycardia, hypotension, hyperglycaemia,sodium and water retention; rarely cardiomegaly,hyperosmolar non-ketotic coma, leucopenia,thrombocytopenia, and hirsuitismLicensed use tablets not licensed for resistanthypertensionIndication and doseHypertensive emergencies initiated on specialistadvice. By intravenous injectionChild 1 month–18 years 1–3 mg/kg (max.150 mg) as a single dose, repeat dose after 5–15minutes until blood pressure controlled; max. 4doses in 24 hoursResistant hypertension. By mouthNeonate initially 1.7 mg/kg 3 times daily, adjustedaccording to response; usual max. 15 mg/kg dailyChild 1 month–18 years initially 1.7 mg/kg 3times daily, adjusted according to response; usualmax. 15 mg/kg dailyIntractable hypoglycaemia section 6.1.4Administration intravenous injection over 30 seconds.Do not diluteEudemine c (Goldshield) AUInjection, diazoxide 15 mg/mL, net price 20-mL amp= £30.00Tablets, see section 6.1.4Extemporaneous formulations available seeExtemporaneous Preparations, p. 6HYDRALAZINE HYDROCHLORIDECautions cerebrovascular disease; occasionally bloodpressure reduction too rapid even with low parenteraldoses; manufacturer advises test for antinuclear factorand for proteinuria every 6 months and check acetylatorstatus before increasing dose, but evidence ofclinical value unsatisfactory; interactions: Appendix1 (hydralazine)2 Cardiovascular system