ANTIHYPERTENSIVES, CENTRALLY ACTING
Clonidine hydrochloride 01-Jun-2017
lINDICATIONS AND DOSE
Severe hypertension
▶BY MOUTH
▶Child 2–17 years:Initially 0. 5 – 1 microgram/kg 3 times a
day, then increased if necessary up to
25 micrograms/kg daily in divided doses, increase dose
gradually; maximum 1. 2 mg per day
▶BY SLOW INTRAVENOUS INJECTION
▶Child 2–17 years: 2 – 6 micrograms/kg (max. per dose
300 micrograms) for 1 doselUNLICENSED USENot licensed for use in children.
lCONTRA-INDICATIONSSevere bradyarrhythmia secondary
to second- or third-degree AV block or sick sinus
syndrome
lCAUTIONSCerebrovascular disease.constipation.heart
failure.history of depression.mild to moderate
bradyarrhythmia.polyneuropathy.Raynaud’s syndrome
or other occlusive peripheral vascular disease
lINTERACTIONS→Appendix 1 : clonidine
lSIDE-EFFECTS
▶Common or very commonConstipation.depression.
dizziness.dry mouth.fatigue.headache.nausea.
postural hypotension.salivary gland pain.sedation.
sexual dysfunction.sleep disorders.vomiting
▶UncommonDelusions.hallucination.malaise.
paraesthesia.Raynaud’s phenomenon.skin reactions
▶Rare or very rareAlopecia.atrioventricular block.dry eye
.gynaecomastia.intestinal pseudo-obstruction.nasal
dryness
▶Frequency not knownAccommodation disorder.
arrhythmias.confusion
lPREGNANCYMay lower fetal heart rate. Avoid oral use
unless potential benefit outweighs risk. Avoid using
injection.
lBREAST FEEDINGAvoid—present in milk.
lRENAL IMPAIRMENTUse with caution.
lTREATMENT CESSATIONMust be withdrawn gradually to
avoid hypertensive crisis.
lDIRECTIONS FOR ADMINISTRATION
▶With intravenous useForintravenous injection, give over
10 – 15 minutes; compatible with Sodium Chloride 0. 9 %or
Glucose 5 %.
▶With oral useFor administrationby mouth, tablets may be
crushed and dissolved in water.
lPATIENT AND CARER ADVICE
Driving and skilled tasksDrowsiness may affect
performance of skilled tasks (e.g. driving); effects of
alcohol may be enhanced.
lLESS SUITABLE FOR PRESCRIBINGClonidine is less suitable
for prescribing.lMEDICINAL FORMS
There can be variation in the licensing of different medicines
containing the same drug. Forms available from special-order
manufacturers include: oral suspension, oral solution, solution
for injection
Tablet
CAUTIONARY AND ADVISORY LABELS3, 8
▶Clonidine hydrochloride (Non-proprietary)
Clonidine hydrochloride 25 microgramClonidine 25 microgram
tablets| 112 tabletP£ 9. 15 DT = £ 4. 18
▶Catapres(Boehringer Ingelheim Ltd)
Clonidine hydrochloride 100 microgramCatapres 100 microgram
tablets| 100 tabletP£ 8. 04 DT = £ 8. 04Solution for injection
▶Catapres(Boehringer Ingelheim Ltd)
Clonidine hydrochloride 150 microgram per 1 mlCatapres
150 micrograms/ 1 ml solution for injection ampoules|
5 ampouleP£ 2. 09BETA-ADRENOCEPTOR BLOCKERS
Beta-adrenoceptor blocking drugs
Overview
Beta-adrenoceptor blocking drugs (beta-blockers) block the
beta-adrenoceptors in the heart, peripheral vasculature,
bronchi, pancreas, and liver.
Many beta-blockers are available but experience in
children is limited to the use of only a few.
Differences between beta-blockers may affect choice. The
water-soluble beta-blockers, atenolol p. 106 and sotalol
hydrochloride p. 80 , are less likely to enter the brain and may
therefore cause less sleep disturbance and nightmares.
Water-soluble beta-blockers are excreted by the kidneys and
dosage reduction is often necessary in renal impairment.
Some beta-blockers, such as atenolol, have an intrinsically
longer duration of action and need to be given only once
daily. Carvedilol p. 125 and labetalol hydrochloride p. 104 are
beta-blockers which have, in addition, an arteriolar
vasodilating action and thus lower peripheral resistance.
Although carvedilol and labetalol hydrochloride possess
both alpha- and beta-blocking properties, these drugs have
no important advantages over other beta-blockers in the
treatment of hypertension.
Beta-blockers slow the heart and can depress the
myocardium; they are contra-indicated in children with
second- or third-degree heart block.
Beta-blockers can precipitate asthma and should usually
be avoided in children with a history of asthma or
bronchospasm. If there is no alternative, a child with well-
controlled asthma can be treated for a co-existing condition
(e.g. arrhythmia) with a cardioselective beta-blocker, which
should be initiated with caution at a low dose by a specialist
and the child monitored closely for adverse effects. Atenolol
and metoprolol tartrate p. 107 have less effect on the beta 2
(bronchial) receptors and are, therefore, relatively
cardioselective, but they are notcardiospecific; they have a
lesser effect on airways resistance but are not free of this
side-effect.
Beta-blockers are also associated with fatigue, coldness of
the extremities, and sleep disturbances with nightmares
(may be less common with the water-soluble beta-blockers).
Beta-blockers can affect carbohydrate metabolism causing
hypoglycaemia or hyperglycaemia in children with or
without diabetes; they can also interfere with metabolic and
autonomic responses to hypoglycaemia thereby masking
symptoms such as tachycardia. However, beta-blockers are
not contra-indicated in diabetes, although the
cardioselective beta-blockers (e.g. atenolol and metoprolol
tartrate) may be preferred. Beta-blockers should be avoided
altogether in those with frequent episodes of hypoglycaemia.Hypertension
Beta-blockers are effective for reducing blood pressure, but
their mode of action is not understood; they reduce cardiac
output, alter baroceptor reflex sensitivity, and block
peripheral adrenoceptors. Some beta-blockers depress
plasma renin secretion. It is possible that a central effect
may also partly explain their mode of action. Blood pressure
can usually be controlled with relatively few side-effects. In
general the dose of beta-blocker does not have to be high.
Labetalol hydrochloride may be given intravenously for
hypertensive emergenciesin children; however, care is needed
to avoid dangerous hypotension or beta-blockade,
particularly in neonates. Esmolol hydrochloride p. 106 is also102 Blood pressure conditions BNFC 2018 – 2019
Cardiovascular system2