page158
Contra-indications
left ventricular outlet obstruction
such as hypertrophic cardiomyopathy or aortic ste-
nosis;
phaeochromocytoma,
thrombocytopenia
Pregnancy
no information available—manufacturer
advises avoid
Side-effects
nausea,
vomiting;
tachycardia, brady-
cardia, arrhythmias,
angina,
myocardial infarction;
tremor,
headache;
dyspnoea;
reversible thrombocy-
topenia;
sweating
Dose
. By intravenous infusion into central or large periph-
eral vein,
500 nanograms/kg/minute,
may be
increased to 1 microgram/kg/minute and further
increased up to 6 micrograms/kg/minute in incre-
ments of 0.5–1 microgram/kg/minute at intervals of
not less than 15 minutes
Dopacard
c
(Cephalon) A
Concentrate for intravenous infusion
,
dopexamine
hydrochloride 10 mg/mL (1%). To be diluted before
use.
Net price 5-mL amp = £19.80
Note
Contact
with metal
in infusion apparatus should be mini-
mised
2.7.2
Vasoconstrictor
sympathomimetics
Vasoconstrictor
sympathomimetics
raise blood pres-
sure transiently by acting on alpha-adrenergic receptors
to constrict
peripheral
vessels.
They are sometimes
used as an emergency method of elevating blood pres-
sure where other measures have failed (see also section
2.7.1).
The danger
of
vasoconstrictors is that
although they
raise blood pressure they also reduce perfusion of vital
organs such as the kidney.
Spinal
and epidural
anaesthesia may result
in sympa-
thetic block with resultant
hypotension.
Management
may include intravenous fluids (which are usually given
prophylactically),
oxygen (section 3.6),
elevation of the
legs, and injection of a pressor drug such as ephedrine.
As well
as constricting peripheral
vessels ephedrine
also accelerates the heart rate (by acting on beta recep-
tors).
Use is made of
this dual
action of
ephedrine to
manage associated bradycardia (although intravenous
injection of
atropine sulphate 400 to 600 micrograms
may also be required if bradycardia persists).
EPHEDRINE HYDROCHLORIDE
Indications
see under Dose
Cautions
hyperthyroidism, diabetes mellitus,
ischaemic heart disease,
hypertension,
susceptibility
to angle-closure glaucoma,
elderly;
may cause acute
urine retention in prostatic hypertrophy; interactions:
Appendix 1 (sympathomimetics)
Renal impairment
use with caution
Pregnancy
increased fetal heart rate reported with
parenteral ephedrine
Breast-feeding
irritability and disturbed sleep
reported
Side-effects
nausea,
vomiting,
anorexia;
tachycardia
(sometimes bradycardia), arrhythmias,
anginal pain,
vasoconstriction with hypertension, vasodilation with
hypotension,
dizziness and flushing; dyspnoea;
head-
ache,
anxiety,
restlessness,
confusion,
psychoses,
insomnia, tremor;
difficulty in micturition,
urine
retention;
sweating,
hypersalivation;
changes in
blood-glucose concentration;
very rarely
angle-clo-
sure glaucoma
Dose
. Reversal
of hypotension from spinal or epidural
anaesthesia,
by slow intravenous injection of a solu-
tion containing ephedrine hydrochloride 3 mg/mL, 3–
6 mg (max.
9 mg) repeated every 3–4 minutes
according to response to max.
30 mg
Ephedrine Hydrochloride
(Non-proprietary) A
Injection
,
ephedrine hydrochloride 3 mg/mL,
net
price 10-mL amp = £3.25; 30 mg/mL, net price 1-mL
amp = 41p
METARAMINOL
Indications
acute hypotension (see notes above);
priapism (section 7.4.5) [unlicensed indication]
Cautions
see under Noradrenaline Acid Tartrate;
longer duration of action than noradrenaline (norepi-
nephrine),
see below; cirrhosis
Hypertensive response
Metaraminol has a longer duration
of action than noradrenaline, and an excessive vasopressor
response may cause a prolonged rise in blood pressure
Contra-indications
see under Noradrenaline Acid
Tartrate
Pregnancy
may reduce placental perfusion—manu-
facturer advises use only if potential benefit outweighs
risk
Breast-feeding
manufacturer advises caution—no
information available
Side-effects
see under Noradrenaline Acid Tartrate;
tachycardia; fatal ventricular arrhythmia reported in
Laennec’s cirrhosis
Dose
. By intravenous infusion,
15–100 mg,
adjusted
according to response
. In emergency, by intravenous injection, 0.5–5 mg then
by intravenous infusion,
15–100 mg,
adjusted
according to response
Metaraminol
(Non-proprietary) A
Injection
,
metaraminol 10 mg (as tartrate)/mL
Available from ‘special-order’
manufacturers or specialist
importing companies, see p.
988
NORADRENALINE ACID TARTRATE/
NOREPINEPHRINE BITARTRATE
Indications
see under dose
Cautions
coronary,
mesenteric,
or peripheral vascular
thrombosis; following myocardial infarction,
Prinz-
metal’s variant angina,
hyperthyroidism, diabetes
mellitus;
hypoxia or hypercapnia;
uncorrected hypo-
volaemia;
elderly;
extravasation at injection site may
cause necrosis; interactions: Appendix 1
(sympathomimetics)
Contra-indications
hypertension (monitor blood
pressure and rate of flow frequently)
Pregnancy
avoid—may reduce placental perfusion
Side-effects
hypertension,
headache,
bradycardia,
arrhythmias,
peripheral ischaemia
Dose
. Acute hypotension,
by intravenous infusion,
via cen-
tral venous catheter,
of a solution containing
noradrenaline acid tartrate 80 micrograms/mL
(equivalent to noradrenaline base 40 micrograms/
mL) at an initial rate of 0.16–0.33 mL/minute,
adjusted according to response
138
2.7.2 Vasoconstrictor sympathomimetics
BNF 61
2
Cardiovascular system