Monograph: |
Gallamine Triethiodide
A white, or almost white, hygroscopic odourless amorphous
powder. Very soluble in water: slightly to sparingly soluble in
alcohol: very slightly soluble in chloroform: practically insol-
uble in dichloromethane and in ether. A 2% solution in water
has a pH of 5.3 to 7.0. Store in airtight containers. Protect
from light.
Adverse Effects, Treatment, and Precautions
As for competitive neuromuscular blockers in general (see
Atracurium . Tachycardia often develops due to the
vagolytic action of gallamine triethiodide and blood pressure
may occasionally be raised. It has a small histamine-releasing
effect: occasional anaphylactoid reactions have been report-
ed. It should be avoided in patients hypersensitive to iodine.
Although competitive muscle relaxants have been given with
great care to patients with myasthenia gravis (see Neuromus-
cular Disorders, the manufacturer of gallamine tri-
ethiodide recommends that it should not be used in such
patients.
Cardiopulmonary bypass. Alterations in the pharmacoki-
netics of competitive neuromuscular blockers in patients un-
dergoing surgery involving cardiopulmonary bypass usually
necessitate the use of reduced doses . However.
the pharmacokinetics of gallamine in patients undergoing car-
diopulmonary bypass appear not to differ significantly from
those in control patients.
Renal impairment. Gallamine triethiodide is excreted un-
changed in the urine and some consider that it should be
avoided in severe renal impairment since prolonged-paralysis
may occur. Significantly prolonged elimination half-life and
reduced clearance have been reported' in patients with chron-
ic renal failure given gallamine triethiodide in initial doses of
2 mg per kg body-weight intravenously.
Interactions
For interactions associated with competitive neuromuscular
blockers. see Atracurium.
Pharmacokinetics
Following intravenous administration, gallamine
is distributed throughout body tissues. It is not metabolised,
and is excreted in the urine as unchanged drug.
Uses and Administration
Gallamine triethiodide is a benzylisoquinolinitim competitive
neuromuscular blocker (sec Atracurium). Muscle re-
laxation occurs within about I to 2 minutes following intrave-
nous injection and lasts for about 20 to 30 minutes. It is used
to provide muscle relaxation in general anaesthesia for surgi-
cal procedures and to aid mechanical ventilation .
An initial test dose of 20 mg may be given intravenously to
the patient before anaesthesia to determine undue sensitivity.
In the UK. initial doses of 80 to 120 mg by intravenous injec-
tion have been recommended , with further doses of 20 to
40 mg as required. In children, a dose of 1.5 mg per kg body-
weight has been recommended, reduced to 600 ng per kg for
neonates.
In the USA and some other countries lower doses have gener-
ally been employed: an initial dose of 1 mg per kg intrave-
nously, up to a maximum of 100 mg, with additional doses of
0.5 to 1 mg per kg after about 30 to 40 minutes or longer if
required.
Where intravenous administration is not feasible, gallamine
triethiodide may be given intramuscularly, with or without
hyaluronidase.
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