Pharmacopoeias. In Europe, International, and US.
European Pharmacopoeia, 6th ed., 2008 and Supplements 6.1 and 6.2 (Gallamine Triethiodide). A white, or almost white, hygroscopic powder. Very soluble in water; slightly soluble in alcohol; practically insoluble in dichloromethane. Store in airtight containers. Protect from light.
The United States Pharmacopeia 31, 2008, and Supplements 1 and 2 (Gallamine Tnethiodide). A white, hygroscopic, odourless, amorphous powder. Very soluble in water; sparingly soluble in alcohol; very slightly soluble in chloroform. pH of a 2% solution in water is between 5.3 and 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 be raised. It has a small histamine-releasing effect; occasional anaphylactoid reactions have been reported. It should be avoided in patients hypersensitive to iodine and in severe renal impairment. Although competitive muscle relaxants have been given with great care to patients with myasthenia gravis (see Neuromuscular Disorders), UK licensed product information for gallamine triethiodide recommended that it should not be used in such patients.
Cardiopulmonary bypass. Alterations in the pharmacokinetics of competitive neuromuscular blockers in patients undergoing surgery involving cardiopulmonary bypass usually necessitate the use of reduced doses. However, the pharmacokinetics of gallamine in patients undergoing cardiopulmonary bypass appear not to differ significantly from those in control patients.
Renal impairment. Gallamine triethiodide is excreted unchanged in the urine and UK licensed product information considered 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 chronic renal failure given gallamine triethiodide in initial doses of 2 mg/kg intravenously.
For interactions associated with competitive neuromuscular blockers, see Atracurium.
After intravenous use gallamine triethiodide 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 benzylisoquinolinium competitive neuromuscular blocker (see Atracurium). Muscle relaxation occurs within about 1 to 2 minutes after intravenous injection and lasts for about 20 to 30 minutes. It has been used to provide muscle relaxation in general anaesthesia for surgical procedures (see Anaesthesia) and to aid controlled ventilation (see Intensive Care).
Doses of neuromuscular blockers need to be carefully titrated for individual patients according to response, and may vary with the procedure, the other drugs given, and the state of the patient; monitoring of the degree of block is recommended in order to reduce the risk of overdosage. 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 injection have been recommended, with further doses of 20 to 40 mg as required. In children, a dose of 1.5 mg/kg has been recommended, reduced to 600 micrograms/kg for neonates.
In some other countries lower doses have generally been used; an initial dose of 1 mg/kg intravenously, up to a maximum of 80 mg, with additional doses of 0.5 to 1 mg/kg after about 50 to 60 minutes if required.
Gallamine triethiodide has also been given intramuscularly, with or without hyaluronidase.
British Pharmacopoeia 2008; Gallamine Injection;
The United States Pharmacopeia 31, 2008, and Supplements 1 and 2: Gallamine Triethiodide Injection.