OMEGAPHARM

What it is

Omegapharm is thiopental sodium 470 mg powder for injection. It is a yellowish hygroscopic powder stabilised with 30 mg anhydrous sodium carbonate per 470 mg of thiopental sodium. Thiopental sodium is an ultra short-acting depressant of the central nervous system, which induces hypnosis and anaesthesia, but not analgesia.

Approved indications

— Sole anaesthetic agent for brief surgical procedures. — Induction of anaesthesia prior to the administration of other anaesthetic agents. — Short-term control of convulsive states. — Supplement to regional anaesthesia or low potency agents such as nitrous oxide.

Dosing overview

Individual response to the drug is so varied that there can be no fixed dosage. The drug should be titrated against patient requirements as governed by age, sex and bodyweight. Omegapharm is administered by the intravenous route only. For induction of anaesthesia, moderately slow induction can usually be accomplished in the average adult by injection of 50 to 75 mg at intervals of 20 to 40 seconds, depending on the reaction of the patient. Once anaesthesia is established, additional injections of 25 to 50 mg can be given whenever the patient needs. For rapid induction in the average adult (70 kg), thiopental sodium 210 to 280 mg (3 to 4 mg/kg) is usually required. For the control of convulsive states following anaesthesia or other causes, 75 to 125 mg should be given as soon as possible after the convulsion begins. In neurosurgical patients, intermittent bolus injections of 1.5 to 3.5 mg/kg bodyweight may be given to reduce intraoperative elevations of intracranial pressure if adequate ventilation is provided.

Key safety warnings

This medicine should be administered only by persons qualified in the use of intravenous anaesthetics. A person competent in anaesthesia management should be in constant attendance and adequate facilities for support of respiration and circulation should be available when Omegapharm is being used. Respiratory depression may result from either an unusual responsiveness to thiopental sodium or an overdosage. Therefore, it should not be administered without the ready availability of resuscitative equipment including that necessary for endotracheal intubation. Extravascular injection may cause chemical irritation of the tissues varying from slight tenderness to venospasm, extensive necrosis and sloughing. This is due primarily to the high alkaline pH (10 to 11) of clinical concentrations of the drug. Intra-arterial injection can occur inadvertently, especially if an aberrant superficial artery is present at the medial aspect of the antecubital fossa. The area selected for intravenous injection of the drug should be palpated for detection of an underlying pulsating vessel. Accidental intra-arterial injection can cause arteriospasm and severe pain along the course of the artery with blanching of the arm and fingers.

Contraindications

Absolute contraindications include complete absence of suitable veins, allergy or hypersensitivity to barbiturates, status asthmaticus or when an adequate airway cannot be maintained during operation, latent or manifest porphyria, constrictive pericarditis, severe respiratory embarrassment, variegate or acute intermittent porphyria, and inflammatory conditions of the mouth, jaw and neck. Relative contraindications include severe cardiovascular disease, hypotension or shock, and conditions in which the hypnotic effect may be prolonged or potentiated such as excessive premedication, Addison's disease, hepatic or renal dysfunction, myxoedema, increased blood urea, severe anaemia, and myasthenia gravis.

Regulatory history

Omegapharm Thiopental Sodium 470 mg powder for injection was first listed on the Australian Register of Therapeutic Goods on 10 November 2015.