Thiamine: clinical use

Prescribing considerations

• Use the parenteral route when rapid restoration is necessary or oral absorption or administration is unreliable.
• Review previous thiamine reactions before injection and ensure facilities for managing anaphylaxis are immediately available.
• Consider increased urinary thiamine loss with long-term diuretic therapy and antagonism by fluoropyrimidines or ifosfamide.

Contraindications and cautions

• Hypersensitivity to thiamine hydrochloride or any formulation excipient.
• The selected tablets contain lactose and are unsuitable for specified rare hereditary disorders of galactose metabolism or absorption.

Monitoring

• Assess clinical response and the continuing cause of deficiency.
• Monitor patients with renal impairment more carefully when using the selected injection.
• Observe during and shortly after parenteral administration for hypersensitivity and injection-site reactions.
• Warn laboratories that thiamine can interfere with some urinary assays and some spectrophotometric theophylline measurements.

Clinical pharmacology

Thiamine is converted intracellularly to thiamine diphosphate, a coenzyme in carbohydrate metabolism. Oral absorption becomes limited at higher quantities; tissue storage is small and excess thiamine or metabolites are excreted in urine.

Formulation and product differences

• The selected tablet is uncoated and contains lactose; its score line facilitates swallowing rather than equal division.
• The selected injection is preservative-free, essentially sodium-free and intended for single use.
• The injection may be administered intramuscularly undiluted or intravenously after dilution with a compatible glucose or sodium chloride solution.

Tablet

Route: Oral

Strengths: 50 mg, 100 mg

Injection

Route: Parenteral

Strengths: 50 mg/mL, 125 mg/mL