ADMINISTRATION ROUTES:
IV, IM, PO
ALTERNATIVE NAMES:
Apo thiamine, Vitamin B1
ICU INDICATIONS:
- Treatment / prophylaxis of vitamin B1 deficiency
PRESENTATION AND ADMINISTRATION:
IV/IM:
100 mg in 1 mL solution
For IM administration, solution may be injected undiluted into a large muscle mass
For IV injection, administer by direct IV slow injection over 10 minutes into a vein or side arm of a running infusion. Can be diluted in compatible IV fluid if required.
Compatible with the following IV fluids: 5% dextrose 0.9% sodium chloride
Store at room temperature
Protect from light
Note: Section 29 drug (requires specific notification to Director-General of Health as unapproved route of administration)
PO:
Tablets:
Apo-thiamine 50 mg tablets (white)
DOSAGE:
PO:
50 mg OD
This dose is for thiamine replacement. Usual daily requirement is only 0.8 - 1.5 mg/day
IV:
100 mg IV OD
Wernicke's encephalopathy:
200 mg IV TDS for 3 days then 100 mg IV/PO OD
DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:
Dose as in normal renal function
DOSAGE IN PAEDIATRICS:
1 - 2 mg/kg IV/PO OD
CLINICAL PHARMACOLOGY:
Thiamine (vitamin B1) is a water-soluble vitamin essential for carbohydrate metabolism. It is a cofactor for enzymes including pyruvate dehydrogenase and transketolase. This in turn leads to a failure of aerobic metabolism causing lactate production. It occurs naturally in specific diets (brown rice, pork, nuts, peas) and in enriched grain products (bread & cereals). Prolonged or untreated deficiency can lead to Wernicke encephalopathy, Korsakoff syndrome, or beriberi. The latter may be 'dry' (presenting with peripheral neuropathy) or 'wet' (peripheral oedema and high-output cardiac failure).
Thiamine has a limited storage duration with rapid excretion meaning consistent and regular dietary intake is required to maintain serum levels.
Thiamine deficiency may be due to
- Poor intake: chronic alcohol use, elderly, social isolation, eating disorders
- Impaired absorption: chronic alcohol use, Crohn's or coeliac disease, gastrectomy or bariatric surgery
- Increased requirements: sepsis, pregnancy, hyperthryoidism
- Excess carbohydrate load: refeeding, high-glucose IV fluids without thiamine supplementation
- Increased losses: long-term dialysis, diuretics
CONTRAINDICATIONS:
- Hypersensitivity to thiamine preparations
WARNINGS:
Administration of Glucose:
In patients with potential thiamine deficiency, thiamine should be administered prior to glucose even in the presence of hypoglycaemia. Thiamine is a necessary cofactor for glucose metabolism. Administration of IV glucose alone has caused permanent brain stem damage when administered to thiamine deficient patients (particularly alcoholics)
Sensitivity reactions and intravenous use:
Serious sensitivity reactions can occur. Deaths have resulted from intravenous use (use IV route with caution)
PRECAUTIONS:
General:
See WARNINGS
Laboratory Tests:
No tests additional to routine ICU tests are required
Drug/Laboratory Test Interactions:
None known
IMPORTANT DRUG INTERACTIONS IN ICU:
None of note
ADVERSE REACTIONS:
General:
Sensitivity or intolerance to thiamine may develop, especially after repeated intravenous administration. Some tenderness and induration may follow intramuscular use.
Dermatological:
Pruritis, urticaria
Cardiovascular:
Pulmonary oedema
Respiratory:
Angioneurotic oedema
Gastrointestinal:
Nausea, haemorrhage into the gastrointestinal tract