While “Thiamine2” isn’t a recognized medical term, it’s likely referring to thiamine or vitamin B1. This detailed guide provides information on thiamine.
Usage
- Medical Conditions: Thiamine is prescribed for thiamine deficiency (beriberi), Wernicke-Korsakoff syndrome (a neurological disorder often seen in chronic alcoholism), and other conditions related to low thiamine levels like neuritis of pregnancy. It is also used to support patients on parenteral nutrition, those with severe malabsorption, those undergoing hemodialysis, and those with chronic liver disease. Some studies also suggest its use in managing diabetic neuropathy.
- Pharmacological Classification: Vitamin, nutritional supplement.
- Mechanism of Action: Thiamine is a crucial cofactor for enzymes involved in carbohydrate metabolism, particularly in the conversion of pyruvate to acetyl-CoA within the Krebs cycle. This role is essential for energy production, nerve conduction, and muscle function.
Alternate Names
- Alternate Names: Vitamin B1, aneurine (older term).
- Brand Names: Benerva, Thiamine Hydrochloride Injection USP, Tyvera, Athiam, ThiaDose, ThiamEss.
How It Works
- Pharmacodynamics: Thiamine’s primary role is as a coenzyme in vital metabolic processes, supporting energy production, nerve function, and muscle activity.
- Pharmacokinetics:
- Absorption: Thiamine is absorbed in the small intestine, with active transport at nutritional doses and passive diffusion at higher doses.
- Metabolism: Thiamine is converted to its active form, thiamine pyrophosphate (TPP), in the liver.
- Elimination: Excreted primarily through the kidneys, with increased excretion at high doses. Small amounts are excreted in breast milk.
- Mode of Action: Thiamine’s active form, TPP, acts as a cofactor for several enzymes crucial for carbohydrate metabolism including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase. It facilitates the breakdown of glucose and the production of energy.
- Receptor Binding, Enzyme Inhibition or Neurotransmitter Modulation: Thiamine does not directly bind to receptors, inhibit enzymes, or modulate neurotransmitters. Its action is primarily through its coenzyme function within metabolic pathways.
- Elimination Pathways: Primarily renal excretion, with negligible biliary excretion. No significant CYP enzyme metabolism.
Dosage
Standard Dosage
Adults:
- Recommended Dietary Allowance (RDA):
- Males: 1.2 mg/day
- Females: 1.1 mg/day
- Deficiency: 10-50 mg orally daily, divided into multiple doses, or higher doses parenterally for severe deficiency states. Dosing is adjusted according to the severity of the deficiency and individual patient needs.
- Wernicke-Korsakoff Syndrome: 100 mg IV initially, followed by 50-100 mg IM or IV daily until a regular diet can be resumed.
Children:
- RDA: Varies with age, ranging from 0.2 mg/day for infants 0-6 months to 1.2 mg/day for adolescent males.
- Deficiency: 10-50 mg/day orally, divided into doses, or adjusted based on weight and severity. Pediatric safety considerations include careful dosing and monitoring for adverse reactions. Parenteral administration should be done cautiously in children, with slow IV infusions preferred.
Special Cases:
- Elderly Patients: May have lower blood levels of thiamine, requiring supplementation.
- Patients with Renal Impairment: Dose adjustment is often necessary due to reduced clearance.
- Patients with Hepatic Dysfunction: Careful monitoring is needed due to the liver’s role in thiamine metabolism. Dose adjustments may be considered based on liver function.
- Patients with Comorbid Conditions: Adjustments may be needed for patients with conditions impacting thiamine absorption or metabolism.
Clinical Use Cases
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: Thiamine supplementation is often given to critically ill patients to prevent or treat deficiency, often through intravenous administration.
- Emergency Situations: High-dose IV thiamine (e.g., 100 mg) is used in emergencies like Wernicke’s encephalopathy, severe beriberi with cardiac involvement, or in individuals with altered mental status of unknown etiology.
Dosage Adjustments:
Dose modifications are needed for patients with renal/hepatic dysfunction and based on the severity of thiamine deficiency.
Side Effects
Common Side Effects
- Flushing, sweating, warmth, mild rash, itching, nausea, restlessness, feeling of throat tightness. Injection site reactions (tenderness, hard lump).
Rare but Serious Side Effects
- Severe allergic reactions (anaphylaxis, angioedema, pulmonary edema), difficulty swallowing, cyanosis, wheezing/difficulty breathing, GI bleeding.
Long-Term Effects:
Limited information available. High doses may theoretically interfere with other nutrient absorption.
Adverse Drug Reactions (ADR):
As listed in the “Rare but serious side effects” section.
Contraindications
- Hypersensitivity to thiamine.
- Caution in patients with renal impairment due to the aluminum content in some parenteral preparations.
Drug Interactions
- Fluorouracil: Thiamine may reduce the effectiveness of fluorouracil.
- Some antibiotics (erythromycin, clarithromycin) can potentially decrease thiamine absorption when taken orally.
- Caffeine and excessive coffee/tea consumption may slightly reduce thiamine absorption.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: A (injectable), C (oral doses exceeding RDA).
- Fetal Risks/Teratogenicity: No evidence of significant fetal harm at recommended doses.
- Breastfeeding: Small amounts are excreted in breast milk, but generally considered safe at recommended doses.
Drug Profile Summary
- Mechanism of Action: Coenzyme for carbohydrate metabolism, essential for energy production.
- Side Effects: Commonly flushing, sweating, nausea, rash. Rarely, anaphylaxis.
- Contraindications: Hypersensitivity to thiamine. Caution in renal impairment (parenteral).
- Drug Interactions: Fluorouracil, some antibiotics (oral), caffeine.
- Pregnancy & Breastfeeding: Generally safe at recommended doses.
- Dosage: Varies depending on indication and age. See detailed dosage guidelines above.
- Monitoring Parameters: Thiamine levels (in research settings), resolution of deficiency symptoms, monitoring renal function with high-dose parenteral use.
Popular Combinations
Thiamine is often included in multivitamin preparations and B-complex formulations. It can be co-administered with other vitamins or medications as needed for specific conditions.
Precautions
- Assess for underlying causes of thiamine deficiency.
- Monitor renal function in patients receiving high-dose parenteral thiamine.
- Administer IV thiamine slowly to minimize the risk of hypotension or anaphylaxis.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Thiamine?
A: The RDA for adults is 1.2 mg/day for males and 1.1 mg/day for females. Therapeutic doses for deficiency states are significantly higher and depend on the severity and clinical presentation.
Q2: How should thiamine be administered in Wernicke’s encephalopathy?
A: 100 mg IV initially, followed by 50-100 mg IM or IV daily until a regular diet can be resumed.
Q3: What are the common side effects of thiamine?
A: Flushing, sweating, warmth, mild rash, itching, nausea, restlessness, and injection site reactions are common. Severe allergic reactions are rare but possible.
Q4: Are there any contraindications to thiamine use?
A: Hypersensitivity to thiamine. Caution with parenteral administration in patients with renal impairment due to the aluminum content of some formulations.
Q5: Can thiamine be given during pregnancy and breastfeeding?
A: Generally considered safe at recommended doses. Higher doses should be used with caution and under medical supervision.
Q6: How does thiamine interact with other medications?
A: It may decrease the efficacy of fluorouracil. Certain antibiotics can interfere with oral absorption. Caffeine can slightly reduce absorption.
A: Acts as a coenzyme for crucial enzymes involved in glucose breakdown and energy production.
Q8: How is thiamine deficiency diagnosed?
A: Blood tests for thiamine levels can be done, although measuring erythrocyte transketolase activity is considered more reliable. Clinical presentation and dietary history also contribute to the diagnosis.
Q9: What foods are good sources of thiamine?
A: Pork, beef, legumes, nuts, whole grains, and enriched cereals are good sources of thiamine.
