Usage
Thiamine mononitrate, also known as vitamin B1, is essential for carbohydrate metabolism and nerve function. It’s prescribed for:
- Thiamine deficiency: This includes conditions like beriberi (both wet and dry), Wernicke-Korsakoff syndrome, and other deficiency-related neurological problems.
- Genetic disorders: Certain genetic conditions like Maple Syrup Urine Disease (MSUD) may benefit from thiamine supplementation.
- Other conditions: While not FDA-approved for these uses, thiamine is sometimes used for conditions like diabetic neuropathy, Alzheimer’s disease, and heart failure, though evidence for benefit is limited.
Pharmacological Classification: Vitamin, nutritional supplement
Mechanism of Action: Thiamine is a precursor to thiamine pyrophosphate (TPP), a crucial coenzyme for several enzymes involved in carbohydrate metabolism, particularly the decarboxylation of pyruvate and alpha-ketoglutarate. TPP is also important for nerve function, likely via its role in myelin sheath maintenance and nerve conduction.
Alternate Names
- Vitamin B1
- Thiamine hydrochloride (another salt form)
- Aneurine hydrochloride
- Aneurine
How It Works
Pharmacodynamics: Thiamine, converted to TPP, facilitates carbohydrate metabolism, energy production, and nerve function.
Pharmacokinetics:
- Absorption: Thiamine is readily absorbed orally in small doses, but absorption can be impaired at high doses or in individuals with gastrointestinal issues or alcohol use disorder. It’s also available in injectable forms (IM and IV) for faster action and bioavailability in severe deficiency.
- Metabolism: Thiamine is converted to its active form, TPP, in the liver.
- Elimination: Primarily renal excretion, both as unchanged thiamine and metabolites.
Mode of Action: TPP acts as a coenzyme for key enzymes in the citric acid cycle and the pentose phosphate pathway, influencing carbohydrate metabolism and energy production. It also plays a role in nerve conduction and myelin synthesis.
Dosage
Standard Dosage
Adults:
- RDA: 1.2 mg/day (males), 1.1 mg/day (females)
- Deficiency: 10-50 mg/day orally, divided into multiple doses. Higher doses (up to 300 mg/day) might be used for severe deficiency, often given parenterally initially.
Children:
- RDA: Varies by age, starting at 0.2 mg/day for infants (0-6 months) and increasing gradually to 1.2 mg/day (males) or 1 mg/day (females) by adolescence.
- Deficiency: 10-50 mg/day orally, divided into multiple doses, adjusted for weight and age.
Special Cases:
- Elderly Patients: May have reduced absorption; monitor and adjust dose as needed.
- Patients with Renal Impairment: Dose adjustments may be necessary in severe renal impairment.
- Patients with Hepatic Dysfunction: Generally well-tolerated; monitor for any signs of toxicity.
- Patients with Comorbid Conditions: Alcoholism, gastrointestinal disorders, or chronic illnesses can influence thiamine needs and absorption; monitor and adjust dose.
Clinical Use Cases
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: Critically ill patients have increased thiamine requirements; monitor and supplement as needed, often parenterally.
- Emergency Situations (e.g., Wernicke encephalopathy): High-dose intravenous thiamine (100 mg or more) followed by IM or IV administration until oral intake is resumed.
Dosage Adjustments
Adjustments are needed based on patient response and clinical condition, particularly renal/hepatic function, alcoholism, gastrointestinal issues, and critically illness.
Side Effects
Common Side Effects
Generally well-tolerated. Rare side effects might include sweating, restlessness, itching, or skin rash.
Rare but Serious Side Effects
Severe allergic reactions (anaphylaxis), though rare, can occur, especially with intravenous administration. Symptoms may include swelling, difficulty breathing, and hives.
Long-Term Effects
No significant long-term effects are known at recommended doses.
Adverse Drug Reactions (ADR)
Rare but serious ADRs include anaphylaxis and pulmonary edema (fluid in the lungs).
Contraindications
Hypersensitivity to thiamine is the main contraindication.
Drug Interactions
Few known drug interactions. High doses might interfere with neuromuscular blocking agents. Some drugs like loop diuretics, phenytoin, and digoxin can lower thiamine levels.
Pregnancy and Breastfeeding
Thiamine is considered safe during pregnancy and breastfeeding at recommended doses (RDA 1.4 mg/day). Higher doses should only be used if clearly needed.
Drug Profile Summary
- Mechanism of Action: Coenzyme for carbohydrate metabolism and nerve function.
- Side Effects: Generally well-tolerated; rare allergic reactions possible.
- Contraindications: Hypersensitivity.
- Drug Interactions: Few known significant interactions.
- Pregnancy & Breastfeeding: Safe at recommended doses.
- Dosage: Varies based on indication and age; RDA for adults is 1.1-1.2 mg/day.
- Monitoring Parameters: Monitor clinical response, particularly in deficiency states or during parenteral administration.
Popular Combinations
Often combined with other B vitamins in B-complex formulations.
Precautions
Screen for hypersensitivity before administration, especially with intravenous route. Monitor renal function in patients with severe kidney disease. Patients with alcohol use disorder or gastrointestinal issues may require higher doses.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Thiamine mononitrate?
A: RDA for adults: 1.2 mg/day (males), 1.1 mg/day (females). Dosage for deficiency states varies, starting from 10-50 mg/day orally.
Q2: How is thiamine administered?
A: Available in oral (tablets, capsules), IM, and IV formulations.
Q3: What are the signs of thiamine deficiency?
A: Beriberi (wet or dry), Wernicke-Korsakoff syndrome, peripheral neuropathy, muscle weakness, fatigue.
Q4: Can pregnant women take thiamine?
A: Yes, considered safe during pregnancy at the RDA of 1.4 mg/day.
Q5: Does thiamine interact with any medications?
A: Few significant interactions. Monitor for possible interactions with neuromuscular blocking agents, loop diuretics, and certain anticonvulsants.
Q6: What is the role of thiamine in the body?
A: Essential for carbohydrate metabolism, energy production, and nerve function.
Q7: Are there any long-term effects of taking high-dose thiamine?
A: No significant long-term side effects are known at recommended doses.
Q8: How quickly does thiamine work?
A: Onset of action depends on the route of administration and the severity of the deficiency. IV administration provides the fastest effect, while oral supplementation may take several days or weeks to replete deficiency.
Q9: What should I do if I miss a dose of thiamine?
A: Take the missed dose as soon as you remember, then carry on with your regular schedule.
