Differences Between Thiamine HCl and Thiamine Mononitrate
Thiamine hydrochloride and thiamine mononitrate differ primarily in their chemical stability, solubility, and pH in solution, with thiamine hydrochloride being significantly more stable and having greater solubility, making it preferable for clinical applications requiring solution stability.
Chemical Properties and Stability
- Thiamine hydrochloride (TClHCl) is significantly more stable in solution than thiamine mononitrate (TMN), with studies showing that at 80°C after 5 days, 94% of TClHCl remained intact compared to only 32% of TMN 1
- TClHCl creates more acidic solutions (pH 1.12-3.59) compared to TMN (pH 5.36-6.96), which contributes to its greater stability as thiamine degrades more rapidly in higher pH environments 1, 2
- Both forms follow first-order reaction kinetics for degradation, but TMN degrades significantly faster than TClHCl at all concentrations and temperatures tested 1
Solubility and Formulation Considerations
- TClHCl has greater solubility in water, allowing for higher concentration solutions (up to 500 mg/mL tested) compared to TMN 1
- The degradation products of TClHCl have more noticeable sensory impacts (color changes and aromas) even with less actual vitamin loss, which may be relevant in food fortification applications 1
- Different degradation pathways are observed between the two forms, as evidenced by different HPLC peak patterns 1, 2
Biological Function and Absorption
- Both forms contain thiamine, which is essential for carbohydrate metabolism, energy production, and proper functioning of the nervous system 3, 4
- Thiamine is rapidly absorbed in the jejunum and ileum by an active, carrier-mediated process at lower concentrations and by passive diffusion at higher concentrations 5
- After absorption, both forms are converted to the biologically active form thiamine pyrophosphate (TPP), which serves as a cofactor for enzymes involved in energy metabolism 6, 3
Clinical Applications
- For clinical supplementation, both forms provide thiamine, but the choice may depend on the specific application (oral vs. parenteral, solution stability requirements) 7, 8
- For oral supplementation in mild deficiency, 10 mg/day for one week followed by 3-5 mg/day for at least 6 weeks is recommended, regardless of the salt form 7
- For acute deficiency requiring intravenous administration, doses of 100-300 mg/day are recommended 7, 8
Practical Considerations
- In food fortification, the choice between TMN and TClHCl may impact product shelf life and sensory characteristics 1, 2
- In clinical settings where solution stability is critical (e.g., parenteral nutrition), TClHCl may be preferred due to its superior stability 1
- For patients with suspected thiamine deficiency, the focus should be on prompt supplementation rather than the specific salt form, as both provide the essential vitamin 4
Monitoring and Safety
- Thiamine status can be determined by measuring thiamine diphosphate (ThDP) in whole blood or RBC 7
- No upper limit for toxicity has been established for thiamine, with excess being excreted in urine 7, 8
- High intravenous doses rarely cause anaphylaxis; doses exceeding 400 mg may induce mild side effects such as nausea, anorexia, and mild ataxia 7, 8