Folic Acid is practically insoluble in water but the addition of sodium hydroxide forms soluble sodium folate. Folic Acid injection has a pH of 8 - 11.
Oral solutions and a range of tablet strengths (most brands disperse rapidly) are available in some countries.
The stability of a 1mg per mL folic acid solution for oral use has been briefly reported.1
The following recommendations are made on the basis of this study and from the formulation of the injection.
Formula A
Folic Acid 1mg per mL |
| |
| Folic Acid injection, 15mg per mL |
4 |
mL |
| Parabens |
0.1 |
% |
| *Sodium hydroxide solution 1M |
qs to |
pH 8 |
| Water |
to 60 |
mL |
| |
| *Addition usually unnecessary; only necessary if final
pH < 8 |
| |
|
Expiry: 30 days |
| |
|
Storage: Refrigerate. Protect from light. |
| |
|
|
|
Formula B
Folic Acid 1mg per mL |
| |
| Folic acid tablets 5mg |
10 |
|
| Sodium hydroxide solution 1M |
qs to |
pH 8 |
| Parabens |
0.1 |
% |
| Water |
to 50 |
mL |
| |
|
Expiry: 30 days |
| |
|
Storage: Refrigerate. Protect from light. |
| |
|
|
|
NOTES
- Parabens are suggested on the basis that sodium propyl hydroxybenzoate was used in the
study cited.
- For a preservative free preparation omit the parabens and assign an expiry date of 7 days.
- If sodium hydroxide is not used, folic acid may be in suspension and mixtures should be shaken prior to administration.
REFERENCE
- Smith S.G. A folic acid solution for oral use. Pharm J 1976; February 7: 108
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