The solubility of isoniazid in water is approximately 1 in 8. The pH of a 1% aqueous solution is 5.5 - 6.5. The pH of isoniazid injection is adjusted to 6 - 7. Isoniazid may crystallise from solution at low temperatures. If this occurs products should be gently warmed to room temperature to redissolve. No formal stability studies of isoniazid oral liquids have been located.
Formula A is based on information published in the British Pharmaceutical Codex (BPC 1973) and Martindale (29th Edition). Formula B is a suggested alternative.
Formula A
Isoniazid Solution 50mg per 5mL |
| |
| Isoniazid powder BP |
1000 |
mg |
| Citric acid monohydrate |
250 |
mg |
| #Sodium citrate |
1200 |
mg |
| Glycerol |
20 |
mL |
| Parabens |
0.1 |
% |
| Water |
to 100 |
mL |
| |
The original formula contained chloroform water as a preservative.
Parabens is suggested as
an alternative. Concentrated anise water has also been omitted.
#The inclusion of sodium citrate is preferred to provide a pH buffer system. However,
citric acid alone is probably sufficient for an expiry date not exceeding 30 days. |
| |
|
Expiry: 30 days |
| |
Storage: Room temperature (less than 25°C) or refrigerate.
If stored in a refrigerator check for crystallisation and warm to room temperature to redissolve if
necessary.
Protect from light and store in amber containers. |
| |
|
Shake well before use |
| |
NOTES
- Do not use syrups (glucose, fructose, sucrose etc.) in the formulation due to incompatibility with isoniazid.
- If isoniazid powder is not available crushed tablets could be used but insoluble excipients will form a suspension. A suspending agent such as 1% methylcellulose is recommended.
- A modified version of Formula A using crushed tablets is as follows:
Isoniazid tablets qs; Citric acid monohydrate 250mg; Glycerol 20mL; Parabens 0.1%;
Methylcellulose 1%, 50mL; Water to 100mL.
It is essential to shake this preparation before use as drug may be bound to excipients or may have
precipitated from solution.
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| |
|
|
|
Formula B1
Isoniazid Suspension 100mg per 5mL |
| |
| Isoniazid tablets 100mg |
30 |
|
| HPMC
1% mucilage |
75 |
mL |
| Water |
20 |
mL |
| Sorbitol solution 70 % |
to 150 |
mL |
| |
|
Expiry: 30 days |
| |
|
Storage: Refrigerate. Protect from light. Use amber
containers. |
| |
|
Shake well before use |
| |
NOTE
- Nahata and Hipple2 have described the following formulation also
using sorbitol:
Isoniazid tablets (10 x 100mg) crushed and mixed with 10mL of water and made up to 100ml with sorbitol
70%. A stability period of 21 days under refrigeration was stated although no formal
testing was carried out.
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REFERENCES
- Personal Communication: Ron Chambers, PMH, Perth, Western Australia.
- Nahata MC, Hipple TF. Pediatric Drug Formulations. Cincinnati, Ohio: Harvey Whitney Books
Company; 1992.
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