Formulation in Pharmacy Practice   2nd Edition

Ethambutol hydrochloride is freely soluble in water.

There is no published information on the stability of an ethambutol hydrochloride oral solution.
The manufacturer of Myambutol® recommends that the daily requirement of tablets is ground to a fine powder and then mixed with about 100mL of apple juice or a small quantity of apple sauce for administration to the patient.  Powders or capsules containing the required dose can also be prepared from the tablets.  Ethambutol hydrochloride powder is available in some countries.  Other fruit juices or syrup are not as satisfactory in disguising the bitter taste.  Although the drug is stable in the apple vehicle for a short time, each dose must be freshly prepared, preferably just before administration.

The following formula was published in Martindale, 29th Edition also on a manufacturer's recommendation:

Ethambutol powder 500mg, citric acid 100mg, orange tincture 0.3mL, syrup 2.5mL, and
double-strength chloroform water to 5mL.

This preparation is reported to be stable for one month but there is no supporting stability information. Until more information is available the preparation of ethambutol solutions for storage over several days is not recommended.

Formulation in Pharmacy Practice
2nd Edition