Ethambutol Hydrochloride Compounded Oral Suspension USP (100 mg/mL)

US Pharm. 2017;42(8):48-49.

Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Comminute the ethambutol tablets to a fine powder. Add a small quantity of Ora-Plus and mix to form a smooth paste. Geometrically, add the remainder of the Ora-Plus and mix well. In portions, add the Ora-Sweet SF and mix well. Package and label.

Use: Ethambutol hydrochloride oral suspension is indicated for the treatment of pulmonary tuberculosis. It should not be used as the sole antituberculous drug, but should be administered in conjunction with at least one other antituberculous drug.

Packaging: Package in tight, light-resistant containers.

Labeling: Keep out of reach of children. Shake well. Discard after ____ [time period].

Stability: A beyond-use date of not more than 90 days when stored at either refrigerator or controlled room temperature may be used for this preparation.¹

Quality Control: Quality-control assessment can include weight/volume, pH (between 3.5 and 5.6), specific gravity, active drug assay, color, rheologic properties/pourability, physical observation, and physical stability (discoloration, foreign materials, gas formation, mold growth).²

Discussion: The formulation presented here is one of the almost 200 official formulas contained in the USP, with beyond-use dates, for both human and animal patients. The USP compounded-preparation monographs contain formulations and quality standards for specific preparations to assist in compounding preparations for which no suitable commercial product is available.

Each monograph includes:

• Formula (ingredients and quantities)
• Instructions concerning how to correctly compound the preparation
• Beyond-use dates based on stability studies using stability-indicating analytical methods
• Packaging and storage information
• Acceptable pH ranges
• Stability-indicating assays

Ethambutol is a medication that is primarily used to treat tuberculosis. It is an oral chemotherapeutic agent that is specifically effective against actively growing microorganisms of the genus Mycobacterium, including Mycobacterium tuberculosis. It is usually given in combination with other tuberculosis medications, such as isoniazid, rifampicin, and pyrazinamide.

Ethambutol hydrochloride (Myambutol, C₁₀H₂₄N₂O₂.2HCl, MW 277.23) occurs as a white, crystalline powder that is freely soluble in water (1 g in 1 mL) and soluble in alcohol (1 g in 4 mL). It is hygroscopic when exposed to high relative humidity. Ethambutol hydrochloride melts at about 198°C to 202°C. Ethambutol hydrochloride should be preserved in a well-closed container, and it is stable in both light and heat.³ Myambutol (ethambutol hydrochloride) 100-mg and 400-mg tablets also contain the following inactive ingredients: either gelatin, hydroxypropyl methylcellulose, magnesium stearate, sodium lauryl sulfate, sorbitol, stearic acid, sucrose, titanium dioxide, and other ingredients or colloidal silicon dioxide, cornstarch, magnesium stearate, povidone, and talc. The film coating contains ethyl cellulose, macrogol, hypromellose, propylene glycol, talc, and titanium dioxide.^4,5

Ora-Plus is an oral suspending vehicle that accepts dilution of up to 50% or more with water, flavoring agents, or syrups while still retaining its suspending properties. It has a pH of approximately 4.2 and an osmolality of about 230 mOsm/kg. Ora-Plus is a thixotropic vehicle with a viscosity of approximately 1,000 cps at 25°C. It contains purified water, microcrystalline cellulose, sodium carboxymethyl cellulose, xanthan gum, carrageenan, sodium phosphate, and citric acid as buffering agents; simethicone as an antifoaming agent; and potassium sorbate and methylparaben as preservatives.⁶

Ora-Sweet SF sugar-free syrup vehicle is a flavoring vehicle for oral extemporaneous preparations. It is a sugar-free, alcohol-free syrup flavored with a citrus-berry flavor blend. Ora-Sweet SF is buffered to a pH of approximately 4.2, and it may be used alone or in combination with other vehicles. Ora-Sweet SF will tolerate a dilution to 50% with dissolved actives in water or suspending agents while still retaining an acceptable taste. It has an osmolality of 2,150 mOsm/kg. Ora-Sweet SF contains water, sodium saccharin, xanthan gum, glycerin, sorbitol, citric acid, and sodium citrate as buffers; methylparaben, propylparaben, and potassium sorbate as preservatives; and flavoring agents.⁷

REFERENCES

1. U.S. Pharmacopeia/National Formulary [current revision]. Rockville, MD: U.S. Pharmacopeial Convention, Inc; June 2017.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of oral and topical liquids. IJPC. 1999;3:146-147.
3. Allen LV Jr. Remington: The Science and Practice of Pharmacy. 22nd ed. London, England: Pharmaceutical Press; 2012:1446.
4. Myambutol. www.rxlist.com/myambutol-drug.htm. Accessed June 6, 2017.
5. Ethambutol. www.drugs.com/pro/ethambutol.html. Accessed June 6, 2017.
6. Ora-Plus product information. Allegan, MI: Perrigo; 2014.
7. Ora-Sweet SF product information. Allegan, MI: Perrigo; 2014.

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