Gentamicin

METHOD OF PREPARATION

Notes: This preparation should be done in a laminar airflow hood in a cleanroom or via isolation barrier technology by a validated aseptic compounding pharmacist using strict aseptic technique. When compounding from the bulk powder, the labeled activity of the lot must be used in the calculations for obtaining the required quantity of gentamicin sulfate.

1. Calculate the required quantity of each ingredient for the total amount to be prepared.

2. Accurately weigh and/or measure each ingredient.

3. Dissolve the powders in sufficient sterile water for irrigation to volume.

4. Sterile filter through an appropriate sterile 0.2-µm filter into sterile containers.

5. Package and label.

PACKAGING

Package in tight, light-resistant containers.1

LABELING

Keep out of reach of children. Use only as directed.

STABILITY

If prepared from nonsterile powders and no sterility testing is done, a beyond-use date of 24 hours at room temperature, 3 days at refrigerated temperature or 45 days at

USE

This solution is used as a bladder irrigation in the treatment of susceptible microorganisms.

QUALITY CONTROL

Quality-control assessment can include weight/volume, physical observation, pH, specific gravity, osmolality, assay, color, clarity, particulate matter, sterility and pyrogenicity.2,3

DISCUSSION

Many different formulations are commonly used for the treatment of bladder infections via instillation of a solution of antibiotics.

Gentamicin sulfate is an aminoglycoside antibiotic occurring as the sulfate salt, or a mixture of such salts, of the antibiotic substances produced by the growth of Micromonospora purpurea. Commercially, it is a mixture of the sulfate salts of gentamicin C^sub 1^, C^sub 2^ and C^sub 1A^. It occurs as a white-to-buff-colored powder that is soluble in water but insoluble in alcohol. The pH of the injection is between 3.0 and 5.5. It has a potency equivalent of not less than 590 µg of gentamicin per mg calculated on the dried basis. It should be preserved in tight containers.1,4

Neomycin sulfate is an aminoglycoside antibiotic obtained from cultures of Streptomyces fradiae. It occurs as a white-to-slightly yellow, hygroscopic powder that is freely soluble in water and very slightly soluble in alcohol. It should be stored in tight, light-resistant containers. Neomycin sulfate has a potency equivalent of not less than 600 µg of neomycin per mg, calculated on the dried basis.1,4

Polymyxin B Sulfate is the sulfate salt of a polymyxin produced by the growth of Bacillus polymyxa. It occurs as a white-to-buff-colored, hygroscopic powder that is odorless or has a faint odor. It is freely soluble in water and in 0.9% sodium chloride injection and slightly soluble in alcohol. It has a potency of not less than 6000 Polymyxin B units per mg, calculated on the dried basis. Each mg of pure polymyxin B is equivalent to 10,000 units of polymyxin B activity. Its aqueous solutions have a pH of 5-7.5.1,4

Sterile water for irrigation is prepared from water for injection that is sterilized and suitably packaged. It contains no antimicrobial agent or other added substance. It should be preserved in single-dose glass or plastic containers. Containers are preferably of Type I or Type II glass. The container may contain a volume of more than 1 L, and may be designed to empty rapidly. The designations "For irrigation only" and "Not for injection" appear prominently on the label. It contains not more than 0.25 endotoxin unit per mL. It occurs as a clear, colorless, odorless liquid.

REFERENCES

1. US Pharmacopeial Convention, Inc. United States Pharmacopeia 27-National Formulary 22. Rockville, MD: US Pharmacopeial Convention, Inc.; 2004: 859-860, 1288, 1506-1507, 1950, 2345-2349.

2. Allen LV Jr. Standard operating procedure for particulate testing for sterile products. IJPC 1998; 2: 78.

3. Allen LV Jr. Standard operating procedure: Quality assessment for injectable solutions. IJPC 1999; 3: 406-407.

4. McEvoy GK. AHFS Drug Information-2000. Bethesda, MD: American Society of Health-System Pharmacists; 2000: 70-74, 458-460.

Copyright International Journal of Pharmaceutical Compounding Nov/Dec 2004
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