What is the color of gentamicin? Understanding a Medication's Appearance

October 6, 2025 •

3 min read

According to the National Institutes of Health, gentamicin sulfate is a white to buff-colored powder, but its color can vary based on its final pharmaceutical formulation. Understanding what is the color of gentamicin in its different forms is crucial for patient and professional safety, as any change could indicate degradation.

Quick Summary

The color of gentamicin depends on its form: the powder is white to buff, while the solution is clear and colorless to pale yellow. A noticeable color change can indicate degradation, warranting its disposal for safety reasons.

Key Points

Gentamicin Powder is White to Buff: The raw gentamicin sulfate is a hygroscopic powder that is typically white to buff-colored.
Gentamicin Solution is Clear: The injectable or ophthalmic solution is a clear liquid that can range from colorless to a faint yellow.
Color Change Signals Degradation: Any significant darkening, cloudiness, or precipitation in the solution is a warning sign of degradation and renders the medication unfit for use.
Storage Affects Stability: Proper storage away from excessive heat and light is crucial for maintaining the color and chemical stability of gentamicin.
Verify Appearance Before Use: Before administering, always visually inspect the medication to ensure its appearance matches the expected coloration to prevent potential adverse effects.

The Different Forms and Their Colors

Gentamicin is a broad-spectrum antibiotic used to treat various serious bacterial infections. Its appearance is not uniform across all products because it is available in different preparations, such as a powder for reconstitution, an injectable solution, and topical applications like ophthalmic drops. Each form has a distinct, normal coloration, and knowing these details is important for quality control and medication safety.

The Color of Gentamicin Powder

In its raw form as a hygroscopic powder, gentamicin sulfate typically appears white to off-white. Some descriptions may also include the term "buff-colored" to describe its appearance. This powdered form is primarily used in industrial or laboratory settings for the preparation of sterile solutions or other formulations. This can include preparing products for mammalian cell culture, where the gentamicin is a white to off-white powder. Its appearance is stable as a powder when stored correctly in an airtight container. As with many compounds, the color is the result of its chemical structure and the presence of any trace impurities from the manufacturing or fermentation process.

The Color of Gentamicin Solutions

When gentamicin sulfate powder is dissolved in water to create a solution for injection or ophthalmic drops, its color profile changes dramatically. The final solution is generally described as clear and colorless to faint or light yellow.

Gentamicin Injection (Parenteral Use): Vials and ampoules for intravenous or intramuscular administration contain a sterile solution that is typically clear and colorless, or almost colorless. The concentration of the solution can have a slight impact on the intensity of the pale yellow hue.
Gentamicin Ophthalmic Solution (Eye Drops): Formulations for eye drops are also clear. They range from colorless to a pale straw or faint yellow color. The specific concentration and inactive ingredients included by the manufacturer can influence this slight color variation.

What a Color Change Can Indicate

Any unexpected change in the appearance of a gentamicin product is a critical sign that it should not be used. A significant color change often indicates that the medication has undergone degradation or contamination, potentially rendering it ineffective or unsafe.

Visible signs of degradation include:

Darkening of the solution: A solution that has become dark yellow, brown, or discolored from its original colorless or pale yellow state may be compromised.
Cloudiness or precipitation: The presence of particles, haze, or caking in a solution that should be clear is a clear sign of instability.
Presence of visible particles: Particulate matter in a sterile solution is an immediate cause for concern and warrants disposal.

Such changes can be caused by exposure to heat, light, or air, or by simply being past the expiration date.

Factors Influencing the Color and Stability

While the base color of gentamicin is predictable, a few factors can cause slight variations or signal potential issues.

Comparison of Gentamicin Forms and Characteristics


Feature	Powder Form (Sulfate Salt)	Solution Form (Injection/Ophthalmic)
Appearance	White to off-white or buff-colored powder.	Clear and colorless to pale yellow liquid.
Solubility	Freely soluble in water.	Already dissolved in water for injection.
Hygroscopicity	Hygroscopic (absorbs moisture).	Not applicable, already in solution.
Stability	Relatively stable when stored properly.	Stability can be affected by light, heat, and air over time.
Indications of Degradation	Caking or visible discoloration of the powder.	Darkening, cloudiness, or precipitation.

For medication safety, consider the following:

Storage conditions: Gentamicin should be stored according to manufacturer instructions, typically in a cool, dark place, to prevent degradation.
Expiration date: The expiry date is a critical factor. Even if the medication appears visually normal, its potency may have decreased after expiration.
Original packaging: The container can play a role in stability. Some formulations are packaged in light-protected containers to prevent photo-degradation.

Conclusion

In summary, the color of gentamicin is not a single, fixed attribute but depends on its pharmaceutical preparation. The powdered sulfate form is white or off-white, while the solution for injection or eye drops is clear and can range from colorless to a faint yellow. The subtle variation within the solution is normal, but a significant deviation, such as darkening or cloudiness, is an unmistakable warning sign of degradation. Always inspect your medication for its proper appearance and discard any product with a suspicious color change or visible particles to ensure your safety and treatment efficacy, based on information from the National Library of Medicine.

Frequently Asked Questions

Gentamicin sulfate powder is typically white to buff-colored. Slight variations in shade can occur, but it should be consistent across batches from the same manufacturer.

A gentamicin injection that has turned dark yellow is a sign of degradation. The medication should be clear and colorless to pale yellow. A dark color indicates it is no longer safe or effective to use.

Yes, over time, and particularly after the expiration date or due to improper storage, the color of a gentamicin solution can change. This often indicates chemical instability.

The injectable and ophthalmic solution forms of gentamicin should be clear. They can be colorless to a faint yellow, but they should not be cloudy or contain any particles.

Gentamicin eye drops are a clear solution that is typically colorless to a pale straw or faint yellow color. This is considered normal for the product.

If you notice a change in the color of your gentamicin medication, or if it develops cloudiness or particles, you should discard it immediately and not use it. Consult your pharmacist or healthcare provider for a replacement.

Yes, gentamicin solutions can become cloudy or develop visible particles, known as precipitation, if they have expired or degraded. The presence of any such changes means the medication should not be used.