Neomycin, pronounced as (nee oh mye' sin), is a broad-spectrum oral antibiotic. Neomycin must be prescribed by a doctor, and it is not available as an over-the-counter (OTC) product.  

Neomycin sulfate is the most common pharmaceutical product available. This antibiotic can be used in combination with other medications in treating hepatic coma and preventing bacterial infection in the intestines. As an antibiotic, neomycin is used for certain bacterial infections. It doesn’t work against viral infections such as colds and flu.  

Neomycin belongs to a class of antibiotics called aminoglycosides. This class of antibiotics is particularly active against Gram-negative bacteria; they have weak coverage against Gram-positive bacteria if used alone. Thus, they are often used in combination with other antibiotics for synergistic coverage against Gram-positive infection. 

Neomycin Uses

Neomycin oral tablets are used to prevent intestinal bacterial infections and treat the following medical conditions:

Hepatic Coma

Also called hepatic encephalopathy (HE), hepatic coma is an altered level of consciousness due to liver failure.

In a hepatic coma, ammonia levels rise in the blood and could pass the blood-brain barrier in the brain. The blood-brain barrier (BBB) protects the brain from toxic substances in the blood. BBB provides nourishment to the brain tissue and also filters harmful substances. High concentrations of ammonia passing the BBB can cause neuronal damage, leading to hepatic coma or neuronal edema. The bactericidal effect of neomycin can decrease the high levels of ammonia by reducing the ammonia-forming bacteria in the intestines. Neomycin is used in combination with other medications for the treatment of hepatic coma.

Surgical prophylaxis

Neomycin is often used as a surgical prophylaxis. It is taken prior to colorectal surgery to prevent intestinal infection caused by the normal bacteria flora of the bowel.

Digestive Issues

Neomycin is also used off-label to treat constipation-predominant irritable bowel syndrome (IBS-C). 

Other forms of neomycin

Ear infections

Neomycin with active ingredients of polymyxin B sulfates and hydrocortisone is available as an otic suspension (ear drop). It is used to treat surface-level bacterial infections in the outer ear. 

Eye conditions

Neomycin is available as an ophthalmic solution (eye drop) used for eye-related infections. Its active ingredients include neomycin, polymyxin B sulfates, and dexamethasone.

Skin infections

Neomycin is also used to prevent or treat skin infections caused by bacteria. However, it is usually not effective against any type of fungal or viral infection.

How does Neomycin work?

Neomycin belongs to a group of antibiotics known as aminoglycosides. As a group, aminoglycosides are very active against Gram-negative infections and are often used with other antibiotics to treat certain Gram-positive infections. Neomycin and other aminoglycosides kill bacteria by interfering with bacterial protein synthesis, which is essential for the bacteria to survive and multiply. 

When being used before bowel surgery, neomycin helps eradicate the gut bacteria to prevent intestinal bacterial infection.  

When used as part of a combination regimen to treat hepatic coma, neomycin kills the ammonia-forming bacteria. As a result, it helps alleviate the symptoms caused by this health condition.  

How should you take Neomycin?

Neomycin is an active ingredient of other products such as topical medication, eye drops, and ear drops; keep in mind that this article focuses on the information of neomycin oral tablets. 

Neomycin can be taken with or without food. If you're using the liquid form of neomycin, be sure to measure each dose carefully using an oral syringe or medicine measuring cup. Household items such as kitchen teaspoons will not provide an accurate measurement of medication dosage.

Dosage guidelines For oral administration

Pediatric use: The safety and efficacy of oral neomycin sulfate have not been established in patients less than 18 years old. If the treatment of oral neomycin is necessary for a patient less than 18 years of age, neomycin should be used with caution. The dosage of neomycin will be determined by the physician based on body weight and the condition being treated. The duration of treatment should not exceed two weeks. 

For patients who are in a coma due to liver disease 

• Adults (18 to 64 years old) should take 1 to 3 grams every six hours or a total of 4 to 12 grams daily for five to six days.

Preparation for bowel surgery

• Adults (18 to 64 years old) should take 1 gram every hour for four hours, then 1  gram every four hours for the remainder of the twenty-four-hour period; or the alternative regimen is to take 1 gram at 19 hours, 18 hours, and 9 hours before the start of surgery.

Interactions and Considerations

Interaction can modify how a particular drug acts on the body. These interactions can be hazardous or can stop the medication from working properly. The following are other drugs, supplements, and substances that can interact with neomycin:

Multivitamins

This medication may reduce vitamin B6, vitamin B12, vitamin D, folate, or iron levels. While using this medication, you should ensure that you are taking enough vitamins. It can also deplete or reduce calcium, carbohydrates, lipids, magnesium, potassium, beta carotenes, salt, and vitamins A and K.

Talk to your health care professional about what vitamins you should supplement while taking neomycin.

Alcohol or tobacco

Alcohol and tobacco use can cause interactions when taking neomycin. Do not drink alcohol while you are taking neomycin to reduce your risk of serious problems and side effects. 

Food

Avoid high-protein food if you are receiving neomycin therapy. 

Over-the-counter drugs (OTCs) 

Neomycin can interact with PPIs (proton pump inhibitors), such as pantoprazole, and  NSAIDs, such as celecoxib, ketorolac, and over-the-counter ibuprofen or naproxen.

Anti-cancer drugs

Chemotherapy such as methotrexate and fluorouracil can interact with neomycin, leading to kidney injury. Let your doctor know if you are receiving any type of cancer treatment. 

Organ transplant medicine 

Neomycin can interact with immunosuppressants, such as tacrolimus and sirolimus. This interaction can harm your kidneys. Let your doctor know if you are taking medication for organ transplant rejection. 

Antibiotics

Neomycin can interact with certain antibiotics, including cephalosporins.

Tell your doctor if you are taking vitamins, herbs, dietary supplements, or other medicines, as oral neomycin may cause an interaction. Your health care professional will closely monitor all the medicines you are taking to prevent interactions. 

Ask your doctor or pharmacist about how this medication may interact with all your medications.

What are the special considerations while taking neomycin?

The oral tablet of neomycin is meant to be taken for a short period of time. Follow the instructions given by your doctor carefully about how to take this medication.

Consistent medication use

If you suddenly stop taking the pill or forget a dose, your infection may worsen. 

Missed dose

If you miss a dose or don't take the tablet on time, it could lessen its effectiveness. In case of a missed dose, you should take the missed dose as soon as you remember. However, if it is almost time for your next dose, take only that dose and skip the missed dose. Do not take twice the amount to make up for the missed dose, as this can cause serious side effects. 

Complete medication course

It's important to complete the entire course of medicine and follow instructions given to you by your health care professional. Don't stop taking the medicine before the course is completed or skip doses even if you start feeling better. Doing so could make it harder to treat the infection.

Overdose 

Since your body doesn't absorb a lot of this medication, you’re unlikely to overdose. However, too much neomycin can damage the kidneys, ears, and nervous system. If you think you have taken more than the recommended dose of neomycin, contact your health care professional or call the Poison control center immediately.

Side Effects and Precautions

Common Side Effects

• Upset stomach
• Nausea
• Vomiting
• Diarrhea

If these side effects last more than a few weeks, visit your health care professional or consult your pharmacist.

Serious side effects

If you experience any of the side effects listed below, tell your doctor immediately:

Neurological or brain damage

Signs of neurological or brain damage include:

• Numbness
• Itching skin
• Muscle straining
• Shaking
• Hearing impairment and ear damage

Kidney problems

Possible side effects due to kidney problems include:

• Confusion
• Fatigue
• Thirst
• Urinating less frequently than usual
• Muscle tremor
• Breathing issues

Precautions and warnings

Read the precautions on the prescription label before taking this drug. 

Allergic reaction

Tell your doctor immediately if you experience any of the following life-threatening signs of an allergic reaction: 

Anaphylactic allergic reaction can happen in some cases. You must seek emergency medical attention if you experience the following signs: difficulty breathing, hives, rash, swelling of the face, tongue, lips, or throat.

Neomycin may not be the best option for everyone. Tell your doctor if you have any of the following conditions as taking neomycin could potentially worsen it: 

• Gut problems such as inflammatory or ulcerative intestinal disease 
• Muscle weakness such as myasthenia gravis and Parkinson's disease

During pregnancy

Neomycin is typically considered not safe for pregnant women as it can cause birth defects. This medicine should only be prescribed to pregnant women when healthcare professionals decide it is necessary to treat a dangerous condition.

If you are pregnant or plan to become pregnant, consult your doctor. This medicine should only be taken by pregnant women if the benefits outweigh the potential risks. 

Breast feeding mothers

Neomycin may transfer into breast milk and generate adverse effects on the baby. If you are breast feeding or plan to start, consult your doctor, as they may decide to put you on a different medication. 

When to seek medical attention

Seek immediate medical attention, and tell your doctor if you experience the following: 

• Severe allergic reactions
• Rash, itching, or skin irritation
• Hearing loss or balance issues
• Kidney problems
• Neurological symptoms
• Antibiotic-associated colitis or diarrhea
• Vision Changes
• Difficulty swallowing or breathing

Consulting with a healthcare professional is important while having these symptoms, as they will determine the appropriate course of action.

References

• https://www.ncbi.nlm.nih.gov/books/NBK560603/#article-25650.s2 
• https://go.drugbank.com/drugs/DB00994 
• https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/neomycin