Polymyxin B Sulfate And Trimethoprim: Uses, Side Effects

Polymyxin B sulfate and Trimethoprim is an ophthalmic combination that is used to treat eye infections. They treat bacterial infections of the eye including conjunctivitis (also popular as pink eye) or blepharoconjunctivitis. While polymyxin B sulphate works by killing the bacteria, trimethoprim works by stopping the growth of the bacteria

Polymyxin B sulfate works by affecting the bacterial cell wall structure that causes the leaking of cellular contents and cell death. In contrast, trimethoprim intervenes with the production of tetrahydrofolic acid; it is a necessary chemical for bacteria cells to produce proteins. It inhibits the growth of tetrahydrofolic acid by inhibiting the enzyme that makes tetrahydrofolic acid from dihydrofolic acid. This effect affects the survival chance of the bacteria.

If you are curious enough to learn more about polymyxin b sulfate and trimethoprim ophthalmic solution, here is an amazing read. The blog discusses all the important details of the ophthalmic solution. Know all the details properly before you start to use the eye- drops.

What Are Polymyxin B Sulfate and Trimethoprim Used For?

Polymyxin B Sulfate and Trimethoprim Ophthalmic Solution

Source: amconlabs.com

You can use this medicine for treating the bacterial infection that occurs in the eye. It contains two antibiotics. Polymyxin B sulfate kills the bacteria, and Trimethoprim works by stopping the bacteria from growing.

Keep in mind that this medicine treats bacterial eye infections and won’t work for another type of eye infection. Improper use of the medication can drastically decrease its effectiveness rate.

What Are the Warnings and Precautions Associated with Polymyxin B Sulfate and Trimethoprim?

polymyxin b sulfate and trimethoprim ophthalmic solution

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If you are new to using polymyxin b sulfate and trimethoprim ophthalmic solution, it is important to be well aware of all the warnings and precautions while using the drug. Here is a quick sneak peek at the list of the warnings and precautions associated with the solution:

  • You should not use this medication if you’re allergic to either polymyxin or Trimethoprim. 
  • If you are pregnant or planning to conceive, you should avoid using this medicine as this medicine is harmful to the unborn baby. Consult the doctor if you have become pregnant during the use of medication. Also, if you are a breastfeeding mother, it is best to tell your doctor about it because it is still unknown whether the medicine can pass through breast milk or not.
  • Keep this medicine out of the reach of children and do not give it to someone younger than two months old. Many containers, such as pill minders and eye medications, are not child-resistant, and young children can easily open them.

Points To Keep In Mind:

  • Make sure to tell your doctor if you have or ever had any other medical health condition. Remember that bacterial conjunctivitis spreads quickly; wash your hands often, especially after touching your eyes. You should replace any eye products that touch the infected eye when your treatment is completed, such as makeup and contact lenses.
  • Don’t use this medicine if the liquid color of the medicine changes or has particles in it; if you see this, you should get a new medicine.
  • Keep the medicine at room temperature; different brands of this medicine have different storage needs. Ensure that you read the package instructions on how to store the medicine. 
  • Do not keep it in the refrigerator and keep it out of the reach of pets and children.
  • You should not flush the medicine down the toilet or pour it into a drain unless the doctor approves it. Discard the medication properly when it reaches its expiration date, or you do not need it.
  • Don’t give this medicine to anyone else without consulting the doctor because your medical condition and other person’s condition may vary, and it can cause severe side effects. It is essential to keep a written list of prescribed and non-prescribed medication you may be having. This also includes vitamins, minerals, and other dietary supplements. Bring the list to the doctor each time you visit or if you are admitted to a hospital.

How to Use Polymyxin B Sulfate and Trimethoprim?

polymyxin b sulfate and trimethoprim ophthalmic solution

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To use this medicine, make sure to wash your hands. Don’t touch the tip of the medication or let it touch the eye or other surface to avoid contamination. It is an eye drop, do not swallow it or inject. Also, you should not use this medicine while using contact lenses. Sterilize contact lenses according to the manufacturers’ instructions and consult with the doctor before you begin to wear them again.

Your doctor will prescribe your dosages based on your health condition and response to treatment; initially, your primary health care provider may tell you to use this medicine more often, then reduce the use as the infection improves. Carefully follow the doctor’s direction.

Usually, it is prescribed to use it for 7-10 days. Stopping the medication too soon or suddenly may allow the bacteria to continue to grow, resulting in the infection’s return.

Look upward, tilt your head back and pull down the lower eyelid that works like a pouch. Now you must hold the dropper right over the eye and, as directed by the doctor, drop the pouch. Look downward, close your eyes gently, and put your finger at the eye corner.

Gently apply the pressure for 1-2 minutes before opening the eyes. It will prevent the medicine from draining out. Try not to rub or blink the eye. Repeat these steps if the dose is more than one drop.

If you have to use this medicine for both eyes, repeat these steps for the other eye. Wait for several minutes for your vision to clear before operating heavy machinery or driving. Replace the dropper cap after each use, and do not rinse the dropper.

Things To Know:

You should also avoid other unnecessary eye products for example beauty ointments, drops, artificial tears while using these eye drops. Some properties in the products may interact with the medication and prevent it from providing its effects. You should also contact your doctor about using other eye products while using this eye medicine and how long you have to wait before applying the other products. It would be best to use eye drops before eye ointments- one that is prescribed by the doctor because they will allow the drops to enter the eye.

Your symptoms should improve while using the medicine; contact your physician if your symptoms do not improve or worsen or if you feel that you have other eye problems during the treatment.

Keep using this medicine until you complete the prescription, even if you feel better. If you stop the medication use too soon, your symptoms may get reversed, and the bacteria may become resistant to antibiotics.

What Are the Dosages of Polymyxin B and Trimethoprim?

polymyxin b sulfate and trimethoprim ophthalmic solution

Source: news18.com

Usual Adult Dose for Bacterial Conjunctivitis:

Use one drop in the affected eye in the gapping of 3 hours for 7-10 days. The maximum dose for a day is six doses.

Usual Adult Dose for Blepharoconjunctivitis:

You should use one drop in the affected eye every 3 hours for 7-10 days.

Key-tip: The actual dosage varies depending upon the severity of the infection. You need to take it only once or twice a day if there is only a mild infection. However, for severe cases, the dosage may go as high as seven times a day.

What to Do If I Miss a Dose?

If you happen to miss the dose, make sure to use it as soon as you remember it, but skip it if it is time for the upcoming dose. It is harmful to use double to make up for the missed dose.

What Other Medicines May Interact with Polymyxin B and Trimethoprim?

Some medicine’s effects may interact with the drops; it can also reduce the risk of severe side effects or cause the medicine not to work effectively. These medicine interactions are possible but do not necessarily occur.

Your doctor can reduce the risk of drug interactions by changing how you use your medicine. Take the help of your doctor by telling him about all the products you use and herbal products before using this medicine. While using this medicine, use it according to the doctor’s guidance, do not stop or change the dosage of any medication you are using without consulting with the doctor first.

Also Read: 6 Best Food For Eyes: Edibles That Improve Your Eyesight

What Are the Side Effects of Polymyxin B and Trimethoprim?

Seek immediate assistance if you have any signs: hives, breathing difficulty, or swelling of the face, lips, or tongue. Do not take this medicine if you feel the following symptoms:

  • Eye pain, redness, severe discomfort, and swelling
  • Drainage or crusting (may be signs of infection)
  • Redness or swelling of the eyelids
  • Worsening symptoms.

Common side effects may include:

  • Stinging
  • Mild burning
  • Itching of the eyes

Key-note: If the common symptoms mentioned above remain persistent for a long time after dosage, you must first consult the doctor before using the eye drops


Polymyxin B sulfate- Trimethoprim ophthalmic solution works in combination to cure bacterial eye infections. The above article discussed the drugs in detail. You must be well familiar with all the side effects and drug interactions before you start using these drops. Know the proper dosage and storage information before using this medication.

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