Colistimethate is an antibiotic used to treat certain bacterial infections. It works by stopping the growth of bacteria.

This section contains uses of this drug that are not listed in the approved US professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

In people with cystic fibrosis, inhaled colistimethate may also be used for serious bacterial lung infections (Pseudomonas aeruginosa). See also Storage section for information about important safety concerns when this medication is inhaled.

Colistimethate for injection is usually given into a vein or a muscle as directed by your doctor. The dosage is based on your medical condition and response to treatment.

If you are giving this medication to yourself at home, learn all preparation and usage instructions from your health care professional. Before using, check this product for particles or discoloration. If either is present, do not use the liquid. Learn how to store and discard medical supplies safely.

If you are inhaling this medication, learn how to prepare the solution and use the nebulizer machine properly. See also the Storage section. If you have any questions, ask your health care professional.

For the best effect, use this antibiotic at evenly spaced times. To help you remember, use this medication at the same time(s) every day.

Continue to use this medication until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping the medication too early may result in a return of the infection.

Tell your doctor if your condition does not get better or if it gets worse.

Stomach upset and itching may occur. If either of these effects lasts or gets worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• numbness/tingling (especially of the arms/legs, around the mouth/tongue)
• strange feeling on the skin of the arms/legs
• mental/mood changes (such as confusion, psychosis, seizures)
• difficulty walking
• unsteadiness
• slow/shallow/troubled breathing
• dizziness/feeling of spinning
• unexplained fever
• trouble speaking
• muscle weakness
• signs of kidney problems (such as change in the amount of urine)
• red/pink urine

This medication may rarely cause a severe intestinal condition due to a bacteria called C. difficile. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop:

• diarrhea that doesn't stop
• abdominal or stomach pain/cramping
• blood/mucus in your stool

If you have these symptoms, do not use anti-diarrhea or opioid products because they may make symptoms worse.

Use of this medication for prolonged or repeated periods may result in a new infection. Tell your doctor if you notice any symptoms of a new infection (such as white patches in your mouth, a change in vaginal discharge).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using colistimethate, tell your doctor or pharmacist if you are allergic to it; or to polymyxin B or colistin; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• diseases of the nerves/muscles (such as myasthenia gravis)
• kidney disease

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery or any procedure requiring anesthesia or medications that block nerve or muscle activity, tell your doctor or dentist that you are using this medication.

This medication may cause live bacterial vaccines (such as typhoid vaccine) to not work well. Tell your health care professional that you are using this medication before having any immunizations/vaccinations.

Older adults may be more sensitive to the side effects of this drug, especially kidney problems.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• cephalothin

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: extreme drowsiness, slow/shallow breathing, muscle weakness, inability to move.

Lab and/or medical tests (such as kidney function) should be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

It is important to get each dose of this medication as scheduled. If you miss an injection, ask your doctor or pharmacist right away for a new dosing schedule. Do not double the dose to catch up.

If you miss an inhaled dose, use it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Use your next dose at the regular time. Do not double the dose to catch up.

For colistimethate injection, consult the product instructions and your pharmacist for storage details.

If you are using colistimethate as an inhalation, store the unmixed vials at room temperature. Do not use premixed solution or prepare the solution ahead of time because this increases the risk of very serious breathing problems. Prepare the inhalation solution right before use. Discard any unused solution after 24 hours. Do not store for longer periods. Ask your health care professional for details.

Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.