Merck Manual

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Polypeptides

By

Brian J. Werth

, PharmD, University of Washington School of Pharmacy

Last full review/revision Jun 2022| Content last modified Jun 2022
CLICK HERE FOR THE PROFESSIONAL VERSION
Topic Resources
  • Bacitracin

  • Colistin

  • Polymyxin B

Most bacteria have an outer covering (cell wall) that protects them. Bacitracin works by preventing bacteria from forming this wall. Colistin and polymyxin B work by disrupting the cell membrane underlying this wall in some bacteria. As a result, the bacteria die.

Colistin and polymyxin B commonly cause kidney damage, so they are used only for serious infections in which bacteria are resistant to all other antibiotics and no safer alternatives are available. When colistin or polymyxin B is used, it is given by vein (intravenously). In some cases, colistin may be inhaled through a nebulizer.

Table

Polypeptides

Drug

Common Uses

Some Potential Side Effects

Bacitracin

Colistin

Polymyxin B

Ear, eye, or skin infections

Bladder infections (polymyxin B may be used for bladder irrigation)

Serious infections caused by susceptible bacteria that are very resistant to many other antibiotics (colistin and polymyxin B given by injection)

Kidney and nerve damage (when given by injection)*

* Polypeptide antibiotics are usually applied directly to the ears, skin, or eyes, but colistin and polymyxin B are sometimes given by injection when bacteria are resistant to all other antibiotics and no safer alternatives are available. Bacitracin is not available for injection.

Use of Polypeptides During Pregnancy and Breastfeeding

With bacitracin, the risk to the fetus during pregnancy and to the newborn during breastfeeding is thought to be slight because bacitracin is applied topically and little of the drug is absorbed Drug Absorption Drug absorption is the movement of a drug into the bloodstream after administration. (See also Introduction to Administration and Kinetics of Drugs.) Absorption affects bioavailability—how quickly... read more into the bloodstream. However, its safety has not been established. The same is true for polymyxin B and colistin when they are applied topically.

Polymyxin B and colistin should be taken by injection during pregnancy only when the benefits of treatment outweigh the risks. With polymyxin B, no harmful effects on the fetus have been observed in animal studies, but no well-designed studies have been done in pregnant women. With colistin, harmful effects on the fetus have been observed in animal studies. (See also Drug Use During Pregnancy Drug Use During Pregnancy More than 50% of pregnant women take prescription or nonprescription (over-the-counter) drugs or use social drugs (such as tobacco and alcohol) or illicit drugs at some time during pregnancy... read more .)

Drugs Mentioned In This Article

Generic Name Select Brand Names
BACIIM
No US brand name
NOTE: This is the Consumer Version. DOCTORS: CLICK HERE FOR THE PROFESSIONAL VERSION
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