What Are the Different Types of Intravenous Antibiotics?

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  • Written By: Amanda Livingstone
  • Edited By: Jessica Seminara
  • Last Modified Date: 18 August 2019
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Intravenous antibiotics can be separated into three groups, which are gram-positive, gram-negative and broad spectrum antimicrobial medications. Gram-positive antibiotics, which include glycopeptides, are medications that target bacteria with a thick cellular wall. In contrast to gram-positive antibiotics, gram-negative antimicrobial agents such as aminoglycoside and polymxin target bacteria that contain a thin cellular wall. Broad spectrum intravenous antibiotics, including cephalosporin and penicillin, target both types of bacteria.

Glycopeptide class antibiotics are generally composed of peptide enzymes that inhibit synthesis of microbe cell walls. Due to a high level of toxicity, use is restricted to critically ill patients. Vancomycin is a common intravenous glycopeptide antibiotic that is often used to treat a serious intestinal infection called Clostridium difficile-associated diarrhea. This gram-positive intestinal infection usually requires vancomycin to be administered slowly over a daily period of one to two hours. Dosage will largely depend on the patient's condition, weight and kidney function.

Aminoglycoside class antibiotics are primarily useful for treating aerobic and gram-negative infections, such as Escherichia coli (E. coli). Intravenous tobramycin is an aminoglycoside that is used to treat various forms of E. coli. The drug works by stopping the offending microbes. Similar to glycopetide class antibiotics, tobramycin has been shown to be extremely toxic to the kidneys and nerves.


Unlike other classes of antimicrobials, polymyxin antibiotics such as colistin are generally not administered orally. Polymyxin, which is a gram-negative bacterium typically, comes in inhaled or intravenous form. Intravenous antibiotics including colistin are often used against severe drug resistant bacterial infections usually involving the intestinal, pulmonary and urinary tract structures.

Compared to gram-negative and positive specific antibiotics, cephalosporin and penicillin class antimicrobials treat a wider range of infections. Infectious conditions such as meningitis and drug-resistant bacteria are often treated with the broad-spectrum antibiotics. Ampicillin is a synthetic form of penicillin that is commonly prescribed for various conditions, including meningitis. When taking ampicillin patients should look out for severe side effects such as bloody stools, severe abdominal pain and cramping.

All forms of intravenous antibiotics are given through a vein or muscle. Injecting antibiotics directly into the blood stream helps to speed-up the medication’s effects. Administering antibiotics through the intravenous method also gives the patient an uninterrupted dose of medication. Another advantage of intravenous antibiotic therapy over oral administration is the ability to bypass the gastrointestinal tract. Oral antibiotics can kill the “good” bacteria found in the gastrointestinal tract leading to diarrhea, fungal infections and the proliferation of “bad” bacteria.


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Post 1

I had IV antibiotics when I had a fever after a C-section birth. I'm not sure what kind they were. What bothered me was that my doctors couldn't agree on anything! First, I was on just one antibiotic as a precaution. Then, the next day I still had a fever, so I was changed to *three* different ones! I was supposed to be on them for forty-eight hours.

But you know how it is - it was the weekend, and the next day I had a different doctor. He said that all those antibiotics were overkill and could cause side effects, so he just turned them off when I hadn't finished the course of treatment yet.

Well, if I didn't need them, why was I on them in the first place? It's frustrating to me that doctors don't have more clear protocols about when you do and don't need treatment of various kinds.

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