What Is the Connection between Metronidazole and Amoxicillin?

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  • Written By: B. Chisholm
  • Edited By: O. Wallace
  • Last Modified Date: 10 August 2019
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Metronidazole and amoxicillin are both antibiotics that belong to different classes, work in different ways and are effective against different bacterial infections. The choice between using the two will be made by the prescribing doctor after diagnosis. They are both available in various pharmaceutical forms known by different trade names in different countries, according to manufacturer.

Amoxicillin belongs to the class of drugs called penicillins. It is a broad spectrum antibiotic, which means that it is active against a wide range of bacteria, including gram-positive and gram-negative bacteria. Some resistance has developed and to combat this, amoxicillin is often given in combination with clavulanic acid. It works by interrupting cell wall synthesis of the bacteria. Amoxicillin is used to treat many infections including otitis media, sinusitis and lower respiratory tract infections.

Metronidazole is a nitroimidazole derivative which has antiprotozoal and antibacterial activity. It works by interfering with the bacterial DNA. The most common indications for its use include anaerobic bacterial infections, amoebic dysentery, periodontal infections, giardiasis and trichomoniasis. When using metronidazole to treat an infection, alcohol should be avoided completely, as a potentially dangerous interaction may occur if using them together.


As with any medication, both metronidazole and amoxicillin may interact with other drugs. This includes complementary, homeopathic and over-the-counter medications, all of which should be disclosed to the prescribing doctor. Other underlying clinical conditions, pregnancy, desired pregnancy and lactation should also be discussed with the doctor, as these may affect the choice of antibiotic prescribed.

Adverse reactions may occur with metronidazole and amoxicillin. Both may cause gastrointestinal side effects such as nausea, vomiting, abdominal pain and diarrhea. Metronidazole may cause headache, other central nervous system (CNS) effects such as confusion or dizziness or a metallic taste in the mouth. Should any unwanted or severe adverse effects be experienced, medical attention should be sought.

Both drugs are available in various pharmaceutical forms including oral and injectable formulations. The choice of which to use will be made clinically but is, most often the oral form. The dose and duration of treatment will also be decided by the prescribing doctor according to the infection being treated and the severity thereof. On occasion, especially when treating dental infections, metronidazole and amoxicillin may be prescribed together.

The prescribed dosage should be adhered to and the course completed, even if all symptoms resolve prior to finishing the course. Stopping before the end of the course may result in resistant bacteria and difficulty treating, should another infection occur. This applies to any course of antibiotics.


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Post 4

@JaneAir - You're right. Plus, metronidazole side effects are unpleasant enough without increasing them by drinking. The last time I took metronidazole it really bothered my stomach, and it left a metallic taste in my mouth. I think I chewed gum almost the whole time I was on it, and it barely helped!

Post 3

Mixing alcohol with most antibiotics is a pretty bad idea. I've never mixed alcohol with metronidazole, but I have mixed it with another antibiotic that I wasn't supposed to.

I ended up with horrible stomach symptoms pretty quickly after I had one drink! It was horrible. I've never mixed alcohol with antibiotics since then! Plus, drinking when you're sick is a bad idea anyway, because alcohol can lower your immune system. So it's better to just not do it!

Post 2

@betterment - Even though metronidazole and amoxicillin both treat bacterial infections, it seems like they treat different things. So they aren't exactly interchangeable! However, there are tons of other antibiotics out there, so I see what you're saying.

I have to say that a lot of antibiotics seem pretty similar to me. No matter what kind I take, I always seem to end up with an upset stomach! It's very unpleasant, but I guess it's the price I pay for getting better.

Post 1

I am allergic to penicillin, so I can't take any drugs in that category. So it's lucky for me that there are drugs out there like metronidazole that aren't in the penicillin family and can treat bacterial infections.

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