Metronidazole and vaping

Metronidazole and Vaping

By Nicholas White

In 2021, the CDC reported that 4,5% of adults were active users of electronic cigarettes. In 2022, a survey among middle and high school users showed that 3.3% and 14,1% of them, respectively, currently used e-cigarettes. The percentage may seem minor but it means millions of people. Metronidazole is a common prescription for the treatment of bacterial infections and parasitic invasions.

These two facts lead to a logical conclusion that a person who is prescribed metronidazole may vape more or less often. But is it safe? Can one still enjoy vaping while taking Flagyl or its analog, is it better to wait, and why? We are discussing the matter in this article.

What is Metronidazole

Let us start with the basics. Metronidazole is an antibacterial drug of the nitroimidazole group. Its main indications are bacterial and protozoal infections. The drug will not be effective against viruses, including COVID-19, or common flu. There are oral, topical, and parenteral forms of this medication.

Metronidazole can be obtained under various brand names:

  • Anabact;
  • Flagyl;
  • Metrogyl;
  • Metrosa;
  • Zidival;
  • Efloran, etc.

Main uses

  • Asymptomatic and symptomatic trichomoniasis;
  • AB therapy for sexual partners if they demonstrate no STI symptoms;
  • Amebiasis;
  • Serious anaerobic infections caused by bacteria prone to the medication.

The latter includes infections that affect:

  • Blood (bacterial septicemia);
  • Heart (e.g. endocarditis—inflammation in the heart’s inner lining);
  • Reproductive system in AFAB patients: tubo-ovarian abscess, endomyometritis, endometritis, bacterial vaginosis, etc.
  • GI tract: abscess of the liver, peritonitis, intra-abdominal abscess.
  • CNS: brain abscess, meningitis, etc.
  • Lower respiratory tract: lung abscess, empyema, pneumonia.
  • Skin: rosacea, dermatitis, etc.
  • Bones and joints.

How Flagyl Works

Metronidazole creates cytotoxic free radicals that cause DNA strand breakage in the targeted cell and fatally destabilize the DNA helix. The process results in the cell death.

Flagyl Side Effects

During the treatment with metronidazole, patients reported the following adverse reactions:

  • peripheral neuropathy after prolonged therapy, manifested by numbness or paresthesia in the limbs;
  • vertigo;
  • syncope;
  • confusion;
  • dizziness;
  • weakness;
  • insomnia;
  • headaches;
  • abdominal cramps;
  • nausea;
  • constipation;
  • vomiting;
  • diarrhea;
  • mouth dryness;
  • bad taste in the mouth;
  • rash;
  • flushing;
  • nasal congestion;
  • fever;
  • dysuria (pain or burning sensation during urination);
  • cystitis;
  • Candida overgrowth (yeast infection).

Metronidazole can also invoke reversible changes in blood: leukopenia and thrombocytopenia.

If the patient feels unwell and suspects their treatment may be the reason, they should contact their doctor as soon as possible.

How Vaping Works and Its Effects on the Body

A vape, or electronic cigarette, is a device that creates an inhalable aerosol by heating flavored liquid (often, nicotine-containing). While vaping is less aggressive than smoking, it still has a significant negative impact on health. Nicotine is an addictive substance, and liquids also contain cancer-causing agents, heavy metals, and volatile organic compounds. When a vaper inhales aerosol from the device, harmful chemicals get deep into the lungs. Studies also say that vaping promotes the development of cardiovascular conditions.

Potential Risks

The issue with metronidazole and vaping is caused by something called a disulfiram-like reaction. An active compound called disulfiram irreversibly inhibits aldehyde dehydrogenase—the enzyme that is necessary to process acetaldehyde. The latter is a toxic compound, an in-between product of alcohol metabolism. When disulfiram is taken with alcohol, a fast and severe intoxication occurs. Metronidazole has a similar effect.

Ingesting together alcohol-containing products and metronidazole can lead to a lot of unpleasant and even dangerous symptoms:

  • Dizziness and weakness.
  • Nausea and vomiting;
  • Breathlessness, hyperventilation;
  • Throbbing pain in the head and neck;
  • Pain in the chest and heart palpitations;
  • Loss of consciousness;
  • Arrhythmia;
  • Seizure and convulsions;
  • Acute congestive heart failure;
  • Cardiovascular collapse;
  • Myocardial infarction;
  • Respiratory depression.

This is why doctors always stress that patients should not consume anything that contains alcohol while on metronidazole, even cough syrup.

The connection between disulfiram-like reaction and vaping lies in propylene glycol, a main ingredient in the majority of e-liquids. Propylene glycol is a diol which means its molecule has two alcohol groups (to compare, ethanol contains one). In the body, it is metabolized by the same enzyme, aldehyde dehydrogenase. With this enzyme inhibited during metronidazole treatment, toxic products of partial metabolism will accumulate and intoxicate the body.

Can I Vape While Taking Metronidazole?

Clinical evidence on disulfiram-like reactions with metronidazole and propylene glycol is inconsistent, and there never were good clinical trials with a large pool of volunteers. However, labels on Flagyl and other metronidazole drugs advise you to avoid products that contain propylene glycol for at least three days after your treatment is finished. To avoid health risks, it is better to allow the medication to do its job and fully leave your system.

Customer Reviews

The topic is mostly discussed on vaping forums where people share their experiences with electronic cigarettes. Those who vaped while on metronidazole, tell different stories:

“I took a risk and vaped for 2 days on the drug and then out of nowhere had severe side effects and almost had to call 911 on myself. Never have been so scared in my life.”

“Did not know about the issue and vaped a lot. My 7-day treatment went fine.”

“Reduced how much I vape and use nicotine lozenges for the urge. However, my heart pounded with the last puff.”


Metronidazole can cause a dangerous interaction with propylene glycol, a compound often found in liquids for vaping. While some people may feel fine, others can experience mild to severe side effects. It is recommended to pause vaping until 3 days after the end of metronidazole treatment.


Can I smoke nicotine while taking metronidazole?

It is not recommended. Nicotine reduces drug concentration in blood plasma and can intensify its side effects.

Does vaping interfere with antibiotics?

Compounds in vaping liquids may interact with some antibiotics. It is also found that e-cigarettes may promote antibiotic resistance.

What to avoid with metronidazole?

Smoking, vaping, and alcohol consumption are to be avoided.

Should you avoid propylene glycol while taking metronidazole?

Yes, it is recommended to wait up to three days after the end of treatment.