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Mix of Flagyl and Marijuana

Many people use cannabis to feel better both mentally (relieve anxiety, relax, boost mood) and physically (alleviate chronic pain). It is logical that those who use weed might want to try and combine it with antibacterial therapy while treating an infection. But is it really a good idea to mix metronidazole and marijuana?

What is Flagyl

Flagyl is one of the brand names for metronidazole—an antibacterial and antiprotozoal drug of the nitroimidazole class. It can be administered through the mouth (orally), on the skin (topically), or through an IV injection (parenterally). It can be obtained as a generic or under other brand names, such as Metrogyl, Anabact, Efloran, etc.

Common Uses

Metronidazole is indicated for the treatment of parasitic invasions, such as amebiasis and trichomoniasis, and susceptible bacterial infections that affect:

  • repruductive system (bacterial vaginosis, endometritis, etc.);
  • heart (endocarditis—inflammation in the endocardium, lining inside heart valves and chambers);
  • blood (bacterial septicemia);
  • gastrointestinal tract (peritonitis, intra-abdominal and liver abscess);
  • brain (meningitis, cerebral abscess);
  • lower respiratory tract (pneumonia, lung abscess);
  • skin and its structures (dermatitis, rosacea);
  • locomotor system (bones and joints infections).

If a person has been diagnosed with an STI and their partner does not have symptoms, they may be prescribed Flagyl.

How it Works

Metronidazole diffuses into a bacteria cell through its membrane and promotes the formation of cytotoxic free radicals. The cytotoxic particles then interact with the DNA of the host cells, causing strand breakage and loss of helical DNA structure. This causes cell death.

Side Effects

  • paresthesia in the limbs (burning or tingling sensation);
  • numbness in the limbs;
  • flushing;
  • weakness;
  • nasal congestion;
  • headaches;
  • vertigo;
  • dizziness;
  • confusion;
  • insomnia;
  • syncope;
  • nausea;
  • abdominal cramps;
  • vomiting;
  • diarrhea;
  • constipation;
  • dry mouth, bad metallic taste on the tongue;
  • rash;
  • dysuria (pain or burning sensation during urination);
  • cystitis;
  • yeast infection.

The list of side effects does not mean you would get all of them—it includes adverse reactions that were reported by all the patients who used the drug. However, if you notice any malaise that you suspect may be caused by metronidazole, contact your doctor right away.

What is Marijuana

Marijuana, or weed, is a substance made from dried and crushed flowers, leaves, seeds, and stems of the plants Cannabis sativa and Cannabis indica. It contains more than 400 bioactive compounds, including terpenoids and flavonoids. The main constituents responsible for the net effect of weed are cannabinoids: THC and CBD.


THC, or tetrahydrocannabinol, is a cannabinoid that makes a marijuana user “high”. It actively binds to the CB1 and CB2 cannabinoid receptors. The CB1 receptor is located in the CNS and triggers the release of norepinephrine, dopamine, serotonin, and gamma-aminobutyric acid(GABA). The CB2 receptor affects inflammatory and immune processes.


CBD, or cannabidiol, is a less addictive cannabinoid that does not create a sense of being high. It is also less active than THC and requires its presence to bind to the CB1 and CB2 receptors, moderating the activity of THC in turn. The significant feature of CBD is that it affects endocannabinoids—cannabinoid neurotransmitters that are naturally produced in the body. CBD enhances their effect on the body and inhibits their decomposition.

Can I Smoke Weed While Taking Flagyl?

Interactions between Flagyl and cannabis have not been extensively researched, and the available data is lacking. We do know that both are metabolized by the liver, so simultaneous administration may increase the load on the organ. Without being metabolized as effectively, there will be a higher concentration of drugs in the blood, which increases the risk of side effects and enhances them.

Additionally, some people use vape weed instead of smoking it. Vaping liquids often contain propylene glycol—a compound with two alcohol groups and the same metabolic path as alcohol. Just like alcohol does, in combination with metronidazole, it triggers a disulfiram-like reaction: intoxication with intermediate products of its decomposition.

Risks and Side Effects

There is a suggestion that taking antibiotics and weed together is beneficial. For instance, marijuana has antibacterial properties which may help overcome antibacterial resistance and intensify the effect of AB medication. Plus, weed can reduce pain and inflammation—a desirable effect for those who struggle with an infection.

However, there is not enough proof to support this theory, and the supposed benefits do not outweigh the proven risks the patient is exposed to when they combine metronidazole and weed.

Potential Side Effects

Adverse effects of marijuana include:

  • increased heart rate;
  • dry mouth;
  • altered perception (of time, colors, etc.);
  • impaired coordination;
  • brain fog;
  • agitation;
  • mood swings;
  • anxiety;
  • panic attack.

If you compare the lists of side effects, especially those on the CNS and movement, you can see an overlap in adverse reactions to metronidazole and THC (because it is mainly THC that affects the brain). This means that the combination increases the risk of a certain side effect developing or intensifying.

Flagyl Treatment Effectiveness

Aside from being metabolized by the liver itself, weed also alters the synthesis of certain enzymes in the liver. This changes the metabolic pathways for antibiotics taken with weed: they are processed more slowly, their efficacy is impeded, and treatment becomes longer and more difficult, with a higher risk of complications.

Take Flagyl Safely

To avoid unwanted drug interactions and side effects, always follow the recommendations given by your doctor or pharmacist and refrain from smoking weed, consuming alcohol, and vaping, till three days after the end of the treatment course. Here is why you should do this.

No Marijuana

As follows from this material, smoking weed can:

  1. increase the risk of side effects and make them stronger;
  2. decrease the efficacy of the medication and prolong treatment.

No Alcohol

You already know about the disulfiram-like reactions. Taking metronidazole and products that contain alcohol (including cough syrups, etc.) together may cause intoxication that results in:

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

No Vaping

Not only you should not vape weed while on Flagyl, better avoid vaping at all. Again, this is because of a disulfiram-like reaction with propylene glycol in vaping liquids.


While simultaneous use of Flagyl and weed provides theoretical benefits, there are many more risks. Weed can make the treatment less efficient and amplify potential side effects. Therefore, it is best to stop using weed until your treatment is finished.


What to avoid while taking Flagyl?

You should not use weed, alcohol, vapes, and tobacco cigarettes.

What medicine should you not take with marijuana?

Antibiotics are the first that comes to mind. You should not also combine marijuana with antidepressants and other drugs changing your mental state. For other drugs, ask your doctor about possible interactions.

Can you take CBD with metronidazole?

Best to avoid this combination: CBD can decrease the efficacy of the medication.

Why can’t you eat bananas with metronidazole?

Bananas are high in potassium, and metronidazole can change its levels in the body. Therefore, there could be an unfortunate imbalance in potassium levels with dangerous side effects.