Nitazoxanide: can it treat Covid-19? Check the indication

Researchers and researchers are constantly looking for new drug treatments for various diseases. Often, drugs that are already commercialized for some conditions show potential for other diseases.

In early 2020, research on existing active substances was intensified due to the Coronavirus pandemic . Worldwide, treatments and vaccines for the infection are being tested in the laboratory and some are being tested in patients.

Among these drugs is Nitazoxanide, which is an active ingredient present in the Brazilian market for about 15 years, indicated as a broad spectrum antiparasitic and later for  viral gastroenteritis (rotavirus and norovirus). For the conditions listed on the package insert, the substance is an effective and safe treatment option.

Now, several clinical studies are being carried out in Brazil and in the world to evaluate the effects and benefits of the drug in patients with the new coronavirus . In order to encourage research, FQM Farmoquímica – a pharmaceutical industry that markets Annita ®, a reference drug based on Nitazoxanide – supported researchers and researchers in search of Covid-19 treatment.

See more about the substance and its relationship to Covid-19.


What is Nitazoxanide?

Nitazoxanide is the active substance, with broad spectrum antiparasitic action. That is, capable of combating different parasites, which are agents that invade the organism and can lead to pathologies, such as  giardiasis  (caused by giardia),  amoebiasis  (caused by amoeba) and others.

The substance is also approved for the treatment of viral gastroenteritis, caused by Rotavirus and Norovirus. Therefore, the drug is capable of combating different types of disease-causing agents.

According to the package insert, nitazoxanide fights  protozoa  by inhibiting an enzyme that is essential to the life of the agent. In relation to  worms , it is believed that the combat process is the same, although there may be other mechanisms involved. Already the  virus  suffer inhibition of the synthesis of their structures, which prevents them from multiplying.

The medication has reference (Anitta®) and generic options, being available in coated tablets or powder for suspension, both for oral use.

The administration of treatments to fight parasites is even indicated by the World Health Organization (WHO). According to the organization, about 880 million children worldwide need medication to fight microorganisms.

Thus, in regions with a high prevalence of soil-borne parasites (above 20%), WHO recommends that annual or semi-annual administration of antiparasitic drugs be carried out, according to the percentage of people affected.

Due to studies with this substance in the fight against Coronavirus, in April 2020, Nitazoxanide-based drugs started to require prescription retention, since it was included in the controlled medication ordinance (SVS / MS nº 344/1998). The change, guided by the National Health Surveillance Agency (ANVISA), was a safety measure to prevent self-medication and shortages of the drug on the market.

In June, the substance was added to the list of RDC No. 405/2020, ceasing to be a controlled drug, but still requiring prescription retention by the pharmacy.

However, the determination was suspended in early September, causing the substance to return for sale in a regular White prescription – that is, without prescription retention at the pharmacy or drugstore.

Nitazoxanide for the treatment of Covid-19

With the expansion of coronavirus cases worldwide, and the declaration of the pandemic by the WHO, several researches were mobilized to find treatments and vaccines. Currently, several substances are being tested, as they have the potential to prevent, treat the disease and / or reduce mortality.

Among these drugs is Nitazoxanide. One of the first studies started in Wuhan, China, considered it as a potential inhibitor of SarsCOV-2.

The drug has been studied for other indications in addition to those described in the package insert for a while. There are researches that prove the effectiveness of the drug in vitro for the treatment of some viral diseases, including those that affect the respiratory system.

Among scientific publications, in vitro tests   (H1N1, Ebola and SARS-Cov1) and  in vivo  (H1N1), the substance shows promising results in antiviral action. SARS-Cov2, which is the new coronavirus, has a similar structure to SARS-Cov1 and shares some mechanisms of cell infection, such as receptors for entry into the cell. Therefore, it is believed that there can be good results.

It is worth mentioning that in vitro  and  in vivo tests  , even if they present quite high efficacy results, still do not indicate that the drug is effective and safe for the treatment of humans.

In vitro tests   are carried out in the laboratory, in which the substance is injected into isolated cells, which are very preliminary studies. In vivo tests   are performed on animals and / or humans (depending on the phase of the study), representing an important step in the efficacy and safety of the drug, since only in this way is it possible to consider the various biological interactions in the administration of the drug.

This search occurs, in addition to the potential for new indications, due to the fact that the drug has a good safety profile in different doses and treatment regimens, and can be used by adults, the elderly and children.

According to research, the substance has no relevant toxicity and, therefore, the risks for people with different diseases are low, but should always be considered by the prescribing physician.

The side effect, presented in patients who used Nitazoxanide in treatments, is the yellow-green color in secretions, mainly urine.

Although in vitro studies report effectiveness in inhibiting the virus, the researchers cannot say that there will be the same results in the in vivo tests . Therefore, it is important to highlight that there is still no scientific evidence on the effectiveness of using the substance in cases of coronavirus.

Do you need a prescription?

Medicines based on the active ingredient Nitazoxanide should be prescribed by a doctor, but they no longer need to have their prescription withheld at pharmacies and drugstores.

Due to studies on the potential action to combat the new coronavirus, in April 2020, Anvisa had determined the special sale control of this substance (SVS / MS nº 344/1998). As a result, it became necessary to retain a prescription by the pharmacy or drugstore.

The measure aimed to ensure that there was no indiscriminate use, as well as the scarcity of the substance on the market, affecting the treatment of patients who were already using it.

In the month of June, Nitazoxanida started to be delimited by the Collegiate Board Resolution (RDC) nº405 / 2020. The substances listed in this resolution are not of special control, but a two-way prescription is required, with retention in the pharmacy or drugstore.

However, at the beginning of September, Anvisa’s framework was suspended, so that Nitazoxanide was once again sold with a common White prescription, without being retained at the pharmacy.

Why is it so difficult to enter a drug to fight the new coronavirus?

The reason why it is so complex to find substances capable of fighting viruses is basically the fact that they have no cellular structure – unlike other microorganisms, such as bacteria, for example. This means that viruses need to invade cells to ensure survival and multiply.

It is this structure that facilitates drug discovery, as the drug acts on the cell wall, destroying the microorganism.

However, as viruses are infiltrated into the human cell, destroying it usually causes the human cell to be affected as well. That is, the drug becomes toxic to the body.

Therefore, there needs to be a separation between the infectious agent and the human cell. Only then is the medicine safe to use.

This process is long and usually takes a long time. So, one way to speed up research, while maintaining all care, is to identify drugs already on the market, but approved for other conditions. That is, the studies start from observations and laboratory tests on drugs already used by the population.

What is the medicine for?

According to the package insert, the active substance Nitazoxanide is indicated for the treatment of the following conditions:

Viral gastroenteritis

Viral gastroenteritis are infections caused by viruses that affect the intestinal tract (stomach or intestine). When they are caused by viruses of the rotavirus and norovirus groups, Nitazoxanide can be indicated to fight the agent.

In general, viral gastroenteritis causes fever , abdominal pain, nausea, vomiting and diarrhea . On average, this condition is a major cause of diarrhea due to infectious conditions.


Helminthiasis are diseases caused by intestinal helminths. They are pathological agents that can be acquired through contact with contaminated feces or unhygienic food.

The prevalence of infection is high, especially in regions without basic sanitation. Among the conditions that can be treated with Nitazoxanide are those caused by:

  • Nematodes;
  • Cestodes;
  • Trematodes, such as Enterobius vermicularis , Ascaris lumbricoides , Strongyloides stercolaris , Ancylostoma duodenale , Necator americanus , Trichuris trichiura , Taenia sp and Hymenolepis nana .


Amoebas can be transmitted from person to person, through contaminated water or food. In general, amoebiasis causes diarrhea, abdominal cramps, nausea and tenderness.

The drug Nitazoxanide can be prescribed for the treatment of diarrhea due to acute intestinal amebiasis or amoebic dysentery caused by the entamoeba histolytica / disparate complex .


The giardiasis is caused by the protozoan Giardia lamblia , which affects the small intestine. The main routes of contamination are through ingestion of contaminated water or food. In addition, poor hygiene or sexual contact with an infected person can also transmit giardiasis.

For the treatment of diarrhea caused by Giardia lamblia or Giardia intestinalis , Nitazoxanide can be prescribed.


Cryptosporidium infections are called Cryptosporidiosis. The condition is very common in children, and its transmission occurs through the ingestion of food or water contaminated by feces. Direct contact and zoonotic spread are also sources of contamination.

Nitazoxanide can be indicated for the treatment of diarrhea caused by Cryptosporidium parvum.

Other intestinal infections

Other intestinal infections can be treated with the drug Nitazoxanide. In general, the main symptoms triggered are diarrhea and abdominal pain. Are they:

  • Blastocystosis: caused by the parasite Blastocistis hominis .
  • Balantidiasis: caused by the parasite Balantidium coli ;
  • Isosporiasis: caused by the parasite Isospora belli .

How does the medicine work in the body?

On average, Nitazoxanide starts to act between 2 and 4 hours after ingestion. According to the package insert, in relation to worms, Nitazoxanide acts by inhibiting an enzyme that is essential for the parasite’s energy metabolism. This enzyme is pyruvate ferredoxin oxidoreductase, which is indispensable for the survival of some microorganisms.

For protozoa, the inhibition mechanism is believed to be the same, although there may be others involved and not yet fully known. As for fighting viruses, the drug acts by inhibiting the synthesis of the viral structure, which makes the microorganism unable to multiply.

Dosage and how to take

The package insert indicates that Nitazoxanide should preferably be taken with food, as this guarantees a high absorption of it.

Guidance in relation to dosage, time of treatment, as well as schedules and other care must be guided by the doctor in charge. As a protocol, the condition (which infection), age and weight of the patient should be considered.

In general, treatment is usually done for 3 consecutive days, according to medical advice. However, if there is any associated condition or disease, such as immunosuppression, the time can be changed. In all cases, it is essential to follow medical guidelines .

It is also worth mentioning that, although the medication is being tested for the coronavirus, it should not be taken without a medical prescription in cases of suspected or confirmed Covid-19, even as a means of prevention.

What are the side effects?

As with any medication, the use of Nitazoxanide can trigger adverse reactions. According to the package insert, the frames considered common are:

  • Colic-type abdominal pain;
  • Diarrhea;
  • Nausea;
  • Vomiting;
  • Headache (headache).

The package insert also highlights that treatment with medication can produce changes in the color of physiological fluids. Thus, it may happen that patients notice that the urine or sperm, for example, have a greenish yellow color.

However, this has no clinical significance, being due to the coloring of some components of the formula.

Other reactions may also occur, but are considered unusual. If any symptomatic manifestations are noticed, it is essential to seek medical advice.

Price and where to buy

Reference drugs ( Anitta ) or generic Nitazoxanide- based drugs can be purchased at physical pharmacies or researched at online price comparators, such as Consulta Remédios.