Secnidazole: Chemical Formula, Mechanism of Action, Indications, Precautions, Contraindications and Adverse Reactions

Secnidazole is a second-generation antimicrobial 5-nitroimidazole drug structurally related to other 5-nitroimidazoles, including Metronidazole and Tinidazole.

It is selective against many bacteria and protozoa Gram-positive and Gram-negative anaerobic.

In September 2017, the Food and Drug Administration approved secnidazole under the trade name Solosec as a single-dose oral treatment for bacterial vaginosis, a common vaginal infection in women aged 15 to 44 years.

Antimicrobial therapy only aims to treat or prevent infections proven or strongly suspected to be caused by susceptible bacteria.

Secnidazole shows selectivity against many Gram-positive and Gram-negative anaerobic bacteria and protozoa.

In vitro studies demonstrate the efficacy of the drug against Bacteroides fragilis, Trichomonas vaginalis, Gardnerella vaginalis, Entamoeba histolytica, and Giardia lamblia.

The secnidazole treatment reports no significant bacterial or protozoan resistance.


Chemical formula


1-(2-metil-5-nitroimidazol-1-il) propano-2-ol

Mechanism of action

Secnidazole enters the bacterial cell by diffusion as a prodrug without antimicrobial activity.

The drug becomes an active form when the bacterial enzymes reduce the nitro group to radical anions.

It is believed that radical anions interfere with the DNA synthesis of the bacterium by minimizing cell reproduction.


This drug is indicated for treating arthritis, vaginitis, amebiasis, or giardiasis affecting the liver and the digestive system.


The doctor will indicate the duration and dose of the most appropriate treatment for your particular case. The most common therapies with secnidazole, according to the pathology, are summarized in:

Intestinal amebiasis and giardiasis: For children> two years, a single dose of 30 mg per kilogram per day should be administered, with a maximum of 2000 mg. While for adults, a single dose of 2000 mg will be issued.

For asymptomatic amoebiasis, the minimum treatment should be prolonged for three days.

During the ingestion of Giardia lamblia, it is recommended to apply to all people living with the patient to avoid the reproduction of the disease.

Hepatic amoebiasis: Children> two years: 30 mg per kilogram per day with a maximum of 2000 mg in 5 – 7 days. Adults: 500 mg three times a day for 5 – 7 days.

Vaginal or urethral trichomoniasis: Adults: 2000 mg in a single dose.

If you miss a dose, take Secnidazole as soon as you remember it and then usually continue if necessary.

Doses should never be given twice to compensate for forgotten individual amounts.


The composition of the different presentations for this medicine may differ from one country to another.

This medication should not be used in the following cases:

• This medicine has lactose; contact your doctor before taking it if you have lactose intolerance.

• This medicine contains tartrazine (yellow dye), causing allergic reactions, mainly in patients with a history of reactions to aspirin. If you have allergies known as rhinitis, asthma, hives, and have allergic reactions to aspirin, check with your doctor before taking it.


The use of the drug is not recommended in the case of:

• Allergy (hypersensitivity) to the active substance secnidazole or other medicine components.

• If you have a severe liver disorder.

• If you have a blood dyscrasia.

• If you have an active organic disease of the nervous system.

• If you are being treated with lithium, anticoagulants, or phenobarbital. Ask your doctor before using.

• If you are taking or have recently taken any medication or are receiving treatment for kidney problems or any disease present such as antacids, sucralfate, even those without a prescription.

• Secnidazole enhances the effects of anticoagulants (warfarin, acenocoumarol), so abuse of this would increase the risk of bleeding.

• Simultaneous administration with phenobarbital decreases the effects of secnidazole and increases its elimination rate.

• Disulfiram and secnidazole (used in detoxifying alcohol) should not be administered simultaneously because they can cause neurological symptoms such as delirium and confusion.

• Simultaneous administration with cimetidine decreases its elimination and increases the risk of overdose.

• It should not be administered during pregnancy, especially during the first trimester.

Secnidazole reaches a concentration similar to maternal blood in breast milk, so it should not be given to nursing mothers.

A slight decrease in white blood cell count has been observed during treatment with secnidazole, so it is recommended to perform blood tests before and after treatment, especially if it is necessary to repeat the treatment in patients with amebiasis and trichomoniasis.

Adverse reactions

Occasionally, effects have been reported when secnidazole is administered, such as headache, heartburn, diarrhea or constipation, nausea, vomiting, vertigo, lack of appetite, dry mouth, and bad taste (metallic).

These effects are transient and do not require interruption of treatment.

The use of secnidazole can cause side effects such as:

• Decrease in white blood cells, particularly neutrophils and platelets (thrombocytopenia), both transient.

• Urticaria, rash and pruritus (itching).

• Convulsions, vertigo, motor incoordination with abnormal gait (ataxia), confusion, peripheral neuropathy, depression, irritability, sleep disturbance, and weakness.

• Cardiovascular side effects such as alterations in the ECG: QT prolongation.

• Genitourinary side effects: Cystitis, vaginal candidiasis, polyuria, urinary incontinence, dysuria, dark urine, dyspareunia, and decreased libido.

• Abdominal distention, proctitis, glossitis, hot flushes, fever, nasal congestion, and dry mucous membranes (oral, vaginal).

If these effects appear, you should immediately consult with the attending physician.