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Fasigyn Side Effects

Generic name: tinidazole

Medically reviewed by Last updated on Mar 27, 2021.

Note: This document contains side effect information about tinidazole. Some of the dosage forms listed on this page may not apply to the brand name Fasigyn.

For the Consumer

Applies to tinidazole: oral tablet


Oral route (Tablet)

Carcinogenicity has been seen in mice and rats treated chronically with metronidazole, another nitroimidazole agent. Although such data have not been reported for tinidazole, the two drugs are structurally related and have similar biologic effects. Limit use of tinidazole to approved indication only. Avoid chronic use.

Side effects requiring immediate medical attention

Along with its needed effects, tinidazole (the active ingredient contained in Fasigyn) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking tinidazole:


  • Change in consciousness
  • cough
  • loss of consciousness
  • tightness in chest
  • troubled breathing

Incidence not known

  • Black, tarry stools
  • bleeding gums
  • blood in urine or stools
  • burning, numbness, tingling, or painful sensations
  • chest pain
  • chills
  • difficulty swallowing
  • fast, irregular, pounding, or racing heartbeat or pulse
  • fever
  • hives, itching, rash
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • lower back or side pain
  • nausea
  • painful or difficult urination
  • pale skin
  • pinpoint red spots on the skin
  • reddening of the skin, especially around ears
  • seizures
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swelling of eyes, face, or inside of the nose
  • swollen glands
  • ulcers
  • unsteadiness or awkwardness
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • weakness in the arms, hands, legs, or feet

Side effects not requiring immediate medical attention

Some side effects of tinidazole may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Bitter taste
  • metallic taste

Less common


  • Body aches or pain
  • coating on tongue
  • depression
  • hoarseness
  • mood or mental changes
  • runny nose
  • tender, swollen glands in the neck
  • voice changes

Incidence not known

  • Darkened urine
  • diarrhea
  • difficulty in moving
  • feeling of constant movement of self or surroundings
  • giddiness
  • lightheadedness
  • muscle pain or stiffness
  • pain, swelling, or redness in joints
  • sensation of spinning
  • shakiness and unsteady walk
  • sleepiness
  • swelling of the mouth
  • tongue discoloration
  • trembling, or other problems with muscle control or coordination
  • trouble sleeping
  • unable to sleep
  • white or brownish vaginal discharge
  • white patches in the mouth or throat or on the tongue

For Healthcare Professionals

Applies to tinidazole: compounding powder, oral tablet


Reported side effects were typically mild, infrequent, and self-limiting. Gastrointestinal side effects were reported most often.[Ref]


Common (1% to 10%): Nausea, dyspepsia/cramps/epigastric discomfort, vomiting, constipation, diarrhea, abdominal pain, flatulence

Rare (0.01% to 0.1%): Furry tongue

Frequency not reported: Tongue discoloration, stomatitis, dryness of mouth, salivation, oral candidiasis, glossitis[Ref]

Nervous system

Common (1% to 10%): Metallic/bitter taste, headache, dizziness, vertigo

Rare (0.01% to 0.1%): Coma

Frequency not reported: Convulsions, peripheral neuropathy, ataxia, giddiness, drowsiness, burning sensation, paresthesia, hypoesthesia/numbness, sensory disturbances, dysgeusia, taste change[Ref]


Common (1% to 10%): Weakness/fatigue/malaise

Frequency not reported: Flushing, fever/pyrexia, thirst, Candida overgrowth, fatigue, malaise[Ref]


Common (1% to 10%): Allergic dermatitis, pruritus

Frequency not reported: Urticaria, rash, sweating, angioedema, fixed drug eruption[Ref]

In a study involving 450 patients with fixed drug eruptions, 8 patients were found to have this oral drug as the probable causative agent. The fixed drug eruptions varied as to duration, shape and size, symptoms, number of lesions, and body site(s) affected. The study did not break these factors down for each individual causative agent.[Ref]


Common (1% to 10%): Anorexia, decreased appetite


Common (1% to 10%): Urinary tract infection, dysuria/painful urination, urine abnormality, pelvic pain, vulvovaginal discomfort, vaginal odor, menorrhagia

Frequency not reported: Darkened urine/chromaturia, increased vaginal discharge, female genital pruritus, Candida vaginitis[Ref]


Common (1% to 10%): Upper respiratory tract infection

Rare (0.01% to 0.1%): Bronchospasm, dyspnea, pharyngitis[Ref]


Rare (0.01% to 0.1%): Confusion, depression

Frequency not reported: Insomnia[Ref]


Rare (0.01% to 0.1%): Reversible thrombocytopenia

Frequency not reported: Neutropenia, leukopenia, increased eosinophil count, decreased hemoglobin[Ref]


Severe acute hypersensitivity reactions have been reported during initial or subsequent exposure to this drug.[Ref]

Frequency not reported: Drug hypersensitivity

Postmarketing reports: Severe acute hypersensitivity reactions, hypersensitivity reactions (included urticaria, pruritus, rash, flushing, sweating, dryness of mouth, fever, burning sensation, thirst, salivation, angioedema, Stevens-Johnson syndrome, erythema multiforme)[Ref]


Frequency not reported: Hepatic abnormalities (included raised transaminase level), increased AST, increased blood bilirubin[Ref]


Frequency not reported: Increased blood urea[Ref]


Frequency not reported: Palpitations[Ref]


Frequency not reported: Arthralgias, myalgias, arthritis[Ref]

More about Fasigyn (tinidazole)

Consumer resources

Other brands

Professional resources

Related treatment guides


1. Cerner Multum, Inc. "Australian Product Information." O 0

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. "Product Information. Tindamax (tinidazole)." Presutti Laboratories Inc, Arlington Heights, IL.

4. Mahboob A, Haroon TS "Drugs causing fixed eruptions: a study of 450 cases." Int J Dermatol 37 (1998): 833-8

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.