Zidoval: Indications, Dosage, Precautions, Adverse Effects
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Zidoval – Product Information

Manufacture: iNova Pharmaceuticals
Country: Australia
Condition: Amebiasis, Aspiration Pneumonia, Aspiration Pneumonitis (Aspiration Pneumonia), Bacteremia, Bacterial Infection, Bacterial Vaginitis, Balantidium coli, Bone infection (Osteomyelitis), Crohn's Disease, Maintenance, Crohn's Disease, Acute, Clostridial Infection, Deep Neck Infection, Dental Abscess, Dracunculiasis, Diverticulitis, Dientamoeba fragilis, Endocarditis, Giardiasis, Helicobacter Pylori Infection, Intraabdominal Infection, Joint Infection, Lemierre's Syndrome, Meningitis, Nongonococcal Urethritis, Pelvic Inflammatory Disease, Peritonitis, Pneumonia, Pseudomembranous Colitis, Pouchitis, Skin or Soft Tissue Infection, Surgical Prophylaxis, STD Prophylaxis, Trichomoniasis, Vaginal Yeast Infection
Class: Amebicides, Miscellaneous antibiotics
Form: Cream, gel, liniment or balm, lotion, ointment, etc, Vaginal (e.g., douche, pessary, etc.)
Ingredients: metronidazole, carbomer 974P, propylene glycol, methyl hydroxy benzoate, propyl hydroxy benzoate, disodium edetate, sodium hydroxide, purified water

Vaginal Gel

(metronidazole 0.75%)

Name of the medicine

Name: Metronidazole.

Chemical Structure: Chemically, metronidazole is 2-methyl-5-nitroimidazole-1-ethanol. It has a chemical formula of C6H9N3O3, a molecular weight of 171.16, CAS No: 443-48-1; and has the following structure:


Zidoval Vaginal Gel is an intravaginal dosage form of the synthetic antibacterial agent, metronidazole, at a concentration of 0.75%. Metronidazole is a member of the imidazole class of antibacterial agents and is classified therapeutically as an anti-bacterial agent.

Zidoval Vaginal Gel is a non-sterile gelled, purified water solution, containing metronidazole at a concentration of 7.5 mg/g (0.75%). The gel is formulated at the normal vaginal pH of 4.0. The gel also contains carbomer 974P, disodium edetate, methylhydroxybenzoate, propylhydroxybenzoate, propylene glycol. Each 5 g applicator full of vaginal gel contains approximately 37.5 mg of metronidazole. Zidoval Vaginal Gel does not contain mineral oil.



Metronidazole is a synthetic agent which is effective against a wide range of obligate anaerobes. It is not effective against aerobes or facultative anaerobes. Against susceptible organisms, metronidazole is generally bactericidal at concentrations equal to or slightly higher than the minimum inhibitory concentration. The antibacterial activity results from the disruption of DNA and the inhibition of nucleic acid synthesis.

The aetiology of bacterial vaginosis is unclear and changes in vaginal flora which accompany bacterial vaginosis are probably its manifestation rather than its cause. Monitoring changes in vaginal flora by Gram stain slides of vaginal discharge smears may supplement diagnosis and assessment of treatment efficacy by standard clinical criteria.

Metronidazole has been shown to have in-vivo and clinical activity against:

  • Obligate anaerobic gram negative bacilli including Bacteroides species (B. fragilis, B. distasonis, B. ocatus, B. thetaiotaomicron, B. vulgaris) and Fusobacterium species.
  • Anaerobic gram positive bacilli including Clostridium species and susceptible strains of Eubacterium.
  • Anaerobic gram-positive cocci including Peptostreptococcus species.

Treatment success in bacterial vaginosis may be accompanied by a decrease in (but not elimination of) organism such as Gardnerella vaginalis and Bacterioides species. This may also be accompanied by an increase in Lactobacillus species in the vagina.


Healthy Volunteers: Following a single, intravaginal 5 g dose of Zidoval Vaginal Gel 0.75% (equivalent to 37.5 mg of metronidazole) administered to 12 healthy volunteers, a mean maximum serum metronidazole concentration of 237 ng/mL was achieved (range: 152 to 368 ng/mL). This is approximately 2% of the mean maximum serum metronidazole concentration achieved in the same subjects administered a single, oral 500 mg dose of metronidazole (mean Cmax = 12,785 ng/mL, range: 10,013 to 17,400 ng/mL). These peak concentrations were obtained between 6 to 12 hours after dosing with Zidoval Vaginal Gel and 1 to 3 hours after dosing with oral metronidazole. The extent of exposure (area under the curve [AUC]) of metronidazole, when administered as a single intravaginal 5g dose of Zidoval Vaginal Gel, was approximately 4% (4,977 ng/hr/mL) of the AUC of a single oral 500 mg dose of metronidazole (approximately 13,3395 ng/hr/mL). Dose-adjusted comparisons of AUCs indicated that the absorption of metronidazole administered vaginally was approximately half that of an equivalent oral dosage on a milligram-per-milligram comparison basis.

Patients With Bacterial Vaginosis: Following administration of 5 g doses of Zidoval Vaginal Gel twice daily for 5 days to 4 patients with bacterial vaginosis, mean maximum serum metronidazole concentrations of 214 ng/mL on day 1 and 294 ng/mL (range: 228 to 349 ng/mL) on day 5 (steady-state) were achieved. Steady-state metronidazole serum concentrations following oral dosages of 400 to 500 mg twice daily have been reported to range from 6,000 to 20,000 ng/mL.

Clinical trials

Four randomised, double-blind, controlled clinical studies demonstrated the effectiveness and safety of Zidoval Vaginal Gel in the treatment of bacterial vaginosis. The basis for clinical diagnosis of bacterial vaginosis in these studies were the presence of ≤20% clue cells in vaginal discharge and 2 of the following 3 clinical criteria: i) homogenous vaginal discharge; ii) a vaginal discharge with a pH?4.7; iii) a vaginal discharge emitting a positive amine odour test. In addition, Gram stains were also used to confirm accuracy of diagnosis in these studies. Patients were considered as treatment success if all 3 clinical criteria were absent and clue cells, if present, must be <20%.

In a randomised, double-blind, placebo-controlled clinical trial, Zidoval Vaginal Gel (5 g) given intravaginally twice daily for five days for treatment of bacterial vaginosis (assessed by Amsel Criteria) achieved treatment success (81%; n=43) at 12-16 days post-therapy that was statistically significantly greater than the placebo (11%; n=35). At follow-up visit (28-32 days post-therapy), treatment success for Zidoval Vaginal Gel (76%; n=38) was remained statistically significantly greater than the placebo (6%; n=34). Results of Gram stain scores agreed with clinical diagnosis overall in 90% cases at all visits combined.

In a randomised, investigator blinded, parallel clinical trial, Zidoval Vaginal Gel (5 g) given intravaginally twice daily for five days for treatment of bacterial vaginosis achieved comparable treatment successes (86%, n=37, at 2 weeks post initiation of therapy; 71%, n=34, at 4 weeks post initiation of therapy) to oral 500 mg metronidazole tablets given twice daily for 7 days (84%, n=44, at 2 weeks post initiation of therapy; 68%, n=41, at 4 weeks post initiation of therapy). Clinical and Gram stain diagnoses were in agreement 90% of the time.

In a randomised, double-blind clinical trial, Zidoval Vaginal Gel (5 g) given intravaginally twice daily for five days for treatment of bacterial vaginosis achieved comparable (p=0.333) treatment success (79%, n=103) at 12-16 days post-therapy to Sultrin (sulfathiazole, sulfacetamide, sulfabenzamide) cream given twice daily intravaginally for 5 days (71%,n=113). At follow-up visit (28-32 days post-therapy), treatment success for Zidoval Vaginal Gel (66%, n=96) was statistically significantly greater (p=0.018) than Sultrin (47%, n=109). Results of Gram stain scores agreed with clinical diagnosis overall in 89% cases in Zidoval group and in 87% in Sultrin group.

In a randomised, investigator blind clinical trial, the efficacy of Zidoval Vaginal Gel (5 g) given intravaginally twice daily versus once daily for five days for treatment of bacterial vaginosis was compared. At visit 2 (7-12 days post-therapy) and visit 3 (28-35 days post-therapy) respectively, 77% (n=199) and 58% (n=180) of patients were considered treatment success in the once daily dosing group. For the twice daily dosing regimen, corresponding treatment success rates were 80% (n=196) and 61% (n=178), respectively. Difference between treatment groups was not statistically significant. Gram stain scores and clinical diagnosis correlated in 83% cases.


Zidoval Vaginal Gel 0.75% is indicated in the treatment of symptomatic bacterial vaginosis (formerly referred to as Haemophilus vaginalis vaginitis, Gardnerella vaginalis vaginitis, non-specific vaginitis, Corynebacterium vaginale vaginitis or anaerobic vaginosis).

Note: For purposes of this indication, a clinical diagnosis of bacterial vaginosis is usually defined by the presence of at least three of the following four criteria:

  • a vaginal discharge pH of greater than 4.5;
  • a vaginal discharge emitting a “fishy” amine odor when mixed with a 10% KOH solution;
  • нa vaginal discharge containing clue cells on wet mount microscopy examination;
  • gram stain consistent with a diagnosis of bacterial vaginosis (Lactobacillus morphotype absent or markedly decreased, Gardnerella morphotype predominant flora, white blood cells absent or few, Mobiluncus morphotype may or may not be present).
  • A diagnosis of bacterial vaginosis requires that other pathogens which may be associated with genital infection, such as Trichomonas vaginalis, Candida albicans, Chlamydia trachomatis and Neisseria gonorrhoeae, should be ruled out by appropriate laboratory means.


    Zidoval Vaginal Gel is contraindicated for patients with a prior history of hypersensitivity to metronidazole, hydroxybenzoates, other ingredients of the formulation or other nitroimidazole derivatives.



    Approximately 6-10% of patients treated with Zidoval Vaginal Gel developed symptomatic Candida vaginitis during or immediately after therapy. This may be due to known or previously unrecognised vulvo vaginal candidiasis may present with more prominent symptoms during therapy. Zidoval Vaginal Gel contains ingredients that may cause burning and irritation of the eye. In the event of accidental contact with the eye, rinse the eye with copious amounts of cool tap water.

    Convulsive Seizures and Peripheral Neuropathy:

    Some patients treated with oral or intravenous metronidazole have been reported to have convulsive seizures or peripheral neuropathy, the latter characterised mainly by numbness or paraesthesia of an extremity. While the occurrence of serious neurological symptoms with Zidoval Vaginal Gel is unlikely, the appearance of abnormal neurological signs should prompt discontinuation of therapy. Zidoval Vaginal Gel should be administered with caution to patients with central nervous system diseases.

    Haematologic Effects:

    Some patients treated with oral metronidazole have been observed to have a mild transient leukopenia. Zidoval Vaginal Gel should be administered with caution to patients with evidence of or a history of blood dyscrasia.

    Carcinogenesis, Mutagenesis, Impairment of Fertility:

    Although metronidazole has shown mutagenic activity in several in vitro systems, including bacteria, there is no conclusive evidence of genotoxicity in mammals. Chronic oral administration of metronidazole showed increased tumour incidences in rats and mice. The results of rodent tests are not always indicative of human risk, in part, due to metabolic and digestive differences. While the results of genotoxicity, mutagenicity, and carcinogenicity assays of metronidazole in rodent-based systems and in vitro are equivocal, the human use of metronidazole as a therapeutic agent since 1960 shows no conclusive evidence of human genotoxicity, mutagenicity, and carcinogenicity at therapeutic levels of metronidazole. Retrospective studies in women treated systemically with metronidazole have revealed no increased incidence of tumor formation compared to the untreated population.

    Patients with Hepatic Impairment:

    Patients with severe hepatic disease metabolise metronidazole slowly. This may result in the accumulation of metronidazole and its metabolites in the plasma. Zidoval Vaginal Gel should be administered with caution in patients with evidence of hepatic dysfunction. However, a total treatment course of 187.5 mg is unlikely to lead to excessive serum levels.

    Patients with Renal Impairment:

    In patients with renal failure, there is no accumulation of metronidazole however hydroxy and acid metabolites are retained. Haemodialysis removes metronidazole and these metabolites.

    Use in Pregnancy (Category B2):

    The potential adverse effects of Zidoval Vaginal Gel on pregnancy have not been determined. Metronidazole crosses the placental barrier and enters the foetal circulation rapidly. Metronidazole blood levels are significantly lower after administration of Zidoval Vaginal Gel than those achieved with oral metronidazole.

    A substantial amount of data is available regarding the effects of human exposure to metronidazole in pregnancy over more than 30 years. A review on literature reports in 1469 women treated with metronidazole during pregnancy, 206 during the first trimester, concluded that the incidence of abortions, perinatal death and malformations, or of icterus neonatorum was not increased. A decade later, another literature review was published on 2139 women (254 treated with metronidazole during first trimester, 521 during second trimester, 554 during third trimester and 880 at an unspecified time during pregnancy0 concluded that metronidazole was safe during pregnancy.

    In 7 retrospective studies in UK and USA, the effect of metronidazole use was examined in 1776 pregnancies; in 246 pregnancies the drug was used during first trimester. Dosage regimens varied; oral dose of 250-750 mg/day for 7-10 days either alone or in combination with 500 mg vaginal suppository. No evidence of increase in the incidence of any particular abnormality was seen in these studies. Collectively, these studies led to the conclusion that metronidazole was safe to use during pregnancy, including during the first trimester.

    In two prescription-event studies, 2327 women who had a prescription for metronidazole filled at any time during pregnancy did not show an increase in the incidence of malformations in babies born to them.

    A meta-analysis of 7 studies (1336 patients exposed; 154163 patients with no exposure to the drug) showed no evidence of increased risk of malformation from the use of metronidazole during pregnancy. A similar analysis from 5 studies (2524 patients exposed and 196927 not exposed to drug) showed no relationship between metronidazole use during pregnancy and birth defects.

    In a prospective follow-up of 34 cases exposed to metronidazole during pregnancy, metronidazole was not considered to cause birth defects. Twenty five cases had received the drug during first trimester, seven during the second and one during the third trimester and date of exposure for one was not known.

    Although no conclusive evidence of fetotoxicity or teratogenicity has been observed in animal studies with other forms of metronidazole, and clinical experience to date with the use of metronidazole in pregnant women has revealed no evidence of a fetotoxic or teratogenic effect of the drug, there are no adequate and well-controlled studies of therapy with Zidoval Vaginal Gel in pregnant women.

    Intravenous and oral formulations of metronidazole are not recommended to be given in the first trimester of pregnancy because it crosses the placenta and enters the fetal circulation rapidly. Although it has not been shown to be teratogenic in either human or animal studies, such a possibility can not be excluded. Metronidazole vaginal gel should be used in pregnancy if no other treatment option is considered appropriate.

    Use in Lactation:

    After oral administration, metronidazole has been shown to be secreted in breast milk in concentrations similar to those found in plasma. Metronidazole plasma levels are significantly lower after administration of Zidoval Vaginal Gel than those achieved with oral metronidazole. Since the potential adverse effects of metronidazole on postnatal development have not been determined, thus a decision should be made, whether to discontinue breast-feeding or treatment with Zidoval Vaginal Gel, taking into account the importance of the treatment to the mother.

    Use in Children:

    The safety and efficacy of Zidoval Vaginal Gel in children have not been established.

    Interactions with othermedicines

    Zidoval Vaginal Gel therapy results in markedly lower serum levels of metronidazole when compared to oral metronidazole therapy. Although these lower serum levels are less likely to result in the interactions that have been observed with oral metronidazole, the possibility of these interactions can not be excluded.

    Alcohol: Concurrent usage of oral metronidazole and alcohol may result in a disulfiram-like reaction. Despite the relatively low serum levels of metronidazole produced following administration of Zidoval Vaginal Gel, the possibility of a disulfiram-like reaction to alcohol while on Zidoval therapy can not be excluded. Patients should be cautioned about drinking alcohol while being treated with Zidoval Vaginal Gel.

    Carmustine (BCNU) or cyclophosphamide: Metronidazole should be used with caution in patients receiving these drugs.

    Coumarin Anticoagulants: Oral metronidazole has been reported to potentiate the anticoagulant effect of warfarin and other coumarin anticoagulants, resulting in a prolongation of prothrombin time. Zidoval Vaginal Gel should be administered with caution in patients on this type of anticoagulant therapy.

    Cyclosporin and 5-Fluorouracil: Oral metronidazole has been shown to increase the plasma concentrations of cyclosporin and 5-fluorouracil. Although, vaginal administration of metronidazole results in markedly lower plasma metronidazole concentrations when compared to oral metronidazole, the possibility of these interactions can not be ruled out.

    Disulfiram: Concurrent usage of oral metronidazole and disulfiram have been reported to cause psychotic reactions in alcoholic patients. Zidoval Vaginal Gel should not be administered to patients who have taken disulfiram within the past 2 weeks.

    Lithium: Short-term oral metronidazole therapy in patients stabilised on relatively high doses of lithium has been associated with elevation of serum lithium levels and, in a few cases, signs of lithium toxicity.

    Effects on Drug/Laboratory Tests:

    Metronidazole may interfere with certain types of determinations of serum chemistry values, such as aspartate aminotransferase (AST, SGOT), alanine aminotransferase (ALT, SGPT), lactate dehydrogenase (LDH), triglycerides and glucose hexokinase. Values of zero may be observed. All of the assays in which interference has been reported involve enzymatic coupling of the assay to oxidation reduction of nicotinamide adenine dinucleotides (NAD+NADH). Interference is due to the similarity in absorbance peaks of NADH (340 nm) and metronidazole (322 nm) at pH 7.

    Dverse effects

    Clinical Trial Data

    In four randomised placebo- or active-controlled pivotal clinical trials, adverse events reported by the investigator as probably or possibly related to treatment and with an incidence of 1% or greater are presented in the table below. A dash represents an incidence of less than 1%.








    Oral Tablets




    Dosing regimen Od or bd

    5 days

    Bd for

    5 days

    500 mg bd for

    7 days

    Bd for

    5 days

    N=720 N=46 N=50 N=121
    Skin and Appendages
    Allergic Reaction - - 2.0% -
    Gastrointestinal Discomfort 4.7% - - -
    Nausea - - 18.0% 3.3%
    Nausea and Vomiting 2.2% - - -
    Unpleasant Taste/Feeling on Tongue 2.1% 2.2% 40.0% -
    Diarrhoea - - 10.0% 2.5%
    Decreased Appetite 1.1% - 6.0% -
    Constipation - - 12.0% -
    Abdominal Cramping - - 12.0% -
    Metallic Taste in Mouth - - - 1.7%
    Yeast Infection 8.6% - 22.0% 1.6%
    Vaginal Discharge 8.2% - 2.0% -
    Vulva/Vaginal Irritative Symptoms 6.1% - - -
    Itching, Vaginal and Perianal - 2.2% - -
    Vulvar Burning - 2.2% - -
    Vulvar Lesions - 2.2% - -
    Vaginal Itching - - 10.0% -
    Vaginal Burning - 2.2% - 2.5%
    Pelvic Discomfort 1.9% - - -
    Darkened Urine - - 20.0% -
    Dizziness 1.7% - 10.0% -
    Headache 2.1% - 4.0% -
    Fatigue - - 2.0% -
    Trouble Sleeping - - 6.0% -


    - - - 3.3%

    Post-Marketing Data

    The listing below includes all spontaneous adverse events, reported worldwide during the period of August 1992 to December 1997, and is presented at frequency of:

    Very Common≥1/10

    Common≥1/100 and&il;1/10

    Uncommon≥1/1000 and&il;1/100

    Rare≥1/10,000 and&il;1/1000

    Very Rare&il;1/10,000

    Application Site Disorder: Very rare: application site reaction

    Body as a Whole: Very rare: allergic reaction

    Central and Peripheral Nervous System Disorders: Very rare: dizziness, headache, paraesthesia

    Gastrointestinal System Disorders: Very rare: abdominal pain, diarrhoea, nausea

    Reproductive Disorders, Female: Very rare: leukorrhoea, vaginitis, vulvar disorder

    Skin and Appendages Disorder: Very rare: pruritus genital, rash, urticaria.

    Special Senses Other, Disorder: Very rare: taste perversion.

    Dosage and administration

    The recommended dose is one applicator full of Zidoval Vaginal Gel (approximately 5 g containing approximately 37.5 mg of metronidazole) intravaginally once a day, at bedtime, for 5 days.


    There is no human experience with overdosage of Zidoval Vaginal Gel. For information on the management of overdose, contact the Poison Information Centre on 131126 (Australia)

    Presentation and storage conditions

    Each 5 g of Zidoval Vaginal Gel 0.75% contains 37.5 mg of metronidazole. Zidoval Vaginal Gel is supplied in a 40 g tube and packaged with 5 disposable applicators.

    Store below 25oC. Do not freeze.