Metropast

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Metropast

Quick Facts

Property Description
Active ingredient Metronidazole
Form Topical Paste
Pharmacological class Nitroimidazole Derivative, Antimicrobial Agent
General Target Anaerobic Bacteria and Protozoa
Origin Synthetic Compound

What Type of Medicine is Metropast and Its Core Component?

Metropast is a prescription-only pharmaceutical preparation whose therapeutic activity is centered on the active ingredient Metronidazole, a synthetic compound. This medication belongs to the Nitroimidazole Derivative pharmacological class, classifying it as a specialized Antimicrobial Agent.

The compound's efficacy against obligate anaerobic bacteria is widely recognized, distinguishing its role among anti-infective agents. The drug is designed to kill the types of germs that thrive in environments lacking oxygen, a characteristic consistent with its mechanism of action against susceptible microbial life forms.

Specialized Composition: Paste Formulation and Targeted Delivery

Metropast is defined by its unique presentation as a specialized paste, which is a type of topical preparation intended solely for local application. This formulation is a key differentiator, as it dictates the method of delivery and therapeutic profile of the compound.

Unlike oral tablets or systemic Metronidazole forms, the paste is specifically manufactured to provide a high-concentration reservoir directly at the point of application. This localized approach ensures that the active ingredient is released continuously over a sustained period exactly where it is needed, minimizing drug distribution throughout the body and maximizing the therapeutic effect at the target site.

General Purpose: Elimination of Anaerobic Pathogens

The general purpose of Metropast is to actively control and eliminate microorganisms that thrive in environments lacking sufficient oxygen, namely anaerobic bacteria and certain protozoa. This type of medication is typically used to manage local infections driven by oxygen-sensitive germs, functioning as a targeted therapeutic tool to reduce the microbial burden associated with localized conditions.

Metronidazole achieves this by utilizing a unique mechanism where it becomes chemically activated inside the target pathogen, leading to the destruction of the microbe's fundamental genetic material. By effectively neutralizing these specific infectious agents, the preparation’s function is to support the resolution of pathogen-driven processes locally.

Regulatory References

  1. MedlinePlus Drug Information

What side effects are possible with Metropast?

Possible Side Effects and Safety Information

The safety profile of Metropast, a metronidazole topical paste, is largely defined by localized reactions, reflecting the medication’s application site. Regulatory classification of adverse reactions primarily focuses on Skin and Subcutaneous Tissue Disorders.


Frequency-Classified Adverse Reactions

The most frequently reported adverse effects in clinical studies are local reactions, often classified as Common (affecting 1 in 100 users). Other reactions are documented but occur less frequently.

Classification Examples of Officially Documented Effects
Common Application site irritation, burning or stinging, erythema (redness), skin dryness, pruritus (itching).
Uncommon/Rare Nausea, metallic taste, headache, transient numbness or tingling.

Serious Safety Considerations

The official labeling notes that although systemic absorption is low with the paste, the drug substance, metronidazole, is associated with certain serious risks. These include the potential for Peripheral Neuropathy (numbness or paresthesia) and a warning regarding its use in patients with a history of blood dyscrasias.


Population-Specific Constraints

Specific regulatory statements exist for certain patient groups: safety and effectiveness have not been established in pediatric patients. Use during pregnancy or by nursing mothers requires careful assessment, as metronidazole is known to be secreted into breast milk after oral use, despite low systemic levels from topical application.


Safety Restrictions and Patterns

The label mandates that the paste must avoid contact with the eyes and mucous membranes to prevent severe local irritation. Local cutaneous effects such as stinging are often reported to be more prominent at the start of treatment, while the risk of serious systemic effects is mainly associated with the potential for cumulative or long-term exposure to the drug substance.

Overdose and Emergency Response

Overdose Manifestations and Systemic Risk

Metropast is a topical product, yet official regulatory documentation acknowledges that its active ingredient, Metronidazole, can be absorbed in sufficient amount to produce systemic effects. While there are no reported human experiences of overdosage specifically with the topical paste formulation, the official overdose profile addresses the risk of metronidazole toxicity. Overdose manifestations officially documented in high-exposure cases include Nausea, Vomiting, Ataxia (lack of voluntary coordination), and Mild disorientation. More severe neurological outcomes that have been reported include Convulsive seizures, Encephalopathy, and Peripheral neuropathy.


Emergency Action and Management

The official regulatory response to overdose requires symptomatic and supportive therapy, as authorities state that no specific antidote is known. The appearance of abnormal neurological signs mandates prompt evaluation and potential discontinuation of therapy. Immediate medical attention is required for severe manifestations, consistent with the official procedure for managing potential systemic toxicity.


Population-Specific Overdose Considerations

A specific consideration exists for patients with Cockayne Syndrome, who have a documented risk of severe hepatotoxicity and acute hepatic failure. For this high-risk group, frequent liver function tests are required, and the medication must be immediately discontinued if symptoms of liver injury (such as jaundice or abdominal pain) occur.

Therapeutic Uses of Metropast

What Metropast Treats: Main Uses and Benefits

This type of medication is commonly used to help manage symptoms related to specific inflammatory and infectious states. The paste is used in contexts where symptoms are related to inflammatory or irritative states and additional management of discomfort is needed.

Metropast is relevant in clinical settings for three main categories of conditions: managing inflammatory skin manifestations such as the papules and pustules of rosacea; treating anaerobic infections in tissue pockets (e.g., as supportive therapy in periodontitis); and controlling the microbial burden in chronic skin ulcers. The therapeutic benefit involves providing targeted support to address symptom clusters and contributes to easing the overall symptom load.

“The paste formulation may help manage localized symptoms that interfere with daily comfort, particularly those driven by specific microbial and inflammatory processes.”

This medication assists with managing symptoms related to inflammatory states and supports patients during episodes of heightened discomfort.


Quick Fact: Relief for Inflammatory Symptoms Metropast is commonly used to address groups of symptoms that may become intense, including facial redness, the formation of inflammatory bumps, and the foul odor often associated with symptoms that create noticeable physiological strain.

Eligibility and Restrictions for Use

Population Eligibility and Restrictions

The eligibility for Metropast (Topical Metronidazole) is strictly defined by official regulatory documents, establishing clear limitations on who can and cannot use the medicine.

Absolute Prohibition (Contraindications)

Metropast is contraindicated in any individual with a history of hypersensitivity to the active ingredient, metronidazole, or any of the inactive ingredients (excipients) used in the formulation.

Age-Specific Eligibility

Use is established and approved for adults and older adults (aged 65 and above). Regulatory documents note that the safety and effectiveness have not been established in pediatric patients (under 18 years).

Conditional Use and Caution

Official labeling mandates that the medicine be used with care in patients who have evidence of, or a history of, blood dyscrasia (e.g., leukopenia) or certain Central Nervous System (CNS) diseases.

Reproductive Status

Use during pregnancy is restricted to situations where it is clearly needed (FDA Category B). Breastfeeding is not recommended during treatment, requiring an official decision regarding discontinuing nursing or discontinuing the drug.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The interaction profile for Metropast is derived from the established effects of the active ingredient, Metronidazole, on the body. Regulatory documents state that interactions are less likely to occur with the topical paste due to minimal systemic absorption; however, the potential for systemic interaction must be considered.

Formal Prohibited Combinations and Timing Rules

Co-administration with Disulfiram is officially contraindicated due to reported psychotic reactions associated with the oral form. Regulatory guidelines require a minimum separation period of two weeks between Disulfiram use and the initiation of metronidazole therapy. Furthermore, the consumption of alcohol (ethanol) or products containing Propylene Glycol is subject to mandatory restriction and requires avoidance during therapy and for at least 24 hours after treatment completion.

Exposure-Modifying Interactions

Interactions with exposure-modifying substances are primarily based on systemic metronidazole data. The combination with Warfarin and other coumarin anticoagulants is documented to potentiate the anticoagulant effect, resulting in a prolongation of prothrombin time due to reduced clearance of the anticoagulant. Similarly, oral metronidazole is associated with elevated plasma lithium concentrations, and interaction with Cimetidine may decrease metronidazole clearance. The drug label also advises caution for patients with severe hepatic impairment or a history of blood dyscrasia.

Mechanism of Action

Metropast's active ingredient functions as a prodrug, which means it is inert until chemically transformed. This transformation, or activation, only occurs inside specific microorganisms (anaerobic bacteria and certain protozoa) that possess the necessary low-oxygen, low-redox potential environment and specific microbial nitroreductase enzymes. This initial step is critical as it dictates the mechanism's inherent selectivity. The mechanism's function relies entirely on the unique metabolic environment within susceptible organisms, rather than interaction with host biological systems.

Once activated, the Metronidazole molecule is rapidly converted into a highly reactive intermediate, the nitro radical anion. This cytotoxic species immediately attacks the pathogen's core genetic material, causing DNA strand breakage and structural fragmentation. This irreparable damage to the microbial DNA halts replication and synthesis, leading swiftly to the death (lysis) of the susceptible organisms.

The entire mechanism is fundamentally constrained by the presence of oxygen. Oxygen competes with the drug for the necessary electrons, thereby inhibiting the activation of the prodrug. Therefore, the mechanism is functionally constrained in well-oxygenated tissues, and any acquired resistance in pathogens is often linked to their ability to limit this essential activation step.

Dosage and Administration Information

How to Use Metropast: Administration Guidelines

Metropast is a specialized topical medication intended solely for external application to the skin, which defines its route of administration and corresponding usage protocol. It must never be used orally, or applied near or into the eyes.

Administration and Dosage Frequency

The frequency of application is determined by the concentration of the prescribed paste. Commonly established regimens for topical metronidazole include:

  • 0.75% Strength: This concentration is typically applied as a thin film to the affected area twice daily, once in the morning and once in the evening.
  • 1% Strength: This concentration is typically applied as a thin film to the affected area once daily.

Usage Protocol and Duration

For proper administration, the area of skin to be treated should first be cleansed using a mild, non-irritating wash. A thin layer of the paste is then applied and gently rubbed into the skin. Non-comedogenic or non-astringent cosmetics may be used after the paste has fully dried.

Treatment duration is standardized, often assessed over an initial course of three to four months. Therapy may be continued for extended periods, such as up to two years, provided clinical benefits are maintained. The course of treatment is typically discontinued if no clear clinical improvement is observed within the established time frames.

Population-Specific Use Rules

Usage guidelines for certain populations are explicitly defined. Older adults use the same standard regimen as younger adults, with no dose adjustment required. Conversely, the safety and effectiveness of this topical formulation have not been established for use in pediatric patients.

Recent Clinical Evidence

Metropast: Recent Clinical Evidence


Evidence for Use in Managing Inflammatory Rosacea Symptoms

Research exploring the use of Metropast, a type of topical metronidazole preparation, includes short-term randomized controlled trials (RCTs), systematic reviews, and a range of other studies. These studies were applied in research contexts involving fluctuating or unstable symptoms of rosacea, focusing on adult patients with moderate to severe papulopustular forms of the condition. Researchers examined outcomes linked to inflammatory or irritative states, such as changes measured in the number of inflammatory lesions (papules and pustules), and the overall condition of the skin assessed by investigators using standardized global assessment scores.

Studies conducted during periods of increased symptom activity have reported that findings describe patterns observed in the studies, particularly concerning changes measured during the study period for inflammatory symptoms. These studies report how symptoms evolved in the observed populations, highlighting changes measured in the number of bumps and pimples over the studied time intervals. This evidence studies contribute to the broader evidence landscape for this condition. Furthermore, research has also explored short-term symptom changes when comparing the active preparation to a non-active vehicle (placebo).

What remains uncertain, however, is the breadth of the research findings. Studies have provided limited insight into the fixed redness (erythema) and the visible small blood vessels (telangiectasias) associated with rosacea. Additionally, while some studies observed responses over defined time intervals that extended to six months to track the maintenance of low symptom activity, long-term effects are not fully established beyond these intermediate durations.


Evidence for Specialized Use in Malodorous Wounds

The research base for the specialized use of topical metronidazole in managing odor associated with chronic skin ulcers is different in nature. This application was studied for patients with wounds characterized by symptoms linked to inflammatory or irritative states. The evidence base here includes systematic reviews, single-arm clinical trials, and a limited number of smaller, controlled trials.

The studies explored outcomes related to physical discomfort, primarily focusing on odor intensity. This was typically measured through patient-reported outcomes describing perceived discomfort and ratings provided by healthcare providers. Data show patterns related to the odor intensity measured when the preparation was observed in these wounds for a short time. Research describes this phenomenon, noting that the study context involved bacteria (anaerobic organisms) commonly linked to odor.


Long-Term Studies and Durability of Effect

The research landscape includes studies that explore short-term symptom changes, typically over a period of up to 12 weeks. These studies report on changes measured during that defined time interval. Beyond this initial phase, some studies explored the persistence of measured changes by monitoring patients to track how symptoms evolved in the observed populations during the maintenance phase. However, as noted in the limitations, there is limited information for long-term outcomes that track patterns of stability and flare-ups well beyond these follow-up periods.


Evidence Gaps and Areas for Future Research

The research provides context but not individual predictions, and the findings describe group patterns, not personal outcomes. A key area where the data remain insufficient is the effect on the vascular manifestations of rosacea. Research describes patterns related to the inflammatory papules and pustules, but the research base provides limited insight into the fixed redness and visible capillaries.

Research is ongoing to better characterize the conditions that were evaluated for this application and to conduct larger trials that use standardized methods for assessing outcomes related to wound odor and microbial presence. These limitations mean that certainty remains low for this application due to the absence of large-scale, consistent trials.

Key Studies & References

  1. Metronidazole Cream/Gel Official Labeling (DailyMed NLM/NIH)
  2. Metronidazole Topical Drug Information (MedlinePlus)

Frequently Asked Questions (FAQ)

Common questions about Metropast (FAQ)


Q: How quickly can someone expect Metropast to start working?

Studies and official information indicate that most initial measured changes in inflammatory symptoms are observed within the first three weeks of using the preparation. However, the full course of therapy is typically assessed over a duration of three to four months.

Q: Does Metropast treat all types of the condition, or just certain ones?

Regulatory documents state that this preparation is indicated for the topical treatment of the inflammatory lesions of rosacea. Its defined use specifically targets symptoms like papules and pustules.

Q: How long do the effects of Metropast last after taking it?

According to the official product information, the frequency of application is set by the prescribed regimen. This regimen is designed to maintain a consistent concentration of the medication on the skin throughout the day and night.

Q: Can Metropast interact with common vitamins or supplements?

Official guidelines require that all medicines and supplements be discussed with a healthcare provider. While no specific warnings exist for most common vitamins, caution is advised with liquid supplements that may contain alcohol.

Q: What happens if I stop using Metropast suddenly?

Rosacea is noted in official information to be a condition that may respond slowly to treatments. Treatment courses are established to optimize resolution of symptoms. If treatment is ceased before the recommended period, symptoms may potentially recur or not fully resolve.

Q: Is Metropast available in a generic version?

The active ingredient in this preparation is metronidazole. Topical metronidazole is available to patients not only under various brand names but also in generic formulations.

Q: Are there any restrictions on driving or operating machinery while taking Metropast?

Due to the topical nature of the preparation and its generally low absorption into the bloodstream, the risk of it affecting coordination is considered low. Regulatory information notes that if abnormal neurologic signs are experienced, it is important for the patient to seek medical attention.

Q: Why do official documents refer to Metropast as a certain class of medicine?

The active ingredient in Metropast is classified in official documents as a nitroimidazole. This is a type of antimicrobial medicine.

Q: Do I need to change my lifestyle while taking Metropast?

Official regulatory documents require the avoidance of alcohol consumption while using this preparation. Additionally, regulatory information includes precautions about strong sunlight and prolonged exposure to ultraviolet light, which should be reviewed by the patient.

Q: What is the experience of people who have been using Metropast for a long time?

While clinical studies often focus on short to intermediate durations, regulatory documents do note that the potential for systemic effects, such as peripheral neuropathy (numbness or tingling), is associated with cumulative or long-term exposure to the active drug substance.

Q: What should I do if I miss a dose of Metropast?

Official patient information contains guidance for managing missed applications. This guidance typically describes the steps for applying a forgotten dose, while explicitly stating that doubling the amount should be avoided.

Q: Can Metropast be used if I am currently taking pain relievers?

Regulatory drug interaction documents do not list common pain relievers as a specific known interaction with this topical preparation. Official guidelines require that a healthcare provider be made aware of all medicines being taken.

Q: Are allergic reactions to Metropast common?

The medication is officially contraindicated for people with a known history of hypersensitivity (allergic reactions) to metronidazole or any of its ingredients. Allergic reactions have been reported, primarily through post-marketing experience.

Q: What is the general advice about what to do if a side effect occurs?

Official documents mandate that if severe skin reactions, numbness, pain, or tingling in the extremities (peripheral neuropathy), or any new or worsening symptoms are experienced, the patient must seek medical attention.

Q: Can people with kidney issues take Metropast?

Studies indicate that decreased kidney function does not significantly change how the active ingredient is processed by the body following topical application. However, general caution is advised in regulatory documents for patients undergoing dialysis.

Q: What does 'contraindication' mean in relation to Metropast?

According to official product labeling, a contraindication is a circumstance or condition where the use of the drug is officially advised against. This is because using the medicine under these conditions may carry a potential risk of harm.

Q: Are there different forms (tablet, liquid, etc.) of Metropast available?

The active ingredient in this preparation, metronidazole, is available in multiple forms. These include various topical options such as gels, creams, and lotions, as well as other formulations used for oral or vaginal administration.

Q: Does Metropast interfere with birth control or hormone therapy?

Due to its topical application, the preparation has minimal absorption into the bloodstream. However, oral forms of the active ingredient have been reported to potentially reduce the effectiveness of some estrogen-containing contraceptives.

Q: What clinical trials led to Metropast's approval?

Regulatory approval was based on evidence gathered from clinical studies, including randomized controlled trials. These trials specifically examined the effects of the topical formulation on the inflammatory lesions associated with rosacea.

Q: Are there any known long-term effects of taking Metropast for several years?

The official labeling notes that the risk of serious systemic effects, such as peripheral neuropathy (which involves numbness or tingling), is associated with the potential for cumulative or extended exposure to the drug substance over time.

Q: How is Metropast’s safety classification described by the FDA or EMA?

Some global regulatory authorities have assigned the drug substance a safety designation of Pregnancy Category B. This classification is descriptive and refers to the findings from studies in pregnant animals.

Q: Why is Metropast not recommended for people who are pregnant?

The product label contains a strong precaution that use during pregnancy must be carefully considered and evaluated against the clinical need. This caution is based on the fact that the active ingredient, metronidazole, is known to cross the placenta when taken in its oral form.

Q: Is Metropast a medication that requires close monitoring?

Official warnings indicate that patients who have a history of blood dyscrasia (a blood cell disorder) or severe hepatic impairment (liver disease) require careful monitoring during therapy. This is due to the potential systemic effects associated with the drug substance.

Q: Is there any information about Metropast and sun sensitivity?

Regulatory documents include a precaution stating that unnecessary or prolonged exposure to strong sunlight, including tanning beds or sun lamps, should be avoided while the preparation is in use.

Q: What are the rules regarding combining Metropast with herbal products?

There are no specific known problems reported with combining this topical treatment with herbal remedies. However, caution is advised concerning any liquid herbal product formulations that may contain alcohol.

Q: Is Metropast ever used alongside other specific medications for the same condition?

Research has explored the use of the preparation to help maintain symptom reduction after successful treatment with other systemic medications. For example, some studies have examined its use following a course of oral tetracyclines.

Q: What is the official definition of the condition Metropast is intended to treat?

Metropast is officially indicated in regulatory documents for the topical treatment of the inflammatory lesions of rosacea.

Q: What is the shelf life or stability of Metropast?

Official product information specifies the shelf life for the unopened product. It may also provide a defined time frame, such as 28 days, for how long the preparation should be used once the package has been opened.

Q: Does Metropast cause changes in mood or sleep patterns?

Changes in mood or sleep patterns are not among the frequently reported side effects for the topical form. However, the experience of central nervous system effects, such as headache, is required by regulatory documents to be reported to a healthcare provider.

Q: What does the term 'off-label use' mean and is it relevant to Metropast?

Off-label use is defined as prescribing a medicine for a purpose or in a manner that is not specified in the official regulatory documents that granted its approval. This document focuses only on the officially recognized indications.

Q: Is Metropast a first-line treatment, or is it used later in therapy?

Research has described this preparation as being significantly effective compared to a non-active vehicle (placebo) when used in the initial treatment of moderate to severe inflammatory rosacea symptoms. It is often a consideration for patients who prefer topical therapy.

How should Metropast be stored and disposed of?

How to Store and Dispose of Metropast

The storage and disposal of Metropast (metronidazole topical paste) must follow specific conditions established in official governmental labeling to maintain product stability and ensure safety.

Storage Requirements

Condition Requirement
Temperature Store at Controlled Room Temperature, typically 15 C to 30 C (59 F to 86 F).
Protection Protect from freezing; the product must not be refrigerated or frozen.
Container Keep the container tightly closed and store the medication in the container it was dispensed in.
Child Safety The medication must be kept out of reach of children.

Disposal Instructions

Unused or expired Metropast should not be flushed down a toilet or poured down a sink. The official disposal procedure involves mixing the unused product with an undesirable substance, such as dirt or used coffee grounds, and placing the mixture in a sealed bag before disposal in the household trash.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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