Resflor

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Resflor

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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 Resflor

What is Resflor: Definition and Pharmacological Classification

Resflor is a prescription-only veterinary pharmaceutical formulated as a combination drug specifically developed for use in bovine (cattle). It is classified simultaneously as an Antimicrobial agent and a Non-Steroidal Anti-Inflammatory Drug (NSAID). This dual-action approach is intended for the initial management of acute bacterial diseases.

Property Description
Active ingredients Florfenicol, Flunixin meglumine
Form Sterile Injectable Solution
Pharmacological class Phenicol Antibiotic, Fenamate NSAID
Primary action Anti-infective and Anti-inflammatory
Origin Synthetic Compound

Composition, Form, and Origin

The product’s core efficacy is derived from its two distinct active ingredients: Florfenicol and Flunixin meglumine. Florfenicol is a synthetic compound belonging to the phenicol class of antibiotics, distinguishing it from beta-lactam antibiotics. The preparation is provided as a sterile injectable solution, a dosage form used in veterinary medicine to ensure systemic concentrations. The formulation is intended for parenteral administration in cattle, where the active agents are dissolved within a sterile aqueous or oily vehicle.

General Purpose: Why Florfenicol and Flunixin are Combined

The fundamental purpose of combining these agents is to deliver a simultaneous attack on the pathogen and supportive care for the animal's systemic health. Flunixin, the NSAID component, serves to mitigate the acute inflammatory and pyrexic (fever) responses associated with infection. This means the product is designed to control the bacterial infection via Florfenicol while managing the clinical manifestations of the illness to support the overall comfort and stability of the animal.

Regulatory References

  1. FDA FOI Summary for RESFLOR GOLD (NADA 141-299)

What side effects are possible with Resflor?

Possible Side Effects and Safety Information

The medicine's safety profile is documented across official regulatory sources, classifying potential adverse reactions by frequency and physiological system. The safety data includes limitations regarding pre-existing conditions and use in specific animal populations.

Officially Documented Adverse Reactions

The following effects are listed in regulatory documents based on the affected System-Organ Class (SOC) and documented frequency:

Adverse Event Frequency Classification System-Organ Class (SOC)
Injection site swelling Very Common General disorders and administration site conditions
Anaphylactic-type reaction Very Rare Immune system disorders
Transient inappetence Not Formally Classified Gastrointestinal disorders
Diarrhea Not Formally Classified Gastrointestinal disorders

Injection site swelling is the most frequently documented effect, typically becoming palpable 2–3 days after administration and lasting for approximately 15 to 36 days. The anaphylactic-type reaction is classified as Very Rare and is noted as potentially fatal.

Safety-Related Restrictions

Official labeling outlines strict contraindications related to the NSAID component, Flunixin meglumine. The product is restricted from use in animals with pre-existing hepatic, renal, or cardiac diseases, or those with risk of gastrointestinal bleeding or altered hemostasis. It is also contraindicated for use in adult bulls intended for breeding and must be avoided in dehydrated, hypovolaemic, or hypotensive animals due to the potential for increased renal toxicity. Concurrent use with other NSAIDs or glucocorticosteroids is restricted due to the risk of additional adverse effects.

Overdose and Emergency Response

The official regulatory documentation for Resflor details the expected clinical presentations and mandated emergency actions following excessive exposure. Overdose studies have documented significant clinical signs, including decreases in food consumption and water intake, leading to a measurable reduction in body weights. Furthermore, severe pathological outcomes were recorded in prolonged, high-dose scenarios, characterized by the development of erosive and ulcerative lesions in the abomasum.

The prescribing information highlights specific risk factors for heightened toxicity due to the NSAID component, Flunixin meglumine. There is an increased potential for renal toxicity in animals that are already experiencing conditions of dehydration, hypovolaemia, or hypotension. Excessive exposure may also pose the risk for systemic complications, including hepatic and hematologic effects, which are recognized class risks documented by regulatory authorities.

When Immediate Medical Help Is Required

A critical emergency action mandated by the official labeling pertains to human safety: Accidental injection requires that individuals consult a physician immediately. For a suspected overdose in the target species, immediate emergency medical care must be sought. No specific antidote is documented; therefore, official intervention is based solely on symptomatic and supportive treatment to manage the specific documented clinical signs.

Therapeutic Uses of Resflor

What Resflor Treats: Main Uses and Benefits

The medication is applied across domains where additional symptomatic support is needed during acute or disruptive episodes. This is commonly used across conditions presenting with acute episodes and helps address symptom clusters that may become intense or disruptive. The medication is relevant for easing symptoms primarily associated with Bovine Respiratory Disease (BRD), serving as an adjunctive treatment for symptomatic management.

The product is used for the treatment of BRD and the control of BRD-associated pyrexia. The therapeutic areas include managing fever, pain, and acute inflammation.

Resflor is commonly used when short-term symptomatic assistance is needed, as it supports the patient during difficult episodes by easing distress. The medication is applied in addressing symptoms related to systemic imbalance (fever) and symptoms related to inflammatory or irritative states (pain/inflammation).

“This supportive relief contributes to improved comfort during periods of heightened symptoms.”

It is applied in clinical settings that involve acute or unstable symptom patterns, where the medication may assist with maintaining functional stability when symptoms are more noticeable.


Quick Fact: Relevant for Easing Pyrexia and Discomfort

Regulatory References

  1. FDA Freedom of Information Summary

Eligibility and Restrictions for Use

Who Can and Cannot Use Resflor: Official Eligibility

Resflor is officially designated for use exclusively in beef cattle and non-lactating dairy cattle, as established by regulatory documents. The official eligibility profile sets specific, non-negotiable limitations based on the animal's production status, age, and existing health conditions.

Contraindicated Populations

Use is absolutely contraindicated in animals with known hypersensitivity to florfenicol or flunixin. The product is strictly prohibited in female dairy cattle 20 months of age or older (including dry cows) and in calves to be processed for veal due to residue concerns. Adult bulls intended for breeding purposes are also contraindicated.

Condition-Based Exclusions

The label mandates absolute non-eligibility for animals suffering from underlying organ dysfunction, specifically hepatic diseases, renal diseases, or cardiac diseases. Use is also contraindicated in animals with evidence of altered hemostasis or a risk of gastrointestinal bleeding.

Special Populations

Safety has not been established for calves of 3 weeks of age or less or in cattle during pregnancy or for breeding purposes. Additionally, use should be avoided in dehydrated, hypovolaemic, or hypotensive animals due to potential risk factors.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Resflor contains the non-steroidal anti-inflammatory drug (NSAID) Flunixin meglumine, and its interaction profile is structured around the official restrictions necessary to prevent additive toxicity. All documented interaction information is based strictly on regulatory prescribing documents.

Contraindicated Combinations and Mandatory Restrictions

Co-administration with certain substance classes is formally prohibited due to the risk of increased adverse effects:

  • Other NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) are contraindicated.
  • Glucocorticosteroids are contraindicated due to the potential for exacerbating gastrointestinal tract ulceration.
  • Concurrent administration with potentially nephrotoxic drugs should be avoided due to the documented risk of increased renal toxicity.

Pharmacodynamic and Timing Constraints

Interactions also occur with other protein-bound substances and prior treatments. Administration with active substances with a high degree of protein binding may lead to a competitive interaction, potentially resulting in toxic effects. Furthermore, a treatment-free period of at least 24 hours must be observed following the cessation of any other anti-inflammatory substances before commencing treatment with Resflor.

Physiological State-Driven Interaction Notes

The interaction risk is documented to be heightened by the animal's physical state. Use should be avoided in dehydrated, hypovolaemic, or hypotensive animals due to the potential for increased renal toxicity. Similarly, patients with existing renal, cardiovascular, and/or hepatic dysfunction are noted to be at greatest risk for adverse events from the NSAID component.

Mechanism of Action

Resflor is a fixed-dose combination product containing two distinct pharmacologic agents: florfenicol and flunixin meglumine.

Florfenicol functions as a bacteriostatic inhibitor of microbial protein synthesis. It selectively targets and binds to the 50S subunit of the bacterial 70S ribosome. This molecular interaction spatially inhibits the peptidyl transferase enzyme, thereby disrupting the elongation of peptide chains and arresting the production of essential microbial proteins.

Flunixin meglumine is a non-steroidal anti-inflammatory drug that acts as a reversible, non-selective inhibitor of the cyclooxygenase (COX) enzyme system, encompassing both COX-1 and COX-2 isoforms. Inhibition of COX blocks the conversion of arachidonic acid to cyclic endoperoxides. This molecular pathway modulation decreases the systemic biosynthesis of eicosanoids, specifically prostaglandins (PGE2).

Consequent system-level physiological effects include a reduction in eicosanoid-mediated inflammatory processes and inhibition of PGE2 synthesis within the hypothalamus, the central thermoregulatory center.

Dosage and Administration Information

How Resflor is Used: Administration Guidelines

Resflor is administered via a standardized administration protocol. This protocol specifies the administration route, dosing regimen, and procedural constraints necessary for use.


Administration Protocol Summary

Feature Instruction Summary
Route of Administration Subcutaneous (SQ) injection only.
Dosing Schedule A single injection calculated by body weight (BW).
Dose Rate 6 mL per 100 lbs BW.
Frequency One-time use only (single-course treatment).
Injection Site Limit Do not administer more than 10 mL at any single injection site.
Injection Location Must be given only in the neck region.

Use Conditions and Procedural Steps

Dosing Requirements and Restrictions

To ensure the delivery of the mg/kg rate for both active ingredients, the animal's body weight must be determined as accurately as possible prior to administration. The product is labeled for use in beef cattle and non-lactating dairy cattle. It is not for use in female dairy cattle 20 months of age or older, or in calves intended for veal processing.

Procedural Follow-up

As a single-dose treatment, the clinical status of the animal should be evaluated 48 to 72 hours after the injection. If clinical signs associated with the condition persist or worsen during this evaluation window, treatment should be changed to an appropriate, alternative therapy.

Recent Clinical Evidence

Research evidence / Overview of studies for Resflor

Evidence for Use in Bovine Respiratory Disease (BRD) Treatment

Research examining Resflor for conditions associated with Bovine Respiratory Disease (BRD) has been conducted using randomized, comparative field trials. These are studies that compared the effects of the combination product against the antibiotic component (Florfenicol) used alone, or against other established protocols. This research was studied for conditions characterized by bacterial infections involving specific pathogens like Mannheimia haemolytica and Pasteurella multocida. The study populations included calves or juvenile cattle exhibiting severe signs of naturally occurring respiratory disease.

Studies tracked outcomes related to systemic or functional imbalance by measuring standardized scores of clinical signs, such as appetite changes, depression, and respiratory distress. These findings describe patterns observed in the studies, reporting how these symptoms evolved in the observed cattle populations.

Evidence for the Control of BRD-Associated Fever (Pyrexia)

Dedicated research has explored the use of the combination product for outcomes capturing phases of heightened symptom activity, specifically the management of BRD-associated fever (pyrexia). These studies compared the combination product, which includes an NSAID, against the antibiotic-only formulation. The primary goal of this research was to examine temporary physiological imbalance.

Researchers primarily monitored physiological strain or stress by measuring the change in rectal temperature from the baseline reading taken before treatment began. Findings indicate patterns related to temperature changes, with studies reporting how fever measurements evolved in the observed populations during the initial hours and days following administration.

Research Gaps and Uncertainties

While research provides context on short-term efficacy for the approved indications, several key limitations were noted in regulatory and scientific reviews. First, follow-up durations focused on short-term observation intervals. Secondly, data for certain groups remain insufficient; the research base has limited information on calves under 3 weeks of age. Furthermore, there is limited information regarding the use of the product in cattle of breeding age, during pregnancy, or while lactating, meaning results apply only to the non-breeding, non-lactating populations studied.

Key Studies & References FDA Freedom of Information Summary (FOI/864): Efficacy and Safety Trials for Florfenicol and Flunixin Meglumine

Frequently Asked Questions (FAQ)

Common questions about Resflor (FAQ)


Q: How long does it typically take for Resflor to start working?

Official documents advise that the anti-inflammatory component can quickly reduce fever, which might temporarily mask the underlying bacterial response. For this reason, official guidelines note an evaluation of the full response and overall clinical status occurs mathbf48 to mathbf72 hours after the single injection.


Q: Why do some forums say Resflor is hard to get?

According to official regulatory labeling, Resflor is classified as a mathbfprescription mathbfonly veterinary drug. This means the product is restricted by law to use only under the direction or order of a licensed veterinarian, which may limit its availability to the general public.


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

A mathbfcontraindication is a strict medical condition under which the product is mathbfstrictly mathbfprohibited for use in the animal. Official information states that the product is contraindicated for animals with pre-existing conditions like hepatic (liver) or renal (kidney) disease, or a known hypersensitivity to the ingredients.


Q: Can Resflor interact with herbal supplements?

The regulatory label describes potential interactions with active substances that have a mathbfhigh mathbfdegree mathbfof mathbfprotein mathbfbinding. While herbal supplements are not specifically listed by name, these types of products could potentially interact with the flunixin component, which is noted to increase the risk of adverse effects.


Q: Does the research on Resflor include diverse patient groups?

Official research summaries indicate that safety and effectiveness have mathbfnot mathbfbeen mathbfestablished across all potential populations. This includes limited information for calves 3 weeks of age or less, as well as cattle during pregnancy, while lactating, or those intended for breeding purposes.


Q: Can Resflor interact with over-the-counter cold medications?

The official product information states that concurrent use with other mathbfanti mathbfinflammatory mathbfdrugs, such as other Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) or corticosteroids, is advised by official information to be avoided or closely monitored. Although human cold medications are not specifically detailed, their ingredients may fall into these restricted categories.


Q: What is the shelf life of Resflor?

According to the official pharmaceutical particulars, the shelf life of the mathbfunopened product is typically mathbf2 mathbfyears. Once the container is opened for the first time, the solution is indicated for use within mathbf28 mathbfdays to maintain stability.


Q: How long does Resflor stay in your system after stopping use?

Pharmacological studies, as described in the official product information, provide data on how the active ingredients are eliminated from the system. For the antibiotic component (florfenicol), the mean terminal half-life is approximately mathbf28.5 mathbfhours.


Q: Is Resflor known to cause weight gain or loss?

Official documents do not list weight gain as a known effect at the recommended dose. Overdose studies that administered high doses showed mathbfdecreased mathbffood mathbfconsumption and mathbfdecreased mathbfbody mathbfweights in treated animals.


Q: Can older adults use Resflor safely?

Official documents frame safety based on the animal's physical health, rather than just age. The key restriction is that patients with existing renal (kidney), cardiovascular (heart), or hepatic (liver) dysfunction are noted to be at the greatest risk for adverse events from the NSAID component.


Q: What kind of monitoring (like blood tests) is sometimes needed with Resflor?

Official precautions advise that the concurrent administration of potentially mathbfnephrotoxic (kidney-damaging) drugs is noted to require careful monitoring due to the risk of increased renal toxicity. While monitoring is advised, the regulatory label does not specify the exact type of procedure (such as blood tests) that must be performed.


Q: Does Resflor affect the results of common laboratory tests?

The official caution notes that the NSAID component belongs to a class of drugs where mathbfhematologic (blood-related) effects have been reported, which may influence laboratory test results related to blood components.


Q: Are there common signs of too much Resflor being used?

Information gathered from official overdose studies identifies signs of excessive exposure. These signs included decreased food and water consumption, which resulted in decreased body weight, as well as the observation of dose-related erosive and ulcerative lesions in the abomasum (a part of the stomach).

How should Resflor be stored and disposed of?

How to Store and Dispose of Resflor

The storage and disposal of Resflor (Florfenicol and Flunixin Meglumine Injection) must adhere to the mandatory requirements defined in official regulatory labeling to ensure stability and safety.

Storage Conditions

  • Temperature Restrictions: Store the product below the maximum temperature of 30 C or 25 C (depending on the regional label). The product must not be frozen and should be protected from frost.
  • Packaging: The vial must be kept in the outer carton. For the 500 mL vial, the rubber stopper should not be punctured more than 20 times.
  • Stability: After the first use, the solution must be used within 28 days.
  • Child Safety: The product must be kept out of the sight and reach of children.

Disposal Requirements

Unused or expired product and related waste materials must be disposed of strictly according to local environmental regulations. The label prohibits disposal via wastewater or general household waste.

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

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