ZACTRAN

Gamithromycin

Treatment option:

Medically reviewed

Last updated on 10/01/2026

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 ZACTRAN

Property	Description
Active Ingredient	Gamithromycin
Form	Sterile parenteral solution (Injectable)
Pharmacological Class	Macrolide Antibiotic (Azalide)
General Purpose	Anti-infective (Combatting bacterial growth)
Origin	Semi-synthetic

ZACTRAN is a specialized veterinary medicine defined as a powerful anti-infective agent used for the management of bacterial diseases in susceptible livestock. Its fundamental purpose is to support animal health by providing effective treatment and prevention of bacterial infections.

What Type of Antimicrobial is ZACTRAN?

ZACTRAN is classified as a macrolide antibiotic, with its active ingredient being Gamithromycin. This drug belongs more specifically to the azalide antimicrobial sub-class. Gamithromycin is a semi-synthetic compound, meaning it is chemically derived from a natural macrolide precursor to optimize its properties. Its classification as an antimicrobial confirms its role is to target and manage the growth of susceptible bacterial pathogens.

Composition and Form: The Injectable Solution

The product is supplied as a sterile parenteral solution, which is a ready-to-use injectable solution administered via the parenteral route, primarily in cattle and, in some jurisdictions, pigs and sheep. The composition is standardized to contain 150 mg of Gamithromycin as the free base per milliliter of solution. The active substance is dissolved in a glycerol formal solvent vehicle, along with stabilizing excipients like succinic acid, which is necessary to maintain the solution's stability and ensure the reliable delivery of the drug. The injectable format is intended for achieving rapid and highly available therapeutic levels after a single injection.

How Does Gamithromycin Generally Help Resolve Infection?

Gamithromycin helps resolve bacterial infections by acting as a protein synthesis inhibitor within the bacterial cell, which is its high-level mechanism of action. Specifically, it achieves its antibacterial effect by binding to the 50S ribosomal subunit of the bacteria, thereby obstructing the process of protein construction critical for the pathogen's ability to grow and replicate. This inhibition primarily stops the infection from advancing, enabling the animal's own immune defenses to clear the remaining bacteria and achieve the resolution of the bacterial disease.

Regulatory References

DailyMed

What side effects are possible with ZACTRAN?

Possible Side Effects and Safety Information

The safety profile of ZACTRAN (Gamithromycin) is based on official classifications from regulatory documents, primarily defining adverse events by their location and frequency.

Frequency-Classified Adverse Reactions

The incidence of documented effects is categorized according to established regulatory standards:

Very Common: Local reactions at the injection site are the most frequently observed events. These include swelling, heat, tenderness, and the formation of a firm lump or nodule at the site of administration.
Common: The experience of transient pain or slight swelling immediately following the injection.
Uncommon: Adverse reactions involving the immune system, specifically hypersensitivity reactions.

These effects are classified within the General disorders and administration site conditions and Immune system disorders System-Organ Classes.

Regulatory Safety Constraints

Official labeling defines specific constraints and limitations necessary for safe use:

Contraindication: The medicine is prohibited for use in animals with a known history of hypersensitivity to macrolide antibiotics.
Route Prohibition: ZACTRAN must not be administered intravenously (IV).
Population Limits: Safety has not been established for use in breeding bulls, and the product is not approved for use in veal calves.

The official documentation notes that both the pain and slight swelling are typically transient (short-lived). These regulatory limitations and frequency classifications collectively structure the officially recognized risk profile of Gamithromycin.

Overdose and Emergency Response

Overdose and When to Seek Help

The official regulatory documents for ZACTRAN (Gamithromycin) establish a clear profile regarding overexposure. Studies conducted in the target species (cattle, sheep, and pigs) demonstrated a wide margin of safety when the product was administered at doses up to five times the therapeutic recommendation.

Documented Overdose Manifestations

Overdose manifestations in the target animal species are primarily confined to the injection site. The documented clinical signs observed in regulatory trials include localized swelling, transient pain, and inflammation. These local reactions are officially classified as dose-related, meaning their intensity increases proportionally with the amount of medication administered. Regulatory documents do not describe systemic, severe, or life-threatening outcomes such as cardiovascular or central nervous system effects following high-dose exposure in the target animals. No specific antidote for Gamithromycin is known or specified in the official regulatory documentation.

Emergency Action for Human Exposure

The most critical regulatory instruction is reserved for accidental human exposure. The label mandates that any person who sustains an accidental self-injection or accidental ingestion of this veterinary medicine must seek medical advice immediately. It is also a mandatory instruction to show the product packaging or label to the treating physician. Management for human overexposure is advised to be symptomatic treatment.

Therapeutic Uses of ZACTRAN

The therapeutic application of ZACTRAN is commonly used to help manage symptoms related to physical discomfort and systemic imbalance in livestock.

Management of Acute Bacterial Respiratory Disease

ZACTRAN is applied in addressing conditions associated with bacterial infection, including Bovine Respiratory Disease (BRD) in cattle and Swine Respiratory Disease (SRD) in pigs. These are conditions characterized by periods of heightened symptoms such as fever and respiratory distress. The medication is relevant for managing these symptoms, which may create noticeable physiological strain. This use supports the patient during difficult episodes by easing physical discomfort and strain.

Contexts of Use and Supportive Benefits

The medication is also relevant in high-risk scenarios, specifically for the control of respiratory disease in cattle highly susceptible to developing BRD. This application provides support that contributes to easing the overall symptom load in a herd setting and assists with maintaining functional stability. Furthermore, ZACTRAN is commonly used to address Infectious Pododermatitis (Foot Rot) in sheep, supporting general well-being during symptomatic phases by easing distress related to mobility.

Quick Fact: Relief for Acute Systemic Symptoms ZACTRAN is considered relevant in contexts involving heightened systemic burden and for supporting the management of fever and labored breathing associated with bacterial respiratory disease.

Regulatory References

U.S. Food and Drug Administration's Freedom of Information Summary

Eligibility and Restrictions for Use

Who Can and Cannot Use ZACTRAN?

ZACTRAN (Gamithromycin) is a veterinary medicine with eligibility rules strictly defined by regulatory agencies.

Populations Permitted to Use:

Cattle: Beef cattle and non-lactating dairy cattle.
Other Species: Approved for use in pigs and sheep in certain jurisdictions for specific respiratory or foot conditions.

Populations Prohibited from Use (Contraindicated):

Animals with a known history of hypersensitivity to Gamithromycin, any excipient, or the macrolide class of antibiotics.
Animals receiving simultaneous treatment with other macrolide or lincosamide antimicrobials.
The product is strictly Not For Use In Humans.

Key Restrictions and Limitations:

Age/Production: Use is prohibited in female dairy cattle 20 months of age or older and in calves intended to be processed for veal.
Milk Production: It is not authorized for use in any animals producing milk for human consumption.
Pregnancy/Lactation: Safety in these states has not been established. Use is permitted only following a formal risk/benefit assessment by the responsible veterinarian.

What should I know about interactions with other medicines?

Interactions with Other Medicines and Products

This section summarizes the official interaction information for ZACTRAN (Gamithromycin) as documented in authoritative regulatory sources.

Documented Interaction Restrictions

Interactions with ZACTRAN are primarily based on pharmacodynamic constraints and the necessity to avoid combinations that could lead to reduced effectiveness or increased resistance.

Contraindicated Combinations The simultaneous use of ZACTRAN is prohibited with antimicrobials that share a similar mechanism of action, due to the potential for cross-resistance and antagonism. Regulatory documents specifically state the following:

Other Macrolides
Lincosamides

These restrictions are based on the risk of cross resistance among drug classes.

Procedural Incompatibility

Official labeling includes a restriction regarding the physical mixing of the product.

Mixing Prohibition: ZACTRAN should not be mixed with any other veterinary medicinal products in a syringe or container unless compatibility studies have explicitly confirmed the mixture's stability and integrity.

Exposure Modification and Other Interactions

Regulatory information does not list specific interacting medicines that significantly alter the drug's systemic exposure (AUC/Cmax) through metabolic pathways (e.g., CYP enzymes) or drug transporters (e.g., P-gp). There are no specific timing-based dosing rules, and no interactions with food, alcohol, or herbal products are documented in the official regulatory profile.

Mechanism of Action

The mechanism of ZACTRAN (Gamithromycin) is centered on two distinct biological effects: the direct interference with bacterial life processes and the modulation of the host's inflammatory response. The combined actions result in the cessation of bacterial proliferation and modulation of the host's local inflammatory response.

Targeting Bacterial Protein Synthesis and Replication

Gamithromycin works by highly selective and reversible binding to the 50S ribosomal subunit of susceptible bacteria, specifically targeting the 23S ribosomal RNA. This action blocks the translocation step required for polypeptide chain elongation, thereby inhibiting the synthesis of essential structural and functional bacterial proteins. The molecular interference leads directly to the primary physiological consequence: the cessation of bacterial proliferation (bacteriostasis).

Sustained Tissue Presence and Immune Pathway Modulation

The molecule also engages mechanisms that affect the host's tissue dynamics, resulting in a prolonged tissue concentration by accumulating inside local immune cells like neutrophils and macrophages. Furthermore, it acts as a modulator of local inflammatory pathways, helping to dampen the excessive migration of immune cells and reducing the release of pro-inflammatory mediators. This secondary action modulates the inflammatory cascade, complementing the core antibacterial mechanism and supporting a more regulated physiological state in the affected tissue.

Dosage and Administration Information

How ZACTRAN is Used: Official Administration Guidelines

The official guidelines for using ZACTRAN (Gamithromycin) establish a single, weight-dependent administration of the injectable solution, strictly defining the route and physical constraints of delivery. The medication is a ready-to-use sterile parenteral solution supplied at a concentration of 150 mg of Gamithromycin per milliliter.

Administration Scope

The standard administration requires a single dose of 6 mg per kg of the animal’s body weight, equivalent to 1 mL per 25 kg body weight. This regimen defines the complete course of therapy, as no subsequent or repeat dosing is specified in the official instructions.

Feature	Official Instruction
Route of administration	Administered by subcutaneous injection (SC) in cattle or intramuscular injection (IM) in pigs and sheep.
Preparation requirements	Ready-to-use solution; no prior dilution or mixing is required.
Age-group administration rules	The dose is calculated based on the actual weight of the animal for all approved species.
Special procedural conditions	Must not be administered intravenously. Volume restrictions apply: Max 10 mL per SC injection site in cattle; Max 5 mL per IM injection site in pigs and sheep.

Resulting Procedural Structure

The use protocol requires a precise sequence to ensure proper dosing. First, the actual body weight of the animal must be determined to calculate the total required volume based on the 6 mg/kg regimen. This calculated volume is then delivered as a single injection via the designated route (SC or IM). The final step involves ensuring the total dose is correctly distributed, adhering to the 10 mL or 5 mL volume limit per injection site.

This protocol governs the method and quantity for delivering the single therapeutic dose.

Recent Clinical Evidence

Research evidence / Overview of studies for ZACTRAN

Evidence for use in Bovine Respiratory Disease (BRD)

Research exploring Gamithromycin was conducted through Randomized Controlled Trials (RCTs) and large-scale Clinical Field Studies. These studies were applied in research exploring how symptoms change over time in two primary scenarios: treating individual animals that show clinical signs of BRD, and research exploring the use of Gamithromycin for control (metaphylaxis) in high-risk groups of cattle susceptible to developing the disease.

Researchers focused on outcomes related to physical discomfort and systemic imbalance, such as fever, depression, and difficulties with breathing. They also closely monitored re-treatment rates and case-fatality rates over a specified period. The findings describe patterns observed in these studies, where clinical signs and overall health status were monitored for several days following the start of treatment.

Despite the body of research, data for long-term outcomes remain insufficient because the trials were not designed to track status over the animal's full lifespan. While drug concentration in lung tissue was monitored in some studies, there is limited information for outcomes related to chronic respiratory health or the durability of the measured response.

Evidence for use in Swine Respiratory Disease (SRD)

For the treatment of Swine Respiratory Disease (SRD) in pigs, clinical evaluation was performed mainly through multicenter European Field Studies. These studies often used an active control to examine the measured clinical outcomes of Gamithromycin.

Key Studies & References

Frequently Asked Questions (FAQ)

Common questions about ZACTRAN (FAQ)

Q: Is ZACTRAN the same kind of drug as [Similar Drug Name]?

ZACTRAN’s active ingredient, Gamithromycin, is classified as a macrolide antibiotic, belonging specifically to the azalide sub-class. Official regulatory information places it in the same general class of antimicrobials as other macrolides, which are known for disrupting bacterial protein synthesis.

Q: What is the main difference between ZACTRAN and other treatments for this condition?

As a long-acting azalide macrolide, Gamithromycin is chemically engineered to achieve high and sustained concentrations in target tissues like the lungs and bronchial fluid. This characteristic is associated with a regimen that is typically administered as a single injection.

Q: Do you need a special prescription for ZACTRAN?

Yes. ZACTRAN is classified as a Prescription Animal Drug by regulatory bodies like the FDA and EMA. This means that federal or national law requires its use to be by or on the order of a licensed veterinarian.

Q: Does ZACTRAN show up on drug tests?

The drug is associated with residues in the animal's edible tissues. Regulatory agencies establish a withdrawal period (e.g., 35-64 days, depending on the label and jurisdiction) during which the animal cannot be slaughtered for human consumption to ensure residues are below safe limits.

Q: Can ZACTRAN be taken with common vitamins like Vitamin D or B12?

Official information does not specifically list interactions with common vitamins. However, regulatory documents state that ZACTRAN should not be mixed with any other injectable veterinary medicinal products in a syringe unless compatibility has been confirmed.

Q: What does the box warning or black box warning for ZACTRAN mean?

ZACTRAN does not carry a Black Box Warning in its official US or EU regulatory labeling. The highest-level safety constraint listed is a contraindication, which prohibits its use in animals with a known hypersensitivity or allergic reaction to macrolide antibiotics.

Q: How long does ZACTRAN stay in your system after stopping it?

While the drug's half-life (the time it takes for the concentration to reduce by half) in the bloodstream is approximately 3-4 days in cattle, the relevant regulatory measure is the withdrawal period. This period—ranging from 16 to 64 days depending on the species and jurisdiction—is the time required for the drug's residues to clear the animal’s tissues for meat safety.

Q: Is ZACTRAN a relatively new medicine?

ZACTRAN (Gamithromycin) received its first major market authorization in the European Union in July 2008. This places it among the newer generation of long-acting macrolide antibiotics specifically developed for use in veterinary respiratory medicine.

Q: Do people develop a tolerance to ZACTRAN over time?

The official product information includes a statement regarding the potential for cross resistance with other macrolides. This means that bacteria resistant to one macrolide antibiotic may also be resistant to Gamithromycin. The drug's use is managed according to antimicrobial stewardship policies to minimize this risk.

Q: Is ZACTRAN the first-line treatment for its indication?

Regulatory guidance advises that when possible, an antibiotic with a lower risk of promoting antimicrobial resistance should be chosen for first-line treatment. The use of ZACTRAN is determined by the veterinarian's professional judgment, in alignment with official national and local antimicrobial policies.

Q: Are there any official patient resources or support groups for ZACTRAN users?

Official regulatory labels (such as those from the FDA or EMA) provide contact information for the manufacturer or the government authority (like FDA-VETS). These resources are intended for reporting adverse drug events or seeking technical assistance from the manufacturer.

Q: Can I switch from [Similar Drug] to ZACTRAN easily?

Official documents contraindicate the simultaneous administration of ZACTRAN with other macrolide or lincosamide antibiotics. Therefore, any decision to switch between these similar classes of antimicrobials is a determination made and managed by a licensed veterinarian.

How should ZACTRAN be stored and disposed of?

How to Store and Dispose of ZACTRAN (Gamithromycin) Injection

ZACTRAN must be stored according to regulatory requirements to maintain its stability. The product should be stored at or below 77°F (25°C), with permissible excursions up to 86°F (30°C).

Keep the product in the original outer carton and ensure the container remains tightly closed. The unopened product has a shelf life of 3 years. Once the vial is first punctured, the contents must be used within 28 days (or 18 months, as per the U.S. label for cattle).

Disposal must be conducted in accordance with local requirements for veterinary waste. The product must not contaminate surface water or be thrown into household waste due to the risk posed to the aquatic environment. Store the medicine out of the reach of children.

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