Azithromycin 50 mg/mL + Rifampin 20 mg/mL, Oral Paste, 60mL Syringe
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- Brand
- Mixlab
- SKU:
- NC-0180
- Product Type:
- Paste
- Size:
- 60ml
- Administration:
- Oral
Rhodococcus equi, a gram-positive facultative intracellular pathogen, is one of the most important causes of disease in foals between 3 weeks and 5 months of age. R. equi has also emerged as a significant opportunistic pathogen in immunosuppressed humans, especially those infected with the human immunodeficiency virus (AIDS).1 Infection in both species is most commonly characterized by life-threatening pyogranulomatous pneumonia. R. equi is a soil organism, the growth of which is increased by herbivore manure. It can cause infection in wide variety of mammals, often following immunosuppression.
Disease due to R. equi is rare in adult horses. In adult horses however, it can manifest as an illness similar to that in foals, involving the lungs or the colon and related lymph nodes, or, rarely, as a uterine or wound infection.1 Acquired immunodeficiency of unknown cause in adult horses complicated by R. equi septicemia with lung abscessation has been reported, as well as chronic pyogranulomatous lymphadenitis and enteritis caused by R. equi.2
Medications Effective Against R. equi
A wide variety of antimicrobial agents are active against R. equi in vitro.2 However, because R. equi is a facultative intracellular pathogen that can survive and replicate in macrophages, many of these drugs are ineffective in vivo. In one study, all foals with R. equi pneumonia treated with the combination of penicillin and gentamicin died despite the fact that all isolates were sensitive to gentamicin.3
Although combined therapy with erythromycin and rifampin has dramatically improved the survival rate of foals infected with R. equi, this treatment regimen is not without drawbacks. Erythromycin has variable absorption rates in foals when given orally and requires multiple daily dosing, and its administration has a high incidence of potentially fatal side effects.
Azithromycin and clarithromycin have become widely-applied alternatives to erythromycin for the treatment of R. equi infections in foals in recent years. These medications are more chemically stable, have a greater bioavailability, and achieve higher concentrations in phagocytic cells and tissues than erythromycin. Because R. equi is often isolated in combination with other bacterial pathogens and the identity of the causative microorganism(s) is often unknown when antimicrobial therapy is initiated, in vitro susceptibility data against other common bacterial pathogens of the equine respiratory tract are essential for proper clinical management.2
Azithromycin + Rifampin for Horses
Azithromycin now most often replaces erythromycin in combination with rifampin for the treatment of R. equi in foals. Azithromycin has some anti-inflammatory and immunomodulatory effects, but the clinical relevance of these effects in veterinary species is unknown. Azithromycin has GI promotility properties in humans and has been used as a prokinetic in dogs and cats.4
The combination of a macrolide antibiotic (such as azithromycin) and rifampin is synergistic both in vitro and in vivo, and the use of the two classes of drugs in combination reduces the likelihood of R. equi resistance to either drug.3 Rifampin and macrolides are lipid soluble, allowing them to penetrate cell membranes and caseous material.3,4
Where to buy Azithromycin + Rifampin
Azithromycin + Rifampin is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies.
Azithromycin carries numerous potential drug interactions. Please consult your veterinarian prior to beginning any treatment regimen.
FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.
1Arlotti, M., et. al. (1996) Rhodococcus equi infection in HIV-positive subjects: a retrospective analysis of 24 cases. Scand. J. Infect. Dis.28:463-467.
2Giguere S, Prescott JF. Clinical manifestations, diagnosis, treatment, and prevention of Rhodococcus equi infections in foals. Vet Microbiol 1997;56:313–34.
3Prescott JF. Rhodococcus equi: an animal and human pathogen. Clin Microbiol Rev 1991;4:20–34.
4Hondalus MK. Pathogenesis and virulence of Rhodococcus equi. Vet Microbiol 1997;56:257–268.