title: Effects of clarithromycin, azithromycin and rifampicin on terbutaline-induced sweating in foals.
abstract: BACKGROUND
  Erythromycin (ERY) induces anhidrosis in foals. Azithromycin (AZI) and clarithromycin (CLA), often combined with rifampicin (RIF), are commonly used to treat Rhodococcus equi infections, but effects on sweating have not been investigated.
  
  
  OBJECTIVE
  To determine the effects of AZI, CLA and RIF on sweat responses in normal foals.
  
  
  METHODS
  Each experiment was a blinded, duplicated, six foal × three period counterbalanced within subjects design (12 foals/experiment).
  
  
  METHODS
  Antimicrobials were given orally for 5 days. In Experiment 1, ERY, AZI and CLA were given. In Experiment 2, ERY, RIF and ERY/RIF combination were used. Quantitative intradermal terbutaline sweat tests were performed daily for 3 days before and 1, 2, 5, 9, 24, and 39 days after treatment. Data were analysed by repeated measures analysis of variance procedures. Significance was P≤0.05.
  
  
  RESULTS
  In Experiment 1, all macrolides suppressed sweating although CLA and AZI were less potent than ERY. In Experiment 2, significant sweat suppression occurred in foals given ERY with or without RIF, but there was no effect of RIF alone. Rifampicin reduced sweat suppression by ERY on Day 1 of treatment but not thereafter.
  
  
  CONCLUSIONS
  Because ERY blood concentrations were not measured, effects of RIF on ERY-induced anhidrosis could not definitively be ascribed to altered ERY bioavailability.
  
  
  CONCLUSIONS
  All macrolides commonly used to treat R. equi pneumonia, i.e. ERY, AZI and CLA, induce anhidrosis in foals. The potent anti-sudorific effect of ERY is delayed, but not substantially affected by concurrent RIF administration.
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Stieler Stewart
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: L C
authors.initials: LC
authors.lastname: Sanchez
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Mallicote
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Muniz
authors.affiliation: Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands.
authors.forename: M S
authors.initials: MS
authors.lastname: Westerterp
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Burrow
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: MacKAY
mesh_terms: D000818:Animals; D017963:Azithromycin / Q000494:pharmacology*; D017291:Clarithromycin / Q000494:pharmacology*; D006736:Horses; D012293:Rifampin / Q000494:pharmacology*; D013546:Sweating / Q000187:drug effects*; D013726:Terbutaline
chemical_list: D017963:Azithromycin; D017291:Clarithromycin; D013726:Terbutaline; D012293:Rifampin
keywords: 
  Rhodococcus equi
  ; anhidrosis; foal; horse; macrolide; rifampicin