Clinical and pharmacokinetic interactions between oral fluconazole and intravenous ketamine and midazolam in dogs.

OBJECTIVE

To evaluate drug interactions between fluconazole and the intravenous (IV) anesthetic induction agents, ketamine and midazolam.

STUDY DESIGN

Randomized parallel study.

ANIMALS

A group of 12 adult healthy Beagle dogs.

METHODS

Dogs were randomly allocated to two groups of six dogs. Dogs in group KM were administered IV ketamine (7 mg kg) and IV midazolam (0.25 mg kg), and dogs in group KMF were administered fluconazole (5 mg kg) orally 12 and 24 hours prior to ketamine-midazolam using the same doses as KM. Sedation scores (0-4) were assigned by investigators unaware of group assignment. Heart rate (HR) and times to sternal and standing were obtained and compared between groups for differences with p < 0.05 considered statistically significant. Blood was obtained and plasma drug concentrations were measured using liquid chromatography-mass spectrometry.

RESULTS

The times to sternal, mean 32.3 and 24.6 minutes, for groups KMF and KM, respectively, were not different between the groups. The time to standing, 73 and 36 minutes in groups KMF and KM, respectively, was significantly different (p = 0.002). The duration of elevated HR compared with baseline was longer in KMF (110 minutes) than in KM (25 minutes) (p < 0.05). In group KMF, one dog developed hyperthermia (40.6 °C), which resolved spontaneously. The clearance of ketamine and midazolam was significantly slower (approximately 50%) and the area under the curves were significantly higher (two-fold) in group KMF (p = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

A significant interaction between oral fluconazole and IV ketamine-midazolam occurred, but the effects appear minor in healthy dogs. Based on these data, a single dose of ketamine-midazolam is not contraindicated in dogs treated with fluconazole, but the duration of effects and pharmacokinetics are altered.