Assessment of serum concentrations and sedative effects of fentanyl after transdermal administration at three dosages in healthy llamas.
OBJECTIVE
To determine the serum concentrations and sedative effects of fentanyl after transdermal administration at 3 dosages in llamas.


METHODS
9 healthy adult female llamas (mean age, 8 +/- 3 years; mean weight, 150 +/- 18 kg).


METHODS
Llamas were allocated to 1 of 3 groups (3 llamas/group). Fentanyl patches (each providing transdermal delivery of 75 microg of fentanyl/h) were placed on shaved areas of the antebrachium of all llamas. In group 1, llamas were treated with 1 patch (anticipated fentanyl dosage, 75 microg/h). In group 2, llamas were treated with 2 patches (anticipated fentanyl dosage, 150 microg/h). In group 3, llamas were treated with 4 patches (anticipated fentanyl dosage, 300 microg/h). For each llama, the degree of sedation was assessed by use of a subjective scoring system and a blood sample was collected for determination of serum fentanyl concentration at 12, 24, 36, 48, 60, and 72 hours after patch placement.


RESULTS
Following the placement of 4 patches, mean +/- SD serum fentanyl concentration in group 3 llamas reached 0.3 +/- 0.08 ng/mL within 12 hours. This concentration was sustained for 72 hours. In group 2, application of 2 patches provided inconsistent results; in group 1, application of 1 patch rarely provided measurable serum fentanyl concentrations. No llamas became sedated at any time.


CONCLUSIONS
Results suggest that application of four 75 microg/h fentanyl patches provides consistent, sustained serum fentanyl concentrations without sedation in llamas. However, the serum concentration of fentanyl that provides analgesia in llamas is not known.
Grubb
Tamara L
TL
Riverview Animal Clinic, 2002 L Schultheis Rd, Uniontown, WA 99179, USA.
Gold
Jenifer R
JR
Schlipf
John W
JW
Craig
A Morrie
AM
Walker
Karen C
KC
Riebold
Thomas W
TW
D000279:Administration, Cutaneous; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000097:blood*; D000818:Animals; D002161:Camelids, New World / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage* / Q000097:blood*; D013997:Time Factors
D000701:Analgesics, Opioid; D005283:Fentanyl