Comparison of pharmacodynamic variables following oral versus transdermal administration of atenolol to healthy cats.
OBJECTIVE
To describe the disposition of and pharmacodynamic response to atenolol when administered as a novel transdermal gel formulation to healthy cats.


METHODS
7 healthy neutered male client-owned cats.


METHODS
Atenolol was administered either orally as a quarter of a 25-mg tablet or as an equal dose by transdermal gel. Following 1 week of treatment, an ECG and blood pressure measurements were performed and blood samples were collected for determination of plasma atenolol concentration at 2 and 12 hours after administration.


RESULTS
2 hours after oral administration, 6 of 7 cats reached therapeutic plasma atenolol concentrations with a mean peak concentration of 579 +/- 212 ng/mL. Two hours following transdermal administration, only 2 of 7 cats reached therapeutic plasma atenolol concentrations with a mean peak concentration of 177 +/- 123 ng/mL. The difference in concentration between treatments was significant. Trough plasma atenolol concentrations of 258 +/- 142 ng/mL and 62.4 +/- 17 ng/mL were achieved 12 hours after oral and transdermal administration, respectively. A negative correlation was found between heart rate and plasma atenolol concentration.


CONCLUSIONS
Oral administration of atenolol at a median dose of 1.1 mg/kg every 12 hours (range, 0.8 to 1.5 mg/kg) in cats induced effective plasma concentrations at 2 hours after treatment in most cats. Transdermal administration provided lower and inconsistent plasma atenolol concentrations. Further studies are needed to find an effective formulation and dosing scheme for transdermal administration of atenolol.
Macgregor
John M
JM
Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA.
Rush
John E
JE
Rozanski
Elizabeth A
EA
Boothe
Dawn M
DM
Belmonte
Albert A
AA
Freeman
Lisa M
LM
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D001262:Atenolol / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D002415:Cats; D006262:Health; D008297:Male
D000959:Antihypertensive Agents; D001262:Atenolol