SYNTHETIC ACTH (COSYNTROPIN) STIMULATION TESTS IN NORMAL DOGS - COMPARISON OF INTRAVENOUS AND INTRAMUSCULAR ADMINISTRATION

The plasma cortisol and immunoreactive (IR)-ACTH responses to 250 mug synthetic ACTH (cosyntropin) administered by either the intravenous (I V) or intramuscular (IM) routes were compared in 12 healthy dogs. Afte r IV administration, the mean peak plasma IR-ACTH concentration (147 p mol/L; SEM=29.5) was significantly higher (p<0.01) than after IM admin istration (43 pmol/L; SEM=5.5). However, the mean peak cortisol concen tration after administering cosyntropin IV (291 nmol/L; SEM=38) was th e same as the mean peak cortisol after IM administration (280 nmol/L; SEM=39). Therefore, the authors conclude that although higher plasma A CTH concentrations occur following IV injection of cosyntropin, the pl asma cortisol response is identical after IV or IM administration of t his drug.