GENERAL GUILDELINES FOR ACTH RESPONSE TESTING
1. Monitoring Lysodren therapy: ACTH stimulation testing is recommended after the initial induction period (7-10 d of daily Lysodren). If additional induction phases are required, an ACTH stimulation should be done at the end of each phase. Once the dog is on maintenance, an ACTH stimulation should be done 3 months and 6 months later. Periodic retests at 6 month intervals are recommended, if the patient is responding well to treatment (earlier if not).
2. Monitoring ketoconazole therapy: The initial dose of ketoconazole is 5 mg/kg bid for 7 days. If there are no adverse effects, the dose is increased to 10 mg/kg bid and an ACTH stimulation should be done after 14 days. If cortisol levels are not within the ideal range, the dose should be increased to 15 mg/kg and an ACTH stimulation again done after 14 additional days. The ACTH stimulation test should begin within 1-3 hours of the last dose of ketoconazole.
3. "Ideal" values: in a Cushings dog receiving either Lysodren or ketoconazole are pre-ACTH cortisol, 30-100 nmol/L and post-ACTH cortisol, 30-110 nmol/L. In other words, we like to see measurable cortisol levels which do not rise above 110 nmol/L after ACTH.
Interpretation of specific results with the ACTH stimulation test during therapy with Lysodren
At completion of induction therapy (daily loading therapy):
1. If both cortisols (pre and post ACTH) are between 30 and 110 nmol/L, go to maintenance therapy.
2. If both cortisols (pre and post ACTH) are above 110 nmol/L, continue daily Lysodren and repeat ACTH stimulation in 5 days. Continue daily therapy until cortisols are between 30 and 110 nmol/L.
3. If both cortisols (pre and post ACTH) are below 30 nmol/L, stop Lysodren, wait 3 weeks, retest with ACTH stimulation and start maintenance when cortisols increase into 30-110 nmol/L range. Dog may require glucocorticoid supplementation, especially if stressed. Also, monitor Na/K to see if Addisons is present.
During maintenance therapy:
1. If both cortisols (pre and post ACTH) are between 30 and 110 nmol/L, continue as is.
2. If both cortisols (pre and post ACTH) are below 30 nmol/L, stop Lysodren, retest with ACTH stimulation at 3-4 week intervals until cortisols increase into 30-110 nmol/L range, then resume maintenance. Dog may require glucocorticoid supplementation, especially if stressed. Also, monitor Na/K to see if Addisons is present.
3. If both cortisols (pre and post ACTH) are well above 110 nmol/L, re-initiate loading Lysodren at 50 mg/kg on a daily basis for 5 days. Retest with ACTH stimulation after 5 days to see if cortisols have dropped, and continue daily Lysodren until they do. Once cortisols are between 30 and 110 nmol/L, restart weekly maintenance at a dose 50% above that used previously.
4. If both cortisols (pre and post ACTH) are slightly above 110 nmol/L, increase weekly Lysodren dose by 25% and retest with ACTH stimulation in 4-6 weeks.
ACTH Response (stimulation) testing for monitoring Cushing's therapy
