I would like to add Brefeldin A 1 to 2 hours after the stimulation has begun, but DURActive 1 already contains Brefeldin A. Or I might want to add monensin instead, or to work without any secretion inhibitor. What are my options?

You can use DURActive 2, which contains the same PMA/Ionomycin mixture as DURActive 1 but without Brefeldin A