Vitex is said to elevate progesterone levels, I'm not sure about it being anti androgenic, but 600mg doesn't sound too much. I'm taking 1600mg a day as capsules and have zero problems with it. I wonder if the liquid tincutre form is stronger, I have only tried capsules so far. Since I started taking Vitex & EPO combo, my breast development has been quite positive and it feels like its doing some sort of balancing thing, bit similar as what BO does.
So dosage is all good and you could likely easily go even higher without problems. I'm on this combo for five and half months right now and I love it, I need to stock up on both soon as i'm running low. Is this a long time? Six months soon? Zero issues, its one of those nice simple herb things that I've found useful.
25mg Bica per day is a LOT, are you sure you need that much? If you take that much, you probably should lower your dose once it has built up enough. 50mg PER WEEK can be enough once there's decent T suppression going on. I'm switching on Bica hopefully soon, I should get them within about a week or so and I'm planning on waning down Cypro while starting Bica on very small dose. Due to long halflife, 25mg taken biweekly can work. It averages to 7,14mg per day which should be enough at this stage of having T suppressed really well for quite long time.
I don't think there's any issue taking Vitex at the same time.