Use Caution Mixing Chastetree Berries With Pergolide
Chastetree berries (CTB), aka Chasteberry, aka Vitex agnus-castus is an herbal remedy I first published about using in horses with PPID (Cushing’s) back in 2000. It had been determined that CTB could help normalize prolactin levels by binding to dopamine receptors in the brain. Low dopamine activity is at the root of PPID so I decided to try it.
Vitex flowers and berries
The initial trial was an observational study. All horses were correctly diagnosed but follow up blood work was not standardized. Emphasis was on signs/symptoms. Response was very positive, especially with coat and foot comfort, but even in this short preliminary study I noted it may not be appropriate for advanced cases, and of course a lot more work needed to be done. There was also concern about how it might interact with pergolide since both act by binding to dopamine receptors.
Since then, a study out of New Bolton found no benefit but used advanced cases and graduated doses of pergolide compared to a set dose of CTB. The Laminitis Trust in the UK studied horses for at least a year on CTB and contradicted the findings of that study. They confirmed obvious benefits with symptomatology but no consistent effect on hormone levels like ACTH.
The latest study looked at confirmed PPID horses on CTB alone, CTB plus pergolide or pergolide alone. Horses on both had better resolution of the abnormal PPID coat but horses on CTB alone or CTB + pergolide had much higher ACTH levels than pergolide alone, indicating CTB can likely interfere with the effects of pergolide. The effect was particularly obvious when the seasonal ACTH rise was approaching.
Pergolide is the gold standard treatment for PPID/Cushing’s and can control the abnormal hormone output from the pituitary. CTB has never been documented to do that, and now it appears it may actually interfere with pergolide effects. This is not surprising since it is competing with the drug for binding sites on dopamine receptors but its effect when bound is apparently not as strong.
The bottom line here is that CTB alone is not an adequate treatment for PPID. Symptoms may improve for a while but the abnormal growth in the pituitary goes unchecked and when CTB stops working the process is much more difficult to get under control. I’ve seen that happen. This new research also shows you must be careful in combining it with pergolide because the CTB may block the drug’s effects.
Eleanor Kellon, VMD
Dr. K's Horse Sense 
Lets not condemn Chaste Berry just because it might have a problem with the Rx Ps. It can do a lot of good without them and at a starting price difference of 22 cents a day to $2 a day; worth considering for those of us who wold find it impossible to keep a horse at those added costs.
My 19 yo gelding (who had all the Cushings signs) has been on “Remission” and 1600 mg Vitex for 6 years. His hard cresty neck is long gone, his weight is good, he sheds beautifully, he is trimmed properly every 4 weeks and has never been lame, He is on year round turnout, with new grass access made gradually. And he gets (500-1000) miles a year of regular exercise, ridden and driven, barefoot sound.
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This wasn’t a condemnation of CTB. It was a warning specifically about combining it with pergolide. At 13 YO, it’s highly unlikely your horse had PPD/Cushing’s. You are describing signs of EMS/IR, not PPID. The exercise is most likely to be doing the most good.
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Many thanks for your advice. Will discuss getting blood work done with my
vet and the possibility of cystic follicles. Could you clarify if this follicle issue would still occcur despite the Improvac injections? And could their presence actually cause the high insulin levels and laminitis? .Thank you.
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Hi Dr Kellon. I have a 20 year old Haflinger mare. She is IR/EMS/PPID.
She also suffers from seasonal transitional laminitis which we have controlled for the last three years with two Improvac (UK version of Equity) Iinjections in Spring and a top up in Autumn.
She is on Prascend. Last year dose increased to 2 tablets a day after regular annual TRH stim. This dosage has been highly effective coat shedding normal and cessation of PU/PD.
On the advice of a nutritionist I started to supplement her diet begiinning start of April with a chasteberry blend NAF Cushinaze to help get rid of abnormal fat pads. She quickly developed a huge crest despite following all laminitic protocols re diet and crashed down with acute laminitis four weeks ago. She is on box rest in Imprint Shoes and on Levo-Thyroxine to promote weight/crest loss.
Stopped chasteberry last week after havng suspicions. Would you recommend an increase in the Prascend dosage? Willl contact my own vet as soon as they open and also ask them to speak to Liphook. Can’t believe I only joined this site last night…..although I have followed you for many years.
Janette Carter
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I would probably want blood work before increasing the dose. Also make sure she has no access to grass or other young vegetation and if you haven’t seen her cycling yet get a rectal exam or ultrasound. The Spring transition often has waves of follicles which fail to ovulate or even can become cystic. Mares with IR/PPID can develop persistent cystic follicles that are associated with laminitis and high insulin.
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Hi Dr. Kellon, Pabatsa turns 24 tomorrow. I had him tested last week: his Cornell numbers were good with ACTH at 21. I/G were low. He’s in dressage work and being shown at rated shows with high scores!
I have had P on SUPER’s liquid CTB for many years. After reading this, I’m now concerned about it interfering with his 4.5 mg CP. Should I take him off the CTB and if so does he need to be weaned off of it?
Thank you, Laura
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Since his ACTH is normal you are obviously giving enough pergolide to counteract any interference. You may or may not need less pergolide if you stop it but the seasonal rise is beginning soon so I wouldn’t try lowering it now. No need to wean.
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Could CTB be helpful in preventing PPID in horses whose breeding/type might make them more likely to develop it?
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Metabolic Syndrome/IR risk is higher in certain breeds but all horses are at risk for Cushing’s. CTB won’t prevent it.
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