I think you should take the dog to a vet if it needs medical attention.

Withania somnifera is in the nightshade family and has alkaloids that might be bad for dogs. Remember that we can eat chocolate and it kills them, so you can't look at human use and think it's OK for dogs.

Actually he is beeing followed for a long time by the veterinarian. He has visceral Leishmania for 2 years and a half. He does lab tests frequently (3-5 times a year). He tried conventional medecine (allopurinol and milteforan) with mild sucess. We are in south Europe where leishmania is farily common in dogs. I dont think withania somnifera is bad for dogs, actually there are a few studies with dogs taking withania for the immune system, specially to address immunocompromised issues, kidney nephrite,.... There isnt any reported bad side effects on those experimental studies, actually on the contrary, inclusive some leishmanicidal effect. Anyway withania is discussed in Barbara Fougere book "Veterinary Herbal Medecine" (2007). Anyway so far he is been taking withania for 1 month (powder form) and his lab tests seem to be normalizing and apperently his immune system seem to be reversing to a more cellular specific response to leishmania. But it is to early to say if it is beeing really efficacious. He also took turmeric (98%) with black pepper (2%), glyccyrrizha glabra, althea officinalis and urtica dioica seed oil extract to try to arrest any kidney damage.

My question is if the powder form is less efficacious than for example an extract?

Thanks

Apart from the issue of toxicity in dogs, there's the problem of herbal supplement standardization to assure consistent dosages, and the known hazard of heavy metal contamination of Ayurvedic medicines (this problem extends to Withania (ashwaganda).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2755247/

Hopefully your vet is aware of what herbs you're trying and can advise on the potential for toxicity and herb-drug interactions.

Indeed you are right, specially today that the demand are enormous. Some are even well known manufacturers. Well its always a risk. I myself take Withania somnifera powder for about 4 years with some intervals. I try to be acertive with where i buy but indeed always a risk in that aspect. Normally i buy at indigo herbs Uk, Biosamara,...
My vet as some minor knowledge about herbs like astragalus, turmeric, artemisia,... but actually not about withania somnifera. Before i started to give my dog withania somnifera (and also other herbs) i searched every publication available about holistic/herbal/homeopathic veterinary medicine to be sure about dosages, possible side effects, LD, formulations, indications, pharmokynetics,etc....

So far i cant find any contraindication for Withania somnifera given to dogs (and also his lab tests show positive results).

But i would be much appreciated if you know any case/cases of toxicity giving withania sominfera to dogs.