Not really bitter... it doesn't taste like anything I can describe.
The horse paste is apple flavored, so theres no way to compare that either.
ADC is supposed to be a reputable supplier. You should get sick after your first dose.. that would be an easy way to see how effective it is. Some people get migraines too that dont let up with subsequent doses either. The horse paste is safe and easier and ... plus it can be gotten almost anywhere. Just make sure to read the box and make sure it doesn't have trichlorfon in it. Most ivermectin horse paste shouldnt The fenben horse paste does and it's a pesticide used against flies... not sure how safe it is in humans, but I wouldn't want to give it to my horse either.