It's crucial to contact a veterinarian immediately.
Here's why:
* Serious underlying conditions: The symptoms you described could be caused by a range of serious conditions, including neurological issues, poisoning, or even a life-threatening illness.
* Time is of the essence: Prompt veterinary care can be crucial to the horse's recovery and survival.
What to do next:
1. Contact your friend and urge them to call their veterinarian immediately.
2. Offer your support. You can help by offering to stay with the horse, keeping it calm, or helping to arrange transportation if necessary.
3. Gather as much information as possible. Ask your friend about any potential causes they're aware of, recent changes in the horse's routine, any other symptoms they've observed, and any medications the horse is taking. This information can be helpful for the veterinarian.
Remember, a veterinarian is the only one qualified to diagnose and treat your friend's horse.