There are many brands and forms of Brudifen http://eridanuspills.com/diabetes-medications/aglumet.php. Diphenhydramine including not FDA approved for use in horses, but it is commonly used and considered acceptable practice. Drinking alcohol can increase certain side effects of diphenhydramine.
Possible side effects of Brudifen include:
Brudifen is used to treat diseases such as: Allergic Reactions, Allergic Rhinitis, Cold Symptoms, Cough, Extrapyramidal Reaction, Insomnia, Motion Sickness, Nausea/Vomiting, Pruritus, Urticaria.
Dosage adjustment not necessary unless patient is hypovolemic. The recommended dose is 100 mg PO twice daily.