Prophylaxis means prevention . . . I do not believe any dentist or doctor in their right minds would prescribe an antibiotic to protect your teeth against a potential future infection.
Medications affect different individuals in different ways. A pharmacist would be a reliable source of information on the side effects of any specific medication.
There are many different kinds of antibiotics that contain different substances. In simple terms, an antibiotic is a medical substance derived from chemical preparations, organic preparations, etc....
Some of them are the same medicines, but the dosage is VERY different for animals than for humans. Cats and dogs and other small pets cannot take the large doses of medicines that humans can take....