Is this it? If so, they are antibacterial.
Yes birds can get ear infection. Sometimes they shake their heads, or their balance can be affected. You may also smell an off odour and notice waxy build up or even pus. It can be quite nasty for them. I wouldn't say that it is common, but it does happen. How did the vet diagnose the problem?
Is there any reason why the bird is susceptible to this at the moment? Perhaps you should think about whether the birds have been wormed, if they are on an appropriate diet. Also keep a close eye on your flock for any signs of respiratory infection such as head shaking, mucous from nostrils, eyes or mouth, or anything else at all. It is probably an isolated problem, but it's always a good idea to observe your birds carefully.