Hi ! Good afternoon. I am Dr Shareef answering your query. Avil is an antihistamine drug used for any kind of allergic reactions, and it is also given as intra-venous injection for having a fast relilve of the symptoms, which might have happen if it is taken orally. As with any anti histaminics, Avil can also cause drowsiness and the intravenous injection must have done it fast which manifested it as your dizzines and even unconsciousness. I hope this should pass off gradually. If it persists, then I would advise you to see your family physician who would advise for further management after seeing you. I hope this information would help you in discussing with your family physician/treating doctor in further management of your problem. Please do not hesitate to ask in case of any further doubts. Thanks for choosing health care magic to clear doubts on your health problems. Wishing you an early recovery. Dr Shareef.