Firstly, take only Isoprinosine AS ADVISED by the doctor. Comply with the regimen given and do not attempt to extend the duration of the treatment and the dosage. Isoprinosine has anti-viral properties. Over-using it will make you immune to the drug. It will break its purpose of making you immune to virus. If it can't work to protect or boost your immune system, then you will have to take a drug that is more potent than Isoprinosine.
Secondly, although your throat appears and feels okay after 5 days of treatment or even when the infection is already treated, smoking can cause further irritation of the throat. Smoking damages the linings of the throat, thus, making you a candidate (again) for throat infection.
I hope I was able to enlighten you.