Hi Rupali,
It depends which method you want to follow. Like I said Desferal is an injection; (ideally) given slowly by infusion pump in the sub-cutaneous (sub-Q) layer under the skin but it can also be given via the I.V drip. However, the slow sub-Q infusion is more efficient.
Kelfer and Exjade are the oral tablets.
Therefore, the oral tablets are more compliant and preferred if you want to avoid pain.
Chelation is life long until there is a permanent treatment of blood transfusion because it is the chelation that removes the excess Iron that comes with the blood.
As for the side effects, every drug has some in some cases. It is not necessary that everyone will have to face the side effects. Most of the time it is just a mild one and can be cured by lowering the dose. You should not be worried about them
I will list the rare serious ones just for your knowledge but remember it is not necessary that they will happen to everyone.
Desferal is known to effect visual and audio senses if given in large doses in rare cases.
Kelfer is known to decrease the levels of zinc, white blood cells and platelet in some cases so they are monitored with it's use.
Exjade causes temporary mild rash and upset stomach in some people and increases Serum Creatinine in patients with renal issues.
Again, these are very rare and are listed just in case if there is an allergy issues with them for some patient. Even common pain killers have side effects mentioned so these are not to be alarmed about.