Drano is a acid, and it does more harm then good, especially when used in older houses, and in kitchen sinks that have garbage disposals installed.
Most older homes have cast iron drain piping running through the house. Over time the acid eats up the piping causing the lines to get corroded from the inside out and disintegrate. This will cause the pipe to start to leak slowly inside walls, crawl spaces, and under ground. I have come across cast iron piping that the bottom is completely gone.
For garbage disposals it does the same thing. Even if the disposal is completely new if Drano sits in the sink it will eat the inside of the garbage disposal in no time at all.
We at YARO Plumbing recommend a natural bacteria, or an enzyme to help dissolve a drain clog.
If that doesn't work, contact a local plumbing professional. Our drain cleaning technicians know what the best way to open a drain without causing any damage to your lines or plumbing fixtures. YARO Plumbing will clear any drain clog no matter what, if we can't unclog your drain we wont charge you.