I was taking Guaifenex for blocked Eustachian tubes. I couldn't sleep at night and felt depressed and very nervous on it. Started getting tingling in my head, weakness in my left arm and leg. I stopped taking after 10 days. The tingling and weakness still have not gone away. I'm sleeping much better not being on the drug. It did help clear my ears up though. The side effects were definitely not worth it.