When starting this medication, it certainly takes up to two weeks to start getting used to the dosage and up to 4 weeks to see the benefits of the medication in effect. At first, a person might go through some mild side effects such as nausea, sleepiness, weakness, dizziness, anxiety, trouble sleeping, sweating, and sexual problems, amongst others. But they should subside within two weeks. If it still doesn't, then the medication probably isn't suited to you and in such case, letting your doctor know about it is the best so they can change the dosage or the medication altogether.