Varniclex 1 Tablet 10's is used to treat nicotine addiction. It contains Varenicline, which helps in reducing the craving and withdrawal symptoms that occur after quitting smoking. In some cases, this medicine may cause side effects such as nausea, headache, vomiting, drowsiness, gas, constipation, trouble sleeping or insomnia, unusual dreams, and taste changes. Inform the doctor if you are pregnant or breastfeeding, taking any other medication, or have any pre-existing medical conditions.