Acid reflux medication lansoprazole dapoxetine belongs to a class of selective serotonin reuptake inhibitors (SSRIs). This short-acting inhibitor is used to treat premature ejaculation in men. Many people using this medicine do not have serious side effects. If you think you have used too much of this medicine seek emergency medical attention right away. The symptoms of overdose usually include chest pain, nausea, irregular heartbeat, and feeling light-headed or fainting.