Zoloft is the brand name for sertraline HCl and when taken in the recommended dosage is an effective treatment for Levitra versus viagra depression, excessive anxiety and obsessive compulsive disorder. Zoloft's exact mode of action on these affilictions is still not completely understood, however what researchers have seen is that serotonin levels are effectively altered by this drug to reduce symptoms. Serotonin (also known as 5-HT) is part of a drug class know as selective serotonin reuptake inhibitors or SSRI's. This means that rather than blocking the receptors like many other antidepressants they actually inhibit their breakdown.