Generic drugs made up 78% of all prescriptions dispensed in the US last year, a 4% increase from 2009, a report by the IMS Institute for Healthcare Informatics has shown.

The report revealed that hydrocodone/acetaminophen, a generic pain reliever, was the most popular drug in 2010, with 131.2 million dispensed prescriptions last year.

This was followed by simvastatin, used to lower cholesterol, and lisinopril, a treatment for hypertension.

The only branded-drugs on the list were Pfizer’s Lipitor, Sanofi-Aventis and Bristol-Myers Squibb‘s Plavix, and Merck’s Singulair, which ranked 12, 23 and 25 respectively on the report’s most-prescribed list.

Branded-drugs however, made up the entire list of best-sellers, with Lipitor at number one, generating $7.2 million last year.

Oncologics led all therapeutic classes in spending, generating $22.3bn in 2010, while liquid regulators were the most prescribed, closely followed by antidepressants.