The world of pharmaceuticals may have faced a patent cliff in recent years, but brand name drugs are still generating billions upon billions in annual sales in the United States alone. Some of these so-called blockbuster drugs are even generating more than $1 billion each and every quarter in the United States. These drugs treat depression, arthritis, acid reflux, high cholesterol, chronic obstructive pulmonary disease and more. After tallying the top seven drugs alone, the U.S. sales are more than $9.1 billion per quarter.

A new list compiled by Drugs.com for the first quarter of 2013 shows that all but one of the seven drugs with $1 billion in quarterly sales saw total sales gains. Only three of the wider list of the top 20 drugs in quarterly sales posted negative sales trends. You will notice that many of the drugs had negative unit (prescriptions) trends again in the first quarter, but this was seen by and large a year ago as well.

We used data from Drugs.com, and this represents the top-selling drugs and medicines measured as U.S. national sales through both retail and hospital channels. This list is for the first quarter of 2013, and we have provided an image of the top drug sales on a chart below.

Abilify by Otsuka Pharmaceutical Co. led the list, at $1.526 billion in quarterly sales with a 3.24% gain. What is interesting here is that the number of units sold in the quarter was shown to be down by 5.89% to 2.477 million units sold, despite a continual rise in total sales. This will seem sad to be the list leader to many people, because Abilify is prescribed as an add-on drug treatment for adults with unresolved symptoms of depression after at least six weeks on an antidepressant. It is also meant to be taken in addition to an antidepressant rather than as a standalone drug.

Nexium by AstraZeneca PLC (NYSE: AZN) was second on the list, at $1.458 billion in quarterly sales with a 1.21% gain. After a small uptick in dollars sold, there was actually a small drop of 2.47% in units to 6.667 million units in the quarter. Nexium is known as the Purple Pill to treat heartburn caused by acid reflux.

Cymbalta by Eli Lilly & Co. (NYSE: LLY) came in third on the list, with $1.296 billion in quarterly sales after a 5.65% gain. Cymbalta units fell by 2.09% to 6.502 million units. Cymbalya is meant to treat major depressive disorder (MDD), generalized anxiety disorder (GAD), for the management of diabetic peripheral neuropathic pain and fibromyalgia, and to manage chronic musculoskeletal pain due to chronic osteoarthritis pain and chronic low back pain.

Crestor by AstraZeneca PLC (NYSE: AZN) was fourth, with quarterly sales of $1.295 billion after a 1.59% gain. Unit sales were down by 2.93% to 4.106 million units in the first quarter. Crestor is prescribed (along with diet) to lower high cholesterol and to slow the buildup of plaque in arteries.

Advair Diskus by GlaxoSmithKline PLC (NYSE: GSK) came in at number five, at $1.277 billion in sales after a 6% rise. This was the first of the list with a per unit gain, with sales up 1.81% to 5.959 million units. Advair Diskus is for the treatment of asthma in patients four years and older. It is approved for adults with chronic obstructive pulmonary disease (COPD), including chronic bronchitis, emphysema or both.

Humira by Abbott Laboratories (NYSE: ABT) was ranked number six, with $1.217 billion in quarterly sales after a 0.91% gain. This drug’s unit sales were down by 5.68% to 631,000 units in the first quarter. Humira is prescribed for moderate to severe rheumatoid arthritis, moderate to severe chronic plaque psoriasis, moderate to severe Crohn’s disease, moderate to severe ulcerative colitis, ankylosing spondylitis, psoriatic arthritis and in moderate to severe polyarticular juvenile idiopathic arthritis.

Enbrel by Amgen Inc. (NASDAQ: AMGN) was the last of the top seven drugs with sales of more than $1 billion, at $1.075 billion in quarterly revenue. This was also the sole drug on the list that had a decline in total dollar sales, with a 1.22% drop. Enbrel even led the top drugs here on this list with a 6.83% decline to 969,000 units sold. Enbrel is indicated for moderate to severe plaque psoriasis, psoriatic arthritis and moderate to severe rheumatoid arthritis.

You probably noticed that there was a steady decline in unit sales in the first quarter. In most cases, this was also the case in the first quarter of 2012. It seems that the trend can be influenced by timing as well as by rotational use or by the public’s routine annual changes, more so than drug companies arbitrarily raising their prices each year to make up for lower unit sales.

We also have two runner-ups here that are close to $1 billion in quarterly sales. Remicade from Johnson & Johnson (NYSE: JNJ), under the old Centocor and Janssen unit, posted a 3.58% sales gain to $969 million. Copaxone from Teva Pharmaceutical Industries Ltd. (NYSE: TEVA) posted a 1.98% sales gain to $926 million.

Read also: Viagra to Be Sold Online Soon

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