With almost 70% of the population taking at least one prescription drug, and 20% take at least five, there is no doubt that America is still a prescription nation.

The statistics above mentioned has been on a consistent increase since 2005, according to the Mayo Clinic and Olmsted Medical Center research.

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Health issues aside, the country's dependence on prescription medication has left a huge impact on the economy, as reported by TIME. IMS Health Informatics reported that people in the US spent almost $374 billion on the said drugs for the year 2014.

Here are the five top-selling drugs that greatly contributed to the increase of sales in the pharmaceutical industry last year, along with the cost of each medication when taken within a month.

Top 5 Crestor, $5.8 billion

Crestor is prescribed to combat high cholesterol and address triglyceride levels, which could also reduce the risk of heart diseases. A month's worth of medication of Crestor costs from $219 to $225.

Top 4 Nexium, $5.9 billion

Mainly for treating frequent acid reflux and stomach ulcers, Nexum is also approved for gastroesophageal reflux disorder (GERD) and injured esophagus. Its monthly cost would be around $252 to $273. However, last January, a new generic brand for this drug called esomeprazole, which costs only $103 to $199.

Top 3 Humira, $7.2 billion

Originating from animal cells or tissues, Humira is a biologic drug that can address eight conditions. Among the diseases include plaque psoriasis, Crohn's disease, and various kinds of arthritis. While its monthly dosage costs $3,305 to $3,408, patients prescribed with this medication need to take a larger dose before they can do the monthly maintenance.

Top 2 Abilify, $7.8 billion

Abilify is meant for psychiatric disorders, such as schizophrenia, depression, and bipolar disorder. This antipsychotic is also allowed to treat irritability correlated to autism. And its monthly dosage cost? $921 to $954.

However, its market is starting to become steep as a generic brand was released called aripiprazole. This alternative is definitely more affordable with only a month-long expense of approximately $371 to $682.

Top 1 Sovaldi, $7.9 billion

Since 2014, Sovaldi is already a top-seller for being prescribed for most types of hepatitis C. This drug can cure 4 out of 6 genotypes of hepatitis C within 1 to two treatment courses. Manufactured by Gilead, it is said to have an impressive 84% to 96% cure rate.

Its seemingly miraculous treatment, however, comes with a steep price of $30,700 to $31,900 per month. Unfortunately, researchers noted that Medicaid does not fully cover for Sovaldi.

TagsDrugs, Sovaldi, hepatitis, Hepatitis C, Medication, Medicaid