US health insurers should use both medical and pharmacy data to forecast specialty drug costs, which are predicted to rise to account for 50% of total US commercially-insured drug costs by 2018, according to a new study.

Specialty drugs require special handling, are typically injected and are more expensive that traditional drugs. In 2009 they accounted for 20% of US medical and pharmacy benefit drug costs, and by September 2012 their share had increased to 28.7% of the total, says the study, from pharmacy benefit manager (PBM) Prime Therapeutics.

The increasing rate of specialty drug expenses is due to increased non-specialty generic drug use, expected continued annual double-digit price rises from pharmaceutical manufacturers, growing usage of specialty drugs and the future pipeline for such treatments, said Patrick Gleason, director of health outcomes at Prime, which presented the findings of its study at the Academy of Managed Care Pharmacy (AMCP)'s annual meeting in San Diego.

"Specialty drugs offer life-saving treatments for patients, but they also come with a high price tag. In the years ahead, health insurers and plan sponsors will need to increase their focus on managing specialty drugs to ensure the most cost-effective outcomes for their members," said Dr Gleason, and he advised insurers to focus on four management opportunities - drug distribution channels, utilisation management, contracting activities and coordination of care.

While specialty drugs have historically been associated with rare medical conditions, they are being used more frequently for the treatment of more common chronic conditions such as rheumatoid arthritis (RA), the firm notes. Two new studies from Prime, conducted in conjunction with Blue Cross and Blue Shield of Minnesota and also presented at the AMCP meeting, show that such treatments for RA and hepatitis C already make up more that half the total cost of care for US patients with these two conditions.

The first study found that while the overall use of hepatitis C specialty drugs had dropped from 17.2% in 2008 to 14.1% in 2011, the compound annual growth rate (CAGR) for pharmacy cost of care fr the condition was 15% during the period. Specialty drug costs accounted for 35% of the total cost of hepatitis C care in 2008 but had soared to 52.6% by 2011, with a CAGR of 31.8%.

The second study reported that use of RA drugs remained steady from 2008 to 2010, at 34.6% versus 35.4% respectively for the two years, but that the CAGR for total cost of care was 7.3% during the period, while the CAGR for all other medical costs was 10.4%. Combined RA medical and specialty drug costs accounted for 54.7% of total cost of care in 2008, dropping slightly to 53% by 2010, with a CAGR of 5.6%, say the researchers.

These studies show that RA and hepatitis C pharmacy costs now go beyond all medical costs - "therefore, the expected medical savings cannot offset the specialty drug investment," commented Dr Gleason.