Double Compression

• Double compression, also known as direct compression, involves weighing a drug, then crushing it into a fine powder. This is mixed with other ingredients known as excipients. This mixture is compressed into tablets, which are initially fragile. A different part of the tablet machine then compresses these fragile tablets into a hardened form suitable for packaging.
  
  

Excipients

• To be effective, tablets need to dissolve.Jupiterimages/Photos.com/Getty Images
  
  Sometimes an excipient is applied during the second compression. Excipients can include disintegrates to help the pill break down enough to be absorbed; lubricants to help the tablet make it down to the stomach; surfactants, which increase solubility, and absorbents to aid in delivering medicine to the host.
  
  

Compression Machines

• Compression machines, including those capable of double compression, are complex, expensive mechanisms. They can weigh three tons, and some can produce as much as 45,000 pills an hour.