The Food and Drug Administration on Tuesday approved the first in a new class of drugs that blocks the nerve channels responsible for transmitting pain signals. It will be marketed as Prialt and should be available by the end of January.
"When you've taken all the kinds of pain medication that there is and you still have pain, that is a very frightening situation," said Dr. Lars Ekman, president of research and development for the drug's Ireland-based manufacturer, Elan. "When you have that kind of pain, there is nowhere to go."
The drug is part of a new class known as N-type calcium channel blockers. It is known chemically as ziconotide.
Morphine is standard treatment for severe pain from cancer, AIDS, amputations and other significant illnesses, but its effects eventually wear off and the dosage must be increased. At some point, many patients switch from taking medication by mouth or by injection to a microinfusion pump implanted under the skin that delivers drugs directly into the fluid surrounding the spinal cord.
Ekman said 35,000 to 50,000 Americans have these pumps now. The FDA approved Prialt for patients who are already using these pumps but not getting effective relief from them or who cannot tolerate the available treatments.
This is the first new drug in 20 years to treat pain using such a pump.
Prialt has been studied in patients with cancer, AIDS and other chronic pain, such as back pain. More than 1,200 patients took part in three clinical trials.
There are side effects, and the FDA was including a "black box" warning — the government's strongest warning short of a ban. Side effects may include dizziness, drowsiness and altered mental status, with patients confused at times.
Despite the side effects, the drug was approved because there are no other options for these patients and the benefits outweighed the risks, said Dr. Robert Meyer, director of the FDA's Office of Drug Evaluation II.
"Because this is such an important patient population where they have such pain and they have so few options, we felt this drug does offer some real gains," he said.
Patients with a history of psychoses should not receive it, and all others should be monitored for signs of cognitive impairment, he said.
The idea for the drug came from a snail called the Conus magus that lives in the South Pacific, which paralyzes its victims with venom after capturing them, the company said. Researchers set out to learn how to develop a drug based on this venom and eventually copied the amino acid sequence.
Elan would not say how much it plans to charge for the drug.