Ketamine, a drug that is used as an anesthetic, may be a way to safely treat pain, PTSD, depression, and ringing ears (tinnitus), a new study suggests. Since the drug is already approved by the Food and Drug Administration, it could potentially be available sooner and cost less.
“It’s a lot more economical to repurpose drugs than to take a new drug and make it from scratch,” says David E. Potter, professor and chair of pharmaceutical sciences at Texas A&M University’s Rangel College of Pharmacy. “Not only in terms of dollars, but also in terms of time.” And because a treatment is less costly to develop, it should also be more affordable for the patient.
“We need to have science catch up and make sure that it is safe.”
Although it has been used as a fast-acting anesthesia in clinical settings for the last five decades, ketamine’s mind-altering side effects at higher doses, including hallucinations and the feeling of floating, make it a popular street drug.
But researchers are now interested in using it to treat pain, depression, and tinnitus—and they believe that it can be safe and effective at the correct doses.
“We’re doing this principally for pain, but when people have chronic pain, they also commonly develop varying degrees of depression,” Potter says. “Ketamine treats two diseases with one drug.”
It may also be helpful for post-traumatic stress disorder (PTSD) and has been shown to be helpful for tinnitus. “It seems the more severe the tinnitus, the better it works,” Potter says, “because many of the same problems—pain and phantom noises—can predispose to depression and PTSD.”
No approved drug currently exists on the market for tinnitus, so it’s an unmet need, Potter says. “The group that suffers from tinnitus the most is soldiers out on the battlefield. We hope that ketamine will relieve pain, depression and—if they suffer from it—tinnitus as well.”
Although there are numerous existing drugs for treating pain and depression, they’re not adequate in all cases. Antidepressants can be slow to work, if they work for a patient at all. Pain relievers tend to be effective, but morphine can actually make a spinal cord injury worse, and all opioids carry the risk of dependency.
Ketamine acts quickly. Instead of the two or more weeks of a standard antidepressant, such as Prozac, Zoloft, or Effexor, ketamine acts within minutes to hours—which is vitally important in preventing suicide, especially as a single dose of the drug can significantly reduce suicidal thoughts.
It can also help prevent opioid addiction. “Ketamine will prevent the sensitivity to pain that opioids produce when used chronically,” Potter says. “If you give this drug prior to surgery, it will actually lower the amount of opioids required to control pain after surgery, which helps lower the risk of opioid dependence, addiction and adverse effects.”
But ketamine has downsides: it essentially disassociates parts of the brain from each other, which is what leads to the feeling of floating at high enough doses. “The hope is that the doses that are used for appropriate purposes will be low enough to not cause these effects,” Potter says.
It is also still unclear whether there might be unintended side effects in certain populations, such as those with traumatic injuries. “If they want to use ketamine in the battlefield—and the battlefield is a spinal cord injury-laden environment—we really want to make sure that it’s not going to kill cells and impede recovery,” says assistant professor Michelle Hook. “We need to have science catch up and make sure that it is safe.”
The researchers also plan to test ketamine in combination with another existing drug, brimonidine, which is currently approved to treat glaucoma. Potter hopes that the drugs will produce additive effects for treating pain while cancelling out the negative side effects of each other. For example, brimonidine will lower pressure in the eye and brain while ketamine tends to raise pressure, so in theory, giving them together should keep pressure stable.
“We think that depression, pain, and tinnitus use multiple (but similar) neurological mechanisms,” Potter says, “so it makes sense that you would need to use multiple drugs that act at multiple sites in order to control these conditions.”
Source: Texas A&M University