Roadblocks to Opiate Abuse
Roadblocks to Opiate Abuse
Many individuals live with pain, either chronic or acute. An estimated 100 million Americans suffer from chronic pain.1 Pain causes stress and suppresses immune responses, which make medical problems worse. The use of opiates to manage pain has increased. Unfortunately, along with the rise in opiate prescriptions is the increase in abuse. By 2012, 2.1 million Americans were addicted to prescription opiates.2 Opiates for pain relief were involved in 14,800 drug overdose deaths in 2008 versus 11,500 in 2007.3
To combat opiate abuse and its dire consequences, drug makers developed many strategies. Some formulations allow active medicine for pain relief while blocking excessive blood levels at receptors. Other strategies alter opiate availability in a physical manner, so that drugs can no longer be snorted, injected, or dissolved.4
Opiates act on specific receptors that evolved to respond to endogenous opiates such as dynorphin and enkephalin. Receptors include μ, δ, and Κ, distributed at γ-aminobutyric acid (GABA)-releasing axons. They can inhibit GABA release onto dopamine-producing neurons in the nucleus accumbens, increasing dopamine-induced pain relief. Unfortunately, in addition to relieving pain, dopamine is also heavily implicated in addiction. Many newer opiate formulations are designed to achieve a balance at receptors, relieving pain but blocking excessive levels associated with abuse and addiction.
Partial blocking with naloxone
Approved in 2002 for opiate dependence, Suboxone is a combination of buprenorphine and naloxone in a 4:1 ratio. In addition to treating abuse, it is used as therapy for chronic pain. Buprenorphine is a partial opioid agonist at μ-opioid receptors and an antagonist at κ-opioid receptors. By itself, buprenorphine relieves pain, but because it is an antagonist at higher doses, it can prevent abuse. The addition of naloxone adds further abuse prevention, as an opioid antagonist with no agonist activity.
Embeda, a morphine/naltrexone analgesic, is a gelatin capsule of the μ-opioid antagonist naltrexone within a morphine-containing pill. The naltrexone is released if the tablet is crushed, blocking the opiate effects of morphine. If the pill is taken as intended, naltrexone has a minimal effect.
Another medication, under development with Elite Pharmaceuticals, is ELI-216, which is a combination of oxycodone and naltrexone. ELI-216 is similar to Embeda in that naltrexone is only released when the medication is crushed, dissolved, or otherwise extracted. Naltrexone in this case is sequestered within small beads placed inside the gel capsule.
Drug manufacturers have developed several different technologies that allow for pain management but deter abuse on the basis of their physical properties alone. For example, Opana ER, marketed by Endo Pharmaceuticals, is a controlled-release oxymorphone in a drug matrix called INTAC Technology, created by the company Grünenthal. INTAC makes a drug resistant to crushing, dissolving, cutting, and chewing. Even when the medication has been tampered with, release properties stay the same. According to an informational brochure released by Grünenthal, this is based on “polyethylenoxide (PEO) of high molecular weight and a proprietary hot-melt extrusion process that combines the two factors of heat and pressure.”
With similar intentions to prevent pill manipulation, Acura Pharmaceuticals has developed Aversion technology. Three different strategies prevent abuse, although all are not incorporated into one medication. For example, if the medication is crushed, it turns into nasal cavity irritating chunks. When mixed with liquid, it becomes a difficult-to-inject gel. The third strategy is the addition of niacin to an opiate, which causes itching, headache, and chills when too much is ingested. Symptoms go away after about 90 minutes.