Sedative medications are neurological depressants. As depressants of the neurological system have anxiolytic, or anti-anxiety, effects, many sedatives are used successfully as anti-anxiety drugs. Sedatives also have analgesic, or pain-relieving, effect either independently or by virtue of calming down the neurological system. There are many sedatives prescribed for pain and anxiety relief.
Barbiturates
Barbiturates belong to an older class of sedatives still used in euthanasia, as pain relievers and to induce anesthesia. Barbiturates bind to the brain's GABA receptor. GABA is a neurological inhibitor that slows down the neurological system. Barbiturates enhance this effect by causing the receptor's chloride ion channel to stay open for a longer time. Chloride ions traveling through the channel into neurons block the release of other neurotransmitters, reports a study published in the October 2002 issue of "Journal of Clinical Investigation."
Many effective migraine medications contain a barbiturate, such as butalbital, in addition to an over-the-counter analgesic. The barbiturate enhances the effect of the analgesic drug and provides a calming effect on the neurological system.
Benzodiazepines
Benzodiazepines replaced barbiturates as anti-anxiety drugs when they entered the popular market in the 1960s. They are now the main anti-anxiety drugs prescribed for immediate relief of anxiety. Though they are chemically unlike barbiturates, their mechanism of action is quite similar. Like barbiturates, they also bind to the GABA receptor, albeit at a different site, which causes the receptor to open more frequently.
Benzodiazepines can provide relief of chronic pain when injected directly into the spine, according to a study published in the January 2008 issue of "Nature." Taken orally, benzodiazepines do not have independent analgesic properties but the neuron retardation they give rise to can alleviate pain symptoms to some extent.
Imidazopyridines
The newest class of GABA agonists prescribed as sedatives are the imidazopyridines. They include the widely discussed sleeping pill zolpidem, or Ambien, which causes sleep-driving and sleep-eating in some patients, according to a report published in the October 2009 issue of "Journal of Clinical Sleep Medicine."
Imidazopyrines exert their sedative effect by binding to the GABA receptor at a different site than barbiturates and benzodiazepines, thereby causing neuron activity to slow down. Like barbiturates and benzodiazepines, they can alleviate symptoms of anxiety and pain.
Opioids
The most commonly prescribed opioids are methadone, morphine and codeine. Methadone is mainly used to treat heroin addiction but it is also an effective pain reliever. Like the body's own endorphins, opioid drugs relieve pain by binding to the mu-opioid receptor, according to a study published in the June 2004 issue of "Science."
Opioids also block the NMDA glutamate receptor. Glutamate is the brain's main excitatory neurotransmitter. Blocking the NMDA glutamate receptor is what accounts for the sedative effects of opioid drugs.
Methadone also acts as a serotonin reuptake inhibitor, according to a report published in the September 2003 issue of "Journal of Supportive Oncology." This prevents serotonin from being transported back into the brain's neurons. Serotonin in higher concentrations can down-regulate fear processing in the brain's limbic fear center. This, in addition to the down-regulation of glutamate, may explain some of the drug's anxiolytic properties.
References
- "Journal of Clinical Investigation"; Decreased Anxiety-Like Behavior, Reduced Stress Hormones, and Neurosteroid Supersensitivity in Mice Lacking Protein Kinase Cε; Clyde W. Hodge, et al.; October 2002
- "Nature"; Reversal of Pathological Pain Through Specific Spinal GABAA Receptor Subtypes; Julia Knabl, et al.; January 2008
- "Journal of Clinical Sleep Medicine"; Zolpidem-Induced Sleepwalking, Sleep Related Eating Disorder, and Sleep-Driving; R. Hoque and A. L. Chesson Jr.; October 2009
- "Science"; Deficit in Attachment Behavior in Mice Lacking the Mu-Opioid Receptor Gene; A. Moles, et al.; June 2004
- "The Journal of Supportive Oncology"; Prescribing Methadone, A Unique Analgesic; Paolo L. Manfredi and Raymond W. Houde; September 2003
