Capsaicin is a topical analgesic that is FDA approved for the treatment of neuropathic pain associated with postherpetic neuralgia. Capsaicin is most often used as a topical analgesic and exists in many formulations of cream, liquid, and patch preparations of various strengths; however, it may also be found in some dietary supplements. Capsaicin is a naturally-occurring botanical irritant in chili peppers, synthetically derived for pharmaceutical formulations. Capsaicin is an agonist for the transient receptor potential vanilloid I receptor (TRPVI), which is an ion channel-receptor complex expressed on nociceptive nerve fibers in the skin. Common adverse reactions include erythema, rash, pruritus, nausea.

Naltrexone is marketed as its hydrochloride salt, naltrexone hydrochloride, under the trade names Revia and Depade. A once-monthly extended-release injectable formulation is marketed under the trade name Vivitrol. VIVITROL is indicated for the treatment of alcohol dependence in patients who are able to abstain from alcohol in an outpatient setting prior to initiation of treatment with VIVITROL. VIVITROL is indicated for the prevention of relapse to opioid dependence, following opioid detoxification. Naltrexone is a pure opiate antagonist and has little or no agonist activity. The mechanism of action of naltrexone in alcoholism is not understood; however, involvement of the endogenous opioid system is suggested by preclinical data. Naltrexone is thought to act as a competitive antagonist at mc, κ, and δ receptors in the CNS, with the highest affinity for the μ receptor. Naltrexone competitively binds to such receptors and may block the effects of endogenous opioids. This leads to the antagonization of most of the subjective and objective effects of opiates, including respiratory depression, miosis, euphoria, and drug craving. The major metabolite of naltrexone, 6-β-naltrexol, is also an opiate antagonist and may contribute to the antagonistic activity of the drug. Low dose naltrexone is an “off label” use of naltrexone. Normal naltrexone usage to break addictions is 50mg – 100mg. Usage of low dose naltrexone ranges in the area of 3 mg – 4.5 mg dosing and is prescribed in an oral pill form and is quite inexpensive. For people with multiple sclerosis, the dosage of LDN ranges from 1.5 to 4.5 ml per day.

Clonidine is a centrally acting α2 adrenergic agonist and imidazoline receptor agonist used to treat high blood pressure, attention deficit hyperactivity disorder, anxiety disorders, tic disorders, withdrawal (from either alcohol, opioids, or smoking), migraine, menopausal flushing, diarrhea, and certain pain conditions. Clonidine treats high blood pressure by stimulating α2 receptors in the brain, which decreases peripheral vascular resistance, lowering blood pressure. It has specificity towards the presynaptic α2 receptors in the vasomotor center in the brainstem. This binding decreases presynaptic calcium levels, thus inhibiting the release of norepinephrine (NE). It has also been proposed that the antihypertensive effect of clonidine is due to agonism on the I1 receptor (imidazoline receptor), which mediates the sympatho-inhibitory actions of imidazolines to lower blood pressure. Clonidines mechanism of action in the treatment of ADHD is to increase noradrenergic tone in the prefrontal cortex (PFC) directly by binding to postsynaptic α2A adrenergic receptors and indirectly by increasing norepinephrine input from the locus coeruleus. Clonidine indicated in the treatment of hypertension. Clonidine hydrochloride tablets may be employed alone or concomitantly with other antihypertensive agents. The US Food and Drug Administration (FDA) has approved clonidine for the treatment of attention deficit hyperactivity disorder (ADHD), under the trade name of Kapvay alone or with stimulants in 2010, for pediatric patients aged 6–17 years.

Ketamine (brand name Ketalar) is a cyclohexanone derivative used for induction of anesthesia. Ketalar is indicated as the sole anesthetic agent for diagnostic and surgical procedures that do not require skeletal muscle relaxation; also, it is indicated for the induction of anesthesia prior to the administration of other general anesthetic agents. Ketamine blocks NMDA receptors through an interaction with sites thought to be located within the ion channel pore region. However, the complete pharmacology of ketamine is more complex, and it is known to directly interact with a variety of other sites to varying degrees. Recently, it was shown that inclusion of the NR3B subunit does not alter the ketamine sensitivity of recombinant NR1/NR2 receptors expressed in oocytes. Likewise, 100 μM ketamine produced only weak inhibition of the glycine-induced current of NR1/NR3A/NR3B receptors. The side effects of ketamine noted in clinical studies include psychedelic symptoms (hallucinations, memory defects, panic attacks), nausea/vomiting, somnolence, cardiovascular stimulation and, in a minority of patients, hepatoxicity. The recreational use of ketamine is increasing and comes with a variety of additional risks ranging from bladder and renal complications to persistent psychotypical behaviour and memory defects. Ketamine was first synthesized in 1962 by Calvin Stevens at Parke-Davis Co (now Pfizer) as an alternative anesthetic to phencyclidine. It was first used in humans in 1965 by Corssen and Domino and was introduced into clinical practice by 1970.

Amitriptyline is a derivative of dibenzocycloheptadiene and a tricyclic antidepressant (TCA) and is mainly used to treat symptoms of depression. It works on the central nervous system (CNS) by inhibiting the membrane pump mechanism responsible for uptake of norepinephrine and serotonin in adrenergic and serotonergic neurons. Amitriptyline has been frequently used as an active comparator in clinical trials on newer antidepressants. It is rarely used as a first-line antidepressant nowadays due to its high degree of toxicity in overdose and generally poorer tolerability than the newer antidepressants.

Mepivicaine is a local anesthetic of the amide type. Mepivicaine as a reasonably rapid onset and medium duration and is known by the proprietary names as Carbocaine and Polocaine. Mepivicaine is used in local infiltration and regional anesthesia. Systemic absorption of local anesthetics produces effects on the cardiovascular and central nervous systems. At blood concentrations achieved with normal therapeutic doses, changes in cardiac conduction, excitability, refractoriness, contractility, and peripheral vascular resistance are minimal. Mepivicaine is used for production of local or regional analgesia and anesthesia by local infiltration, peripheral nerve block techniques, and central neural techniques including epidural and caudal blocks.

Capsaicin is a topical analgesic that is FDA approved for the treatment of neuropathic pain associated with postherpetic neuralgia. Capsaicin is most often used as a topical analgesic and exists in many formulations of cream, liquid, and patch preparations of various strengths; however, it may also be found in some dietary supplements. Capsaicin is a naturally-occurring botanical irritant in chili peppers, synthetically derived for pharmaceutical formulations. Capsaicin is an agonist for the transient receptor potential vanilloid I receptor (TRPVI), which is an ion channel-receptor complex expressed on nociceptive nerve fibers in the skin. Common adverse reactions include erythema, rash, pruritus, nausea.