Esketamine is an S(+)-enantiomer of ketamine. It is a nonselective, noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptor. A nasal spray, containing esketamine, was approved in 2019 for the treatment of treatment-resistant depression in adults, in conjunction with an oral antidepressant, and is marketed under tradename SPARAVATO. Esketamine is a schedule III drug product in the USA.

Fentanyl is a potent agonist of mu opioid receptor. It is used to relieve severe pain, such as after surgery or during cancer treatment, and breakthrough pain (flare-ups of intense pain despite round-the-clock narcotic treatment). Fentanyl is an extremely powerful analgesic, 50–100-times more potent than morphine. Fentanyl harbors massive risk for addiction and abuse regardless of its prescription form. Fentanyl abuse is especially dangerous to those without a tolerance to opioids. The substance’s already elevated risk of overdose is multiplied when someone without a tolerance abuses it.

Haloperidol is a phenyl-piperidinyl-butyrophenone that is used primarily to treat schizophrenia and other psychoses. It is also used in schizoaffective disorder, delusional disorders, ballism, and Tourette syndrome (a drug of choice) and occasionally as adjunctive therapy in mental retardation and the chorea of Huntington disease. It is a potent antiemetic and is used in the treatment of intractable hiccups. Haloperidol also exerts sedative and antiemetic activity. Haloperidol principal pharmacological effects are similar to those of piperazine-derivative phenothiazines. The drug has action at all levels of the central nervous system-primarily at subcortical levels-as well as on multiple organ systems. Haloperidol has strong antiadrenergic and weaker peripheral anticholinergic activity; ganglionic blocking action is relatively slight. It also possesses slight antihistaminic and antiserotonin activity. The precise mechanism whereby the therapeutic effects of haloperidol are produced is not known, but the drug appears to depress the CNS at the subcortical level of the brain, midbrain, and brain stem reticular formation. Haloperidol seems to inhibit the ascending reticular activating system of the brain stem (possibly through the caudate nucleus), thereby interrupting the impulse between the diencephalon and the cortex. The drug may antagonize the actions of glutamic acid within the extrapyramidal system, and inhibitions of catecholamine receptors may also contribute to haloperidol's mechanism of action. Haloperidol may also inhibit the reuptake of various neurotransmitters in the midbrain, and appears to have a strong central antidopaminergic and weak central anticholinergic activity. The drug produces catalepsy and inhibits spontaneous motor activity and conditioned avoidance behaviours in animals. The exact mechanism of antiemetic action of haloperidol has also not been fully determined, but the drug has been shown to directly affect the chemoreceptor trigger zone (CTZ) through the blocking of dopamine receptors in the CTZ. Haloperidol is marketed under the trade name Haldol among others.

Protriptyline (trade name Vivactil) is a tricyclic antidepressant, indicated for the treatment of depression. Protriptyline acts by decreasing the reuptake of norepinephrine and to a lesser extent serotonin (5-HT) in the brain. Tricyclic antidepressants act to change the balance of naturally occurring chemicals in the brain that regulate the transmission of nerve impulses between cells. Protriptyline increases the concentration of norepinephrine and serotonin (both chemicals that stimulate nerve cells) and, to a lesser extent, blocks the action of another brain chemical, acetylcholine. The therapeutic effects of protriptyline, like other antidepressants, appear slowly. Maximum benefit is often not evident for at least two weeks after starting the drug. Protriptyline is used primarily to treat depression and to treat the combination of symptoms of anxiety and depression. Like most antidepressants of this chemical and pharmacological class, protriptyline has also been used in limited numbers of patients to treat panic disorder, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, enuresis, eating disorders such as bulimia nervosa, cocaine dependency, and the depressive phase of bipolar disorder (manic-depressive) disorder. It has also been used to support smoking cessation programs. Like all tricyclic antidepressants, protriptyline should be used cautiously and with close physician supervision. This is especially so in the elderly, or people who have benign prostatic hypertrophy (enlarged prostate gland), or urinary retention, or glaucoma, especially angle-closure glaucoma (the most severe form). Before starting treatment, people should discuss the relative risks and benefits of treatment with their doctors to help determine if protriptyline is the right antidepressant for them. A common problem with tricyclic antidepressants is sedation (drowsiness, lack of physical and mental alertness), but protriptyline is considered the least sedating agent among this class of agents. Its side effects are especially noticeable early in therapy. In most people, early tricyclic side-effects decrease or disappear entirely with time, but, until then, patients taking protriptyline should take care to assess which side-effects occur in them and should not perform hazardous activities requiring mental acuity or coordination. The side-effects are increased when protriptyline is taken with central nervous system depressants, such as alcoholic beverages, sleeping medications, other sedatives, or antihistamines, as well as with other antidepressants including SSRIs, SNRIs or monoamine oxidase Inhibitors.

Pentazocine is a synthetically prepared prototypical mixed agonist-antagonist narcotic (opioid analgesic) drug of the benzomorphan class of opioids used to treat moderate to moderately severe pain. Pentazocine is sold under several brand names, such as Fortral, Sosegon, Talwin NX. Pentazocine acts as an agonist of κ-opioid receptors and as an antagonist of μ-opioid receptors. This compound may exist as one of two enantiomers, named (+)-pentazocine and (−)-pentazocine. Side effects are similar to those of morphine, but pentazocine, due to its action at the kappa opioid receptor is more likely to invoke psychotomimetic effects. High dose may cause high blood pressure or high heart rate.

Thiothixene (trade mark Navane) belongs to a class of antipsychotics known as the first-generation antipsychotics, sometimes referred to as conventional or typical antipsychotics. Thiothixene is a thioxanthene antipsychotic which elicits antipsychotic activity by postsynaptic blockade of CNS dopamine receptors resulting in inhibition of dopamine-mediated effects; also has alpha-adrenergic blocking activity. Thiothixene is effective in the management of schizophrenia. Only cis isomer of thiothixene exerts clinical effectivity.

Amantadine hydrochloride has pharmacological actions as both an anti-Parkinson and an antiviral drug. The mechanism by which amantadine exerts its antiviral activity is not clearly understood. It appears to mainly prevent the release of infectious viral nucleic acid into the host cell by interfering with the function of the transmembrane domain of the viral M2 protein. In certain cases, amantadine is also known to prevent virus assembly during virus replication. It does not appear to interfere with the immunogenicity of inactivated influenza A virus vaccine. The mechanism of action of amantadine in the treatment of Parkinson's disease and drug-induced extrapyramidal reactions is not known. Data from earlier animal studies suggest that amantadine hydrochloride may have direct and indirect effects on dopamine neurons. More recent studies have demonstrated that amantadine is a weak, non-competitive NMDA receptor antagonist (K1 = 10µM). Although amantadine has not been shown to possess direct anticholinergic activity in animal studies, clinically, it exhibits anticholinergic-like side effects such as dry mouth, urinary retention, and constipation. Amantadine was approved by the FDA in 1966 as a prophylactic agent against Asian influenza, and eventually received approval for the treatment of influenza virus A in adults. In 1969, it was also discovered by accident to help reduce symptoms of Parkinson's disease, drug-induced extrapyramidal syndromes, and akathisia.

Oxazepam is the first of a chemical series of compounds, the 3-hydroxybenzodiazepinones. A therapeutic agent providing versatility and flexibility in control of common emotional disturbances, this product exerts prompt action in a wide variety of disorders associated with anxiety, tension, agitation and irritability, and anxiety associated with depression. Oxazepam has distinguished itself clinically from other benzodiazepines by virtue of its excellent tolerance. Because of its excellent tolerance, dosage is very flexible, and it is, therefore, possible to utilize oxazepam in a wide spectrum of anxiety-related disorders including the psychoses. Oxazepam has been administered to humans by the oral route only. Usual ranges for kinetic parameters are: elimination half-life, 5 to 15 hours; volume of distribution, 0.6 to 2.0 L/kg; clearance, 0.9 to 2.0 ml/min/kg. Age and liver disease have a minimal influence on oxazepam kinetics, but renal disease is associated with a prolonged half-life and increased volume of distribution.

Prilocaine is a local anesthetic that is similar pharmacologically to lidocaine. Prilocaine binds to the intracellular surface of sodium channels which blocks the subsequent influx of sodium into the cell. Action potential propagation and never function is, therefore, prevented. This block is reversible and when the drug diffuses away from the cell, sodium channel function is restored and nerve propagation returns. Prilocaine acts on sodium channels on the neuronal cell membrane, limiting the spread of seizure activity and reducing seizure propagation. The antiarrhythmic actions are mediated through effects on sodium channels in Purkinje fibers. Currently, Prilocaine is used most often for infiltration anesthesia in dentistry.

Nortriptyline is a second-generation tricyclic antidepressant (TCA) marketed as the hydrochloride salt under the trade names Sensoval, Aventyl, Pamelor, Norpress, Allegron, Noritren and Nortrilen. Nortriptyline is used in the treatment of depression and childhood nocturnal enuresis. Its off-label uses include treatment of postherpetic neuralgia, angioedema and smoking Cessation, and attention deficit hyperactivity disorder in some neurological disorders. It is believed that nortriptyline either inhibits the reuptake of the neurotransmitter serotonin at the neuronal membrane or acts at beta-adrenergic receptors. Nortriptyline is US FDA-approved for the treatment of major depression. In the United Kingdom, it may also be used for treating nocturnal enuresis, with courses of treatment lasting no more than three months. The most common side effects include dry mouth, sedation, constipation, and increased appetite, mild blurred vision, tinnitus, occasionally hypomania or mania. An occasional side effect is a rapid or irregular heartbeat. Alcohol may exacerbate some of its side effects. However, fewer and milder side effects occur with nortriptyline than tertiary tricyclic antidepressants such as imipramine and amitriptyline. For this reason, nortriptyline is preferred to other tricyclic antidepressants, particularly with older adults, which also improves compliance.