Oxygen is a chemical element with atomic number 8. Diatomic oxygen constitutes 20.8% of the Earth's atmosphere. Diatomic oxygen is used by complex life forms such as animals, in cellular respiration. Medical oxygen is widely used in clinical practice to provide a basis for most modern anaesthetic techniques; to restore the tissue oxygen tension towards normal by improving oxygen availability in a wide range of conditions such as shock, severe haemorrhage, coronary occlusion, carbon monoxide poisoning, major trauma; to aid the resuscitation of the critically ill, when the circulation is impaired; to aid in neonatal resuscitation; to treat acute severe headache in adults diagnosed with cluster headache.

Cocaine is an alkaloid ester extracted from the leaves of plants including coca. Cocaine is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake. Cocaine is addictive due to its effect on the reward pathway in the brain. After a short period of use, there is a high risk that dependence will occur. Its use also increases the risk of stroke, myocardial infarction, lung problems in those who smoke it, blood infections, and sudden cardiac death. Cocaine sold on the street is commonly mixed with local anesthetics, cornstarch, quinine, or sugar which can result in additional toxicity. Following repeated doses, a person may have decreased the ability to feel pleasure and be very physically tired. Cocaine acts by inhibiting the reuptake of serotonin, norepinephrine, and dopamine. This results in greater concentrations of these three neurotransmitters in the brain. It can easily cross the blood-brain barrier and may lead to the breakdown of the barrier.

Nitrous oxide (N2O, laughing gas) was first discovered by the English scientist Joseph Priestly and has been used for more than 150 years. It has remained one of the most widely used anesthetics in both dental and medical applications. This small and simple inorganic chemical molecule has indisputable effects of analgesia, anxiolysis, and anesthesia that are of great clinical interest. As a general anesthetic, it is very weak and is generally not used as a single agent. It may be used as a carrier gas with oxygen in combination with more potent general inhalational gases for surgical anesthesia. In dentistry, it is commonly used as a single agent (with oxygen) for partial sedation, most commonly in pediatric dental populations. Findings to date indicate that the analgesic effect of N2O is opioid in nature, and, like morphine, may involve a myriad of neuromodulators in the spinal cord. The anxiolytic effect of N2O, on the other hand, resembles that of benzodiazepines and may be initiated at selected subunits of the gamma-aminobutyric acid type A (GABA(A)) receptor. Similarly, the anesthetic effect of N2O may involve actions at GABA(A) receptors and possibly at N-methyl-D-aspartate receptors as well.

Morphine is one of the most important and widely used opioid for the treatment of chronic and acute pain: the very wide interindividual variability in the patients’ response to the drug may have genetic derivations. Sulphate salt of morphine sold under the many brand names, one of them, DURAMORPH, which is indicated for the management of pain severe enough to require use of an opioid analgesic by intravenous administration, and for which alternative treatments are not expected to be adequate. In addition for the epidural or intrathecal management of pain without attendant loss of motor, sensory, or sympathetic function. Morphine is a full opioid agonist and is relatively selective for the mu-opioid receptor, although it can bind to other opioid receptors at higher doses. The principal therapeutic action of morphine is analgesia. Like all full opioid agonists, there is no ceiling effect for analgesia with morphine. The precise mechanism of the analgesic action is unknown. However, specific CNS opioid receptors for endogenous compounds with opioid-like activity have been identified throughout the brain and spinal cord and are thought to play a role in the analgesic effects of this drug. Morphine has a high potential for addiction and abuse. Common side effects include drowsiness, vomiting, and constipation. Caution is advised when used during pregnancy or breast-feeding, as morphine will affect the baby.

Alcohols exhibit rapid broad-spectrum antimicrobial activity against vegetative bacteria (including mycobacteria), viruses, and fungi but are not sporicidal. They are, however, known to inhibit sporulation and spore germination, but this effect is reversible. Because of the lack of sporicidal activity, alcohols are not recommended for sterilization but are widely used for both hard-surface disinfection and skin antisepsis. Lower concentrations may also be used as preservatives and to potentiate the activity of other biocides. Many alcohol products include low levels of other biocides (in particular chlorhexidine), which remain on the skin following evaporation of the alcohol, or excipients (including emollients), which decrease the evaporation time of the alcohol and can significantly increase product efficacy. Ethanol in combination with: chlorhexidine gluconate 1% was approved to use in surgical hand antiseptic. It significantly reduces the number of microorganisms on the hands and forearms prior to surgery or patient care. Ethanol is also used as a co-solvent to dissolve many insoluble drugs and to serve as a mild sedative in some medicinal formulations. Ethanol is metabolized by the hepatic enzyme alcohol dehydrogenase. Ethanol affects the brain’s neurons in several ways. It alters their membranes as well as their ion channels, enzymes, and receptors. Alcohol also binds directly to the receptors for acetylcholine, serotonin, GABA, and the NMDA receptors for glutamate. The sedative effects of ethanol are mediated through binding to GABA receptors and glycine receptors (alpha 1 and alpha 2 subunits). It also inhibits NMDA receptor functioning. In its role as an anti-infective, ethanol acts as an osmolyte or dehydrating agent that disrupts the osmotic balance across cell membranes.

Levomethamphetamine is the levorotary (L-enantiomer) form of methamphetamine. Levomethamphetamine is a sympathomimetic vasoconstrictor which is the active ingredient in some over-the-counter (OTC) nasal decongestant inhalers in the United States. Levomethamphetamine crosses the blood-brain-barrier and acts as a TAAR1 agonist, functioning as a selective norepinephrine releasing agent (with few or no effects on the release of dopamine), so it affects the central nervous system, although its effects are qualitatively distinct relative to those of dextromethamphetamine. Levomethamphetamine does not possess the potential for euphoria or addiction that dextromethamphetamine possesses. Among its physiological effects are the vasoconstriction that makes it useful for nasal decongestion. The elimination half-life of levomethamphetamine is between 13.3 and 15 hours, whereas dextromethamphetamine has a half-life of about 10.5 hours. When the nasal decongestant is taken in excess, levomethamphetamine has potential side effects resembling those of other sympathomimetic drugs; these effects include hypertension (elevated blood pressure), tachycardia (rapid heart rate), nausea, stomach cramps, dizziness, headache, sweating, muscle tension, and tremors. Central side effects may include anxiety, insomnia, and anorexia

A sulfide ion is composed of a lone sulfur atom. Its charge is negative two, giving sulfides this formula: S^2-. Sulfide is a strong base, so solutions of sulfide in water are basic, due to hydrolysis. One well-known ionic compound with a sulfide ion is H_2S. The infamous rotten-egg smell often associated with sulfur originates from this compound. Sodium sulfide nonahydrate is used in the formation of surface functionalized cadmium sulfide quantum dots.