Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere. Nitrogen occurs in all living organisms. It is a constituent element of amino acids and therefore of proteins and nucleic acids (DNA and RNA). Nitrogen is found in the chemical structure of almost all neurotransmitters and is a key component of alkaloids. Specific bacteria (e. g. Rhizobium trifolium) possess nitrogenase enzymes which can fix atmospheric nitrogen into a form (ammonium ion) which is chemically useful to higher organisms. Animals use nitrogen-containing amino acids from plant sources, as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of proteins and nucleic acids. Animal metabolism of NO (nitric oxide) results in production of nitrite. Animal metabolism of nitrogen in proteins generally results in excretion of urea, while animal metabolism of nucleic acids results in excretion of urea and uric acid. The characteristic odor of animal flesh decay is caused by nitrogen-containing long-chain amines, such as putrescine and cadaverine. Decay of organisms and their waste products may produce small amounts of nitrate, but most decay eventually returns nitrogen content to the atmosphere, as molecular nitrogen. The circulation of nitrogen from the atmosphere through organics and then back to the atmosphere is commonly referred to as the nitrogen cycle. Nitrogen can be measured in urine with the Kjeldahl method or by spectrophotometric methods (enzymic tests). Total urinary nitrogen is calculated based on urea urinary nitrogen quantified with these methods. Liquid nitrogen (E941) is widely used in food industry as a freezing agent and as a protection against the impact of microorganisms. Nitrogen (E941) extends the period of validity of food and maintains its nutrients and is also used for packing products. In other fields of industry, nitrogen (E941) is useful in suppressing the combustion processes and in creating protective environment in order to avoid oxidation. Medical nitrogen has various medical uses, especially in liquid form when it provides temperatures as low as -196° C. Applications of medical nitrogen in the healthcare environment may include the following: * In cryopreservation for the long-term preservation of blood, blood components, other cells, body fluids or tissue samples. * In cryosurgery for minor surgical procedures in dermatology. * As a component in many gas mixtures. * As a displacement medium for sterile equipment, a non-oxidising displacement medium in pharmaceutical vials and as a propellant in pressurised aerosol dispensers. * As a source of pneumatic pressure to power gas-operated medical devices. * As a coolant for carbon dioxide surgical lasers.

Methenamine is an antibacterial agent for preventing recurrent urinary tract infection. It can be used as methenamine hippurate or methenamine mandelate preparations and is United States Food and Drug Administration-approved. Methenamine exerts its activity because it is hydrolyzed to formaldehyde in acid urine.

Apomorphine (brand names: Apokyn, Ixense, Spontane, Uprima) is indicated for the acute, intermittent treatment of hypomobility, “off” episodes (“end-of-dose wearing off” and unpredictable “on/off” episodes) in patients with advanced Parkinson’s disease. Apomorphine has been studied as an adjunct to other medications. It is a non-ergoline dopamine agonist with high in vitro binding affinity for the dopamine D4 receptor, and moderate affinity for the dopamine D2, D3, and D5, and adrenergic α1D, α2B, α2C receptors. The precise mechanism of action as a treatment for Parkinson’s disease is unknown, although it is believed to be due to stimulation of post-synaptic dopamine D2-type receptors within the caudate-putamen in the brain.

Betaine is a methyl derivative of glycine first isolated from the juice of sugar beets. Betaine is found in many common foods, but concentrated significantly in beets, spinach, wheat foods, and shellfish. In addition, betaine can be synthesized within the human body. Betaine participates in the methionine cycle, which produces vital biomolecules including proteins, hormones, phospholipids, polyamines, and nutrients. Betaine is used as a dietary supplement and has a beneficial effect on the human health. In the USA, FDA approved a betaine-containing drug Cystadane for the treatment of homocystinuria. The drug acts as a methyl group donor in the remethylation of homocysteine to methionine.

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.