Levodopa (L-DOPA) was first isolated from seedlings of Vicia faba by Marcus Guggenheim in 1913. Levodopa, a dopamine precursor, is an effective and well-tolerated dopamine replacement agent used to treat Parkinson's disease. Oral levodopa has been widely used for over 40 years, often in combination with a dopa-decarboxylase inhibitor carbidopa, which reduces many treatment complications, extending its half-life and increasing levodopa availability to the brain. Entacapone, a catechol-O-methyltransferase inhibitor, can also be used to improve the bioavailability of levodopa, especially when used in conjunction with a carbidopa.

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.

Clindamycin hydrochloride is the hydrated hydrochloride salt of clindamycin. Clindamycin is a semisynthetic antibiotic produced by a 7(S)-chloro-substitution of the 7(R)-hydroxyl group of the parent compound lincomycin. Clindamycin inhibits bacterial protein synthesis by binding to the 50S subunit of the ribosome. It has activity against Gram-positive aerobes and anaerobes as well as some Gram-negative anaerobes.

Flurazepam (known under the brand names Dalmane and Dalmadorm) is a drug which is a benzodiazepine derivative. It is a hypnotic agent which does not appear to decrease dream time as measured by rapid eye movements (REM). Furthermore, it decreases sleep latency and number of awakenings for a consequent increase in total sleep time. Flurazepam binds to an allosteric site on GABA-A receptors. Binding potentiates the action of GABA on GABA-A receptors by opening the chloride channel within the receptor, causing chloride influx and hyperpolarization. Flurazepam is useful for the treatment of insomnia characterized by difficulty in falling asleep, frequent nocturnal awakenings, and/or early morning awakening. Flurazepam can be used effectively in patients with recurring insomnia or poor sleeping habits, and in acute or chronic medical situations requiring restful sleep.

Floxuridine is a pyrimidine analog that acts as an inhibitor of the S-phase of cell division. This selectively kills rapidly dividing cells. Floxuridine is an anti-metabolite. Anti-metabolites masquerade as pyramidine-like molecules which prevents normal pyrimidines from being incorporated into DNA during the S phase of the cell cycle. Flurouracil (the end-product of catabolism of floxuridine) blocks an enzyme which converts cytosine nucleosides into the deoxy derivative. In addition, DNA synthesis is further inhibited because fluoruracil blocks the incorporation of the thymdine nucleotide into the DNA strand. Floxuridine is used for palliative management of gastrointestinal adenocarcinoma metastatic to the liver, when given by continuous regional intra-arterial infusion in carefully selected patients who are considered incurable by surgery or other means. Also for the palliative management of liver cancer (usually administered by hepatic intra-arterial infusion).Floxuridine first gained FDA approval in December 1970 under the brand name FUDR. The drug was initially marketed by Roche, which also did a lot of the initial work on 5-fluorouracil. The National Cancer Institute was an early developer of the drug. Roche sold its FUDR product line in 2001 to F H Faulding, which became Mayne Pharma.

Penicillamine, sold under the trade names of Cuprimine among others, is a medication primarily used for treatment of Wilson's disease, cystinuria and active rheumatoid arthritis. Penicillamine is a chelating agent recommended for the removal of excess copper in patients with Wilson's disease. From in vitro studies which indicate that one atom of copper combines with two molecules of penicillamine. Penicillamine also reduces excess cystine excretion in cystinuria. This is done, at least in part, by disulfide interchange between penicillamine and cystine, resulting in formation of penicillamine-cysteine disulfide, a substance that is much more soluble than cystine and is excreted readily. Penicillamine interferes with the formation of cross-links between tropocollagen molecules and cleaves them when newly formed. The mechanism of action of penicillamine in rheumatoid arthritis is unknown although it appears to suppress disease activity. Unlike cytotoxic immunosuppressants, penicillamine markedly lowers IgM rheumatoid factor but produces no significant depression in absolute levels of serum immunoglobulins. Also unlike cytotoxic immunosuppressants which act on both, penicillamine in vitro depresses T-cell activity but not B-cell activity.

Procarbazine is a chemotherapy medication used for the treatment of Hodgkin's lymphoma and brain cancers. For Hodgkin's it is often used together with mechlorethamine, vincristine, and prednisone while for brain cancers such as glioblastoma multiforme it is used with lomustine and vincristine. Procarbazine inhibits DNA, RNA, and protein synthesis by inhibiting transmethylation of methionine into transfer RNA; may also damage DNA directly through alkylation. Common side effect include low blood cell counts and vomiting. Other side effects include tiredness and depression.

Cytarabine is a pyrimidine nucleoside analog. Cytarabine or cytosine arabinoside (Cytosar-U or Depocyt) is a chemotherapy agent used mainly in the treatment of cancers of white blood cells such as acute myeloid leukemia (AML) and non-Hodgkin lymphoma. It also has antiviral and immunosuppressant properties. Cytarabine is an antimetabolite antineoplastic agent that inhibits the synthesis of DNA. It is a cell cycle phase-specific, affecting cells only during the S phase of cell division. Intracellularly, cytarabine is converted into cytarabine-5-triphosphate (ara-CTP), which is the active metabolite. The mechanism of action is not completely understood, but it appears that ara-CTP acts primarily through inhibition of DNA polymerase. Incorporation into DNA and RNA may also contribute to cytarabine cytotoxicity. Cytarabine is cytotoxic to a wide variety of proliferating mammalian cells in culture.The drug has a short plasma half-life, low stability and limited bioavailability. Overdosing of patients with continuous infusions may lead to side effects. Thus, various prodrug strategies and delivery systems have been explored extensively to enhance the half-life, stability and delivery of cytarabine. Alternative, delivery systems of cytarabine have emerged for the treatment of different cancers. The liposomal-cytarabine formulation has been approved for the treatment of lymphomatous meningitis.

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.

Azathioprine remains one of the most important and widely prescribed drugs for immunosuppression/immunomodulation in autoimmune disease over 30 years after its introduction. Azathioprine is licensed for the treatment of only a limited range of autoimmune disorders, which is probably a reflection on the age of the drug. Widening the license for a drug is both costly and time consuming, and it would make no commercial sense for manufacturers to do so, at this late stage of life, for azathioprine. However, azathioprine is now so well established as an immunomodulating drug in autoimmune disorders that it represents the gold standard by which other drugs are compared. Azathioprine is indicated as an adjunct for the prevention of rejection in renal homotransplantation. It is also indicated for the management of active rheumatoid arthritis to reduce signs and symptoms. The combined use of azathioprine tablets with disease modifying anti-rheumatic drugs (DMARDs) has not been studied for either added benefit or unexpected adverse effects. The use of azathioprine tablets with these agents cannot be recommended. Azathioprine is a pro-drug, converted in the body to the active metabolite 6-mercaptopurine. Azathioprine acts to inhibit purine synthesis necessary for the proliferation of cells, especially leukocytes and lymphocytes. It is a safe and effective drug used alone in certain autoimmune diseases, or in combination with other immunosuppressants in organ transplantation. Its most severe side effect is bone marrow suppression, and it should not be given in conjunction with purine analogues such as allopurinol. The enzyme thiopurine S-methyltransferase (TPMT) deactivates 6-mercaptopurine. Genetic polymorphisms of TPMT can lead to excessive drug toxicity, thus assay of serum TPMT may be useful to prevent this complication. Azathioprine is metabolized to 6-mercaptopurine (6-MP). Both compounds are rapidly eliminated from blood and are oxidized or methylated in erythrocytes and liver; no azathioprine or mercaptopurine is detectable in urine after 8 hours. Activation of 6-mercaptopurine occurs via hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and a series of multi-enzymatic processes involving kinases to form 6-thioguanine nucleotides (6-TGNs) as major metabolites.