Valproic acid (VPA; valproate; di-n-propylacetic acid, DPA; 2-propylpentanoic acid, or 2-propylvaleric acid) was first synthesized in 1882, by Burton. FDA approved valproic acid for the treatment of manic episodes associated with bipolar disorder, for the monotherapy and adjunctive therapy of complex partial seizures and simple and complex absence seizures and adjunctive therapy in patients with multiple seizure types that include absence seizures and for the prophylaxis of migraine headaches. The mechanisms of VPA which seem to be of clinical importance in the treatment of epilepsy include increased gamma-aminobutyric acid (GABA)-ergic activity, reduction in excitatory neurotransmission, and modification of monoamines. Recently, it was discovered that the VPA is a class I selective histone deacetylase inhibitor. This activity can be distinguished from its therapeutically exploited antiepileptic activity.

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.

Dexamethasone is an anti-inflammatory agent that is FDA approved for the treatment of many conditions, including rheumatic problems, a number of skin diseases, severe allergies, asthma, chronic obstructive lung disease, croup, brain swelling and others. Dexamethasone is a glucocorticoid agonist. Unbound dexamethasone crosses cell membranes and binds with high affinity to specific cytoplasmic glucocorticoid receptors. Adverse reactions are: Glaucoma with optic nerve damage, visual acuity and field defects; cataract formation; secondary ocular infection following suppression of host response; and perforation of the globe may occur; muscle weakness; osteoporosis and others. Aminoglutethimide may diminish adrenal suppression by corticosteroids. Macrolide antibiotics have been reported to cause a significant decrease in corticosteroid clearance.

Estradiol benzoate is the synthetic benzoate ester of estradiol, a steroid sex hormone vital to the maintenance of fertility and secondary sexual characteristics in females. As the primary, most potent estrogen hormone produced by the ovaries, estradiol binds to and activates specific nuclear receptors. This agent exhibits mild anabolic and metabolic properties, and increases blood coagulability. Although estradiol benzoate is not approved by the FDA for use in humans in the United States, it is approved for veterinary use as a subdermal implant both alone (CELERIN®) and in combination with the anabolic steroid trenbolone acetate (SYNOVEX® Plus).

Codeine is an opiate used to manage mild to moderate pain severe enough to require an opioid. Codeine is a selective agonist for the mu opioid receptor and has an affinity to delta and kappa-opioid receptors. In some countries, this drug is regulated under various narcotic control laws, because its chronic use can cause physical dependence. In others, it is available without a medical prescription in combination with paracetamol.

Morphine-6-glucuronide is a pharmacologically active metabolite of morphine that is being developed by CeNeS Pharmaceuticals as an alternative to morphine for the management of postoperative pain. Compared to morphine, Morphine-6-glucuronide has been reported to have6 and 86 times lower affinity for the human mu and kappa opioid receptors, respectively, and similar affinity for the delta opioid receptor. Morphine-6-glucuronide is was studied in phase III clinical trials for postoperative pain management. Unfortunately, Morphine-6-glucuronide failed to demonstrate superior safety compared to Morphine and further development was discontinued. Morphine-6-glucuronide accumulates after administration of morphine to patients with renal insufficiency, and analgesia can be obtained with lower doses of morphine compared to patients with normal renal function. More importantly, the dose should be reduced to avoid serious side-effects, although the simulations in this review did not account for side-effects.

Nebicapone (BIA 3-202) is a reversible, and tight-binding peripheral inhibitor of the enzyme catechol-O-methyltransferase (COMT) being developed for use as an adjunct to levodopa/dopa decarboxylase inhibitor in the treatment of PD. Nebicapone dose dependently and significantly decreased COMT activity. Nebicapone also increased systemic exposure to levodopa and improved motor response. The tight-binding nature of the inhibition produced by BIA 3-202 was evaluated by performing an Ackermann-Potter plot. The true K(i) for BIA 3-202, derived from the nonlinear regression analysis, was 0.19+/-0.02 nM. In substrate competition studies, an increase in the concentration of adrenaline resulted in a linear increase in IC(50) values for BIA 3-202.

Seliciclib (CYC202, R-roscovitine) is a second-generation orally available cyclin-dependent kinases (CDKs) inhibitor that competes for ATP binding sites on these kinases. It is a direct inhibitor of cyclin CDK2/E, CDK2/A and it has inhibitory effects on cyclin H/CDK7, CDK5, and CDK9. CDKs are enzymes that are central to the process of cell division and cell cycle control and play pivotal roles in cancer cell growth and DNA damage repair. Seliciclib exerts an anti-proliferative effect via several key mechanisms: selective downregulation of proliferative and survival proteins and upregulation of p53, leading to growth arrest or apoptosis. The second one is decreasing phosphorylation of Rb and modulating E2F transcriptional activity leading to growth arrest or apoptosis. Seliciclib is currently in phase II clinical trial as a drug candidate for the treatment of Cushing's disease and as a potential therapeutic agent for the treatment of cystic fibrosis (CF). In addition, it is in Phase II trials for non-small cell lung cancer and nasopharyngeal carcinoma.

Lersivirine (UK-453,061) is a novel second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI). It binds reverse transcriptase in a distinct way leading to a unique resistance profile. Lersivirine is a second-line NNRTI, which was investigated in a Phase IIb clinical trial. Lersivirine has shown encouraging virologic efficacy in a Phase IIa monotherapy study in NNRTI-naive patients. In a Phase IIb clinical trial in ART naive patients, clinical efficacy of lersivirine was compared with efavirenz, each administered together with tenofovir disoproxil fumarate/emtricitabine. After 48 weeks, lersivirine exhibited a slightly lower virologic response but similar immunologic efficacy. However, the trial was not powered for formal hypothesis testing of noninferiority of lersivirine. The development of lersivirine was recently stopped because the developing company determined that the compound would not provide an improvement over existing NNRTIs.