Zileuton is an asthma drug that differs chemically and pharmacologically from other antiasthmatic agents. It blocks leukotriene synthesis by inhibiting 5-lipoxygenase, an enzyme of the eicosanoid synthesis pathway. Current data indicates that asthma is a chronic inflammatory disorder of the airways involving the production and activity of several endogenous inflammatory mediators, including leukotrienes. Sulfido-peptide leukotrienes (LTC4, LTD4, LTE4, also known as the slow-releasing substances of anaphylaxis) and LTB4, a chemoattractant for neutrophils and eosinophils, are derived from the initial unstable product of arachidonic acid metabolism, leukotriene A4 (LTA4), and can be measured in a number of biological fluids including bronchoalveolar lavage fluid (BALF) from asthmatic patients. In humans, pretreatment with zileuton attenuated bronchoconstriction caused by cold air challenge in patients with asthma. Zileuton is a specific inhibitor of 5-lipoxygenase and thus inhibits leukotriene (LTB4, LTC4, LTD4, and LTE4) formation. Both the R(+) and S(-) enantiomers are pharmacologically active as 5-lipoxygenase inhibitors in in vitro systems. Leukotrienes are substances that induce numerous biological effects including augmentation of neutrophil and eosinophil migration, neutrophil and monocyte aggregation, leukocyte adhesion, increased capillary permeability, and smooth muscle contraction. These effects contribute to inflammation, edema, mucus secretion, and bronchoconstriction in the airways of asthmatic patients. Zileuton is marketed under the trade name ZYFLO.

Olanzapine is a novel antipsychotic agent marketed by Lilly & Co. It has a pleotrophic pharmacology and affects dopaminergic, serotonergic, muscarinic and adrenergic activities. Olanzapine is used to treat the symptoms of psychotic conditions such as schizophrenia and bipolar disorder (manic depression) in adults and children who are at least 13 years old. Olanzapine is sometimes used together with other antipsychotic medications or antidepressants. The mechanism of action of olanzapine, as with other drugs having efficacy in schizophrenia, is unknown. However, it has been proposed that this drug’s efficacy in schizophrenia is mediated through a combination of dopamine and serotonin type 2 (5HT2) antagonism. The mechanism of action of olanzapine in the treatment of acute manic or mixed episodes associated with bipolar I disorder is unknown. Olanzapine treatment led to rapid phosphorylation of kinases from all three pathways in PC12 cells. Phosphorylation of Akt was blocked with selective inhibitors (wortmannin and LY294002), which implicates phosphoinositide 3-kinase (PI3K) in the signaling cascade. Short-term mitogenic effects of olanzapine were abolished with a selective inhibitor of Akt, but not by inhibition of the ERK pathway. Olanzapine is metabolized by the cytochrome P450 system; principally by isozyme 1A2 and to a lesser extent by 2D6. By these mechanisms more than 40% of the oral dose, on average, is removed by the hepatic first-pass effect. Drugs or agents that increase the activity of CYP1A2, notably tobacco smoke, may significantly increase hepatic first-pass clearance of Olanzapine; conversely, drugs which inhibit 1A2 activity (examples: Ciprofloxacin, Fluvoxamine) may reduce Olanzapine clearance. The most common side effects appear to be somnolence and weight gain. About 11% of patients gain weight -especially if on a high starting dose and if they were underweight pre-treatment. Sexual dysfunction is a problem for many patients, although sexual dysfunction in schizophrneia does not appear to be primarily attributable to drugs.

Tramadol (sold under the brand name Ultram) is a narcotic analgesic proposed for moderate to severe pain. Tramadol and its O-desmethyl metabolite (M1) are selective, weak OP3-receptor agonists. Opiate receptors are coupled with G-protein receptors and function as both positive and negative regulators of synaptic transmission via G-proteins that activate effector proteins. As the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane, opioids decrease intracellular cAMP by inhibiting adenylate cyclase. Subsequently, the release of nociceptive neurotransmitters such as substance P, GABA, dopamine, acetylcholine, and noradrenaline is inhibited. The analgesic properties of Tramadol can be attributed to norepinephrine and serotonin reuptake blockade in the CNS, which inhibits pain transmission in the spinal cord. The (+) enantiomer has the higher affinity for the OP3 receptor and preferentially inhibits serotonin uptake and enhances serotonin release. The (-) enantiomer preferentially inhibits norepinephrine reuptake by stimulating alpha(2)-adrenergic receptors. Tramadol is used primarily to treat mild-severe pain, both acute and chronic. Its analgesic effects take about one hour to come into effect and 2 h to 4 h to peak after oral administration with an immediate-release formulation. On a dose-by-dose basis, tramadol has about one-tenth the potency of morphine and is approximately equally potent when compared to pethidine and codeine. The most common adverse effects of tramadol include nausea, dizziness, dry mouth, indigestion, abdominal pain, vertigo, vomiting, constipation, drowsiness, and headache. Compared to other opioids, respiratory depression and constipation are considered less of a problem with tramadol.

Metformin is the most widely used drug to treat type 2 diabetes, and is one of only two oral antidiabetic drugs on the World Health Organization (WHO) list of essential medicines. Metformin is an antihyperglycemic agent which improves glucose tolerance in patients with type 2 diabetes, lowering both basal and postprandial plasma glucose. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. However, we still do not completely understand its mechanisms of action. The main effect of this drug from the biguanide family is to acutely decrease hepatic glucose production, mostly through a mild and transient inhibition of the mitochondrial respiratory chain complex I. In addition, the resulting decrease in hepatic energy status activates AMPK (AMP-activated protein kinase), a cellular metabolic sensor, providing a generally accepted mechanism for the action of metformin on hepatic gluconeogenesis. The use of metformin, the most commonly prescribed drug for type 2 diabetes, was repeatedly associated with the decreased risk of the occurrence of various types of cancers, especially of pancreas and colon and hepatocellular carcinoma.

Salmeterol is a long-acting beta2-adrenergic agonist. Although beta2-adrenoceptors are the predominant adrenergic receptors in bronchial smooth muscle and beta1-adrenoceptors are the predominant receptors in the heart, there are also beta2-adrenoceptors in the human heart comprising 10% to 50% of the total beta-adrenoceptors. The precise function of these is not yet established, but they raise the possibility that even highly selective beta2-agonists may have cardiac effects. It is FDA approved for the treatment of asthma, prevention of exercise-induced bronchospasm, maintenance treatment of chronic obstructive pulmonary disease. Common adverse reactions include musculoskeletal pain, headache, influenza, nasal/sinus congestion, pharyngitis, rhinitis, tracheitis/bronchitis, cough, throat irritation, viral respiratory infection. Salmeterol should be administered with extreme caution to patients being treated with monoamine oxidase inhibitors or tricyclic antidepressants, or within 2 weeks of discontinuation of such agents, because the action of salmeterol on the vascular system may be potentiated by these agents. Coadministration of salmeterol and ketoconazole was associated with more frequent increases in QTc duration compared with salmeterol and placebo administration.

Fluvoxamine is an antidepressant which functions pharmacologically as a selective serotonin reuptake inhibitor. Though it is in the same class as other SSRI drugs, it is most often used to treat obsessive-compulsive disorder. Fluvoxamine has been in use in clinical practice since 1983 and has a clinical trial database comprised of approximately 35,000 patients. It was launched in the US in December 1994 and in Japan in June 1999. As of the end of 1995, more than 10 million patients worldwide have been treated with fluvoxamine. The exact mechanism of action of fluvoxamine has not been fully determined, but appears to be linked to its inhibition of CNS neuronal uptake of serotonin. Fluvoxamine blocks the reuptake of serotonin at the serotonin reuptake pump of the neuronal membrane, enhancing the actions of serotonin on 5HT1A autoreceptors. In-vitro studies suggest that fluvoxamine is more potent than clomipramine, fluoxetine, and desipramine as a serotonin-reuptake inhibitor. Studies have also demonstrated that fluvoxamine has virtually no affinity for α1- or α2-adrenergic, β-adrenergic, muscarinic, dopamine D2, histamine H1, GABA-benzodiazepine, opiate, 5-HT1, or 5-HT2 receptors. Fluvoxamine is used for management of depression and for Obsessive Compulsive Disorder (OCD). Has also been used in the management of bulimia nervosa. Fluvoxamine is known under the brand names: Faverin, Fevarin, Floxyfral, Dumyrox and Luvox.

Loratadine is a derivative of azatadine and a second-generation histamine H1 receptor antagonist used in the treatment of allergic rhinitis and urticaria. Unlike most classical antihistamines (histamine H1 antagonists) it lacks central nervous system depressing effects such as drowsiness. Loratadine competes with free histamine and exhibits specific, selective peripheral H1 antagonistic activity. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms (eg. nasal congestion, watery eyes) brought on by histamine. Loratadine has low affinity for cholinergic receptors and does not exhibit any appreciable alpha-adrenergic blocking activity in-vitro. Loratadine also appears to suppress the release of histamine and leukotrienes from animal mast cells, and the release of leukotrienes from human lung fragments, although the clinical importance of this is unknown.

Sumatriptan is a serotonin (5-HT1B/1D) receptor agonist indicated for acute treatment of migraine with or without aura in adults. Sumatriptan is structurally similar to serotonin (5-HT), and is a 5-HT receptor (types 5-HT1D and 5-HT1B) agonist. The specific receptor subtypes it activates are present on the cranial arteries and veins. Acting as an agonist at these receptors, sumatriptan reduces the vascular inflammation associated with migraines. The specific receptor subtype it activates is present in the cranial and basilar arteries. Activation of these receptors causes vasoconstriction of those dilated arteries. Sumatriptan is also shown to decrease the activity of the trigeminal nerve, which presumably accounts for sumatriptan's efficacy in treating cluster headaches. The injectable form of the drug has been shown to abort a cluster headache within 30 minutes in 77% of cases. Sumatriptan is effective for ending or relieving the intensity of migraine and cluster headaches. It is most effective taken early after the start of the pain. Injected sumatriptan is more effective than other formulations. Large doses of sumatriptan can cause sulfhemoglobinemia, a rare condition in which the blood changes from red to greenish-black, due to the integration of sulfur into the hemoglobin molecule. Serious cardiac events, including some that have been fatal, have occurred following the use of sumatriptan injection or tablets. Events reported have included coronary artery vasospasm, transient myocardial ischemia, myocardial infarction, ventricular tachycardia, and ventricular fibrillation (V-Fib).

Ondansetron (ZOFRAN®) is a selective 5-HT3 receptor antagonist. It is effective in the treatment of nausea and vomiting caused by radiotherapy, anesthesia, surgery or cytotoxic chemotherapy drugs, including cisplatin, and has reported anxiolytic and neuroleptic properties. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist. It is not certain whether ondansetron's antiemetic action is mediated centrally, peripherally, or in both sites. However, cytotoxic chemotherapy appears to be associated with release of serotonin from the enterochromaffin cells of the small intestine. The released serotonin may stimulate the vagal afferents through the 5-HT3 receptors and initiate the vomiting reflex.

Felodipine is a long-acting 1,4-dihydropyridine calcium channel blocker (CCB)b. It acts primarily on vascular smooth muscle cells by stabilizing voltage-gated L-type calcium channels in their inactive conformation. By inhibiting the influx of calcium in smooth muscle cells, felodipine prevents calcium-dependent myocyte contraction and vasoconstriction. Felodipine is the most potent CCB in use and is unique in that it exhibits fluorescent activity. In addition to binding to L-type calcium channels, felodipine binds to a number of calcium-binding proteins, exhibits competitive antagonism of the mineralcorticoid receptor, inhibits the activity of calmodulin-dependent cyclic nucleotide phosphodiesterase, and blocks calcium influx through voltage-gated T-type calcium channels. Felodipine is used to treat mild to moderate essential hypertension.