Ganciclovir is a synthetic acyclic nucleoside analogue of 2'-deoxyguanosine active against cytomegalovirus. Ganciclovir has been shown to be active against cytomegalovirus (CMV) and herpes simplex virus (HSV) in humans. To achieve anti-CMV activity, ganciclovir is phosphorylated first to the monophosphate form by a CMV-encoded (UL97 gene) protein kinase homologue, then to the di- and triphosphate forms by cellular kinases. Ganciclovir triphosphate concentrations may be 100-fold greater in CMV-infected than in uninfected cells, indicating preferential phosphorylation in infected cells. Ganciclovir triphosphate, once formed, persists for days in the CMV-infected cell. Ganciclovir triphosphate is believed to inhibit viral DNA synthesis by (1) competitive inhibition of viral DNA polymerases; and (2) incorporation into viral DNA, resulting in eventual termination of viral DNA elongation. Ganciclovir is indicated for the treatment of CMV retinitis in immunocompromised patients, including patients with acquired immunodeficiency syndrome (AIDS) and for the treatment of acute herpetic keratitis.

Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Zidovudine is phosphorylated to active metabolites that compete for incorporation into viral DNA. They inhibit the HIV reverse transcriptase enzyme competitively and act as a chain terminator of DNA synthesis. The lack of a 3'-OH group in the incorporated nucleoside analogue prevents the formation of the 5' to 3' phosphodiester linkage essential for DNA chain elongation, and therefore, the viral DNA growth is terminated. Zidovudine, a structural analog of thymidine, is a prodrug that must be phosphorylated to its active 5′-triphosphate metabolite, zidovudine triphosphate (ZDV-TP). It inhibits the activity of HIV-1 reverse transcriptase (RT) via DNA chain termination after incorporation of the nucleotide analogue. It competes with the natural substrate dGTP and incorporates itself into viral DNA. It is also a weak inhibitor of cellular DNA polymerase α and γ. Zidovudine is used in combination with other antiretroviral agents for the treatment of human immunovirus (HIV) infections. Zidovudine is marketed as Retrovir.

Ribavirin is a synthetic nucleoside analogue, which was first discovered and developed in 1970 by researchers from the International Chemical & Nuclear Corporation (ICN), today known as Valeant Pharmaceuticals. Ribavirin was initially approved for use in humans to treat pediatric respiratory syncytial virus infections (RSV). In cell cultures the inhibitory activity of ribavirin for RSV is selective. The mechanism of action is unknown. Reversal of the in vitro antiviral activity by guanosine or xanthosine suggests ribavirin may act as an analogue of these cellular metabolites. There were no other significant advancements in the treatment of hepatitis C until 1998, when the combination of ribavirin and interferon-alpha gained approval. Clinically, ribavirin showed a small, additive antiviral effect in combination with interferon, but its main effect was dose-dependent prevention of virological relapse. The mechanism by which the combination of ribavirin and an interferon product exerts its effects against the hepatitis C virus has not been fully established. However, it could be thorough the inhibition of inosine monophosphate dehydrogenase (IMPDH), which is the key step in de novo guanine synthesis, a requirement for viral replication.

Cyclosporins are cyclic polypeptide macrolides that were originally derived from the soil fungus Tolypocladium inflatum. Cyclosporine (also known as cyclosporine A) was discovered by Sandoz and developed for the tretment of immune disorders. The drug was approved by FDA for such diseases as Rheumatoid Arthritis, Psoriasis (Neoral), Keratoconjunctivitis sicca (Restasis) and prevention of transplant rejections (Neoral and Sandimmune). Cyclosporine’s primary immunosuppressive mechanism of action is inhibition of T-lymphocyte function. Upon administration cyclosporine binds to cyclophilin A and thus inhibits calcineurin, leading to immune system suppression.

Oxybutynin is an antispasmodic, anticholinergic agent indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency. Oxybutynin relaxes bladder smooth muscle. Oxybutynin exhibits only one-fifth of the anticholinergic activity of atropine on the rabbit detrusor muscle, but four to ten times the antispasmodic activity. Antimuscarinic activity resides predominantly in the R-isomer. Oxybutynin exerts a direct antispasmodic effect on smooth muscle and inhibits the muscarinic action of acetylcholine on smooth muscle. No blocking effects occur at skeletal neuromuscular junctions or autonomic ganglia (antinicotinic effects). By inhibiting particularily the M1 and M2 receptors of the bladder, detrusor activity is markedly decreased.

Tobramycin, an aminoglycoside antibiotic obtained from cultures of Streptomyces tenebrarius, it is effective against gram-negative bacteria, especially the pseudomonas species. Tobramycin is used in combination with other antibiotics to treat urinary tract infections, gynecologic infections, peritonitis, endocarditis, pneumonia, bacteremia and sepsis, respiratory infections including those associated with cystic fibrosis, osteomyelitis, and diabetic foot and other soft-tissue infections. It acts primarily by disrupting protein synthesis, leading to altered cell membrane permeability, progressive disruption of the cell envelope, and eventual cell death. Tobramycin has in vitro activity against a wide range of gram-negative organisms including Pseudomonas aeruginosa. Tobramycin binds irreversibly to one of two aminoglycoside binding sites on the 30 S ribosomal subunit, inhibiting bacterial protein synthesis. Tobramycin may also destabilize bacterial memebrane by binding to 16 S 16 S r-RNA. An active transport mechanism for aminoglycoside uptake is necessary in the bacteria in order to attain a significant intracellular concentration of tobramycin. KITABIS PAK (co-packaging of tobramycin inhalation solution and PARI LC PLUS Reusable Nebulizer) is indicated for the management of cystic fibrosis in adults and pediatric patients 6 years of age and older with P. aeruginosa.

Ibuprofen is a nonsteroidal anti-inflammatory agent (NSAIA) or nonsteroidal anti-inflammatory drug (NSAID), with analgesic and antipyretic properties. Ibuprofen has pharmacologic actions similar to those of other prototypical NSAIAs, which are thought to act through inhibition of prostaglandin synthesis. It’s used temporarily relieves minor aches and pains due to: headache; the common cold; muscular aches; backache; toothache; minor pain of arthritis; menstrual cramps and temporarily reduces fever. The exact mechanism of action of ibuprofen is unknown. Ibuprofen is a non-selective inhibitor of cyclooxygenase, an enzyme invovled in prostaglandin synthesis via the arachidonic acid pathway. Its pharmacological effects are believed to be due to inhibition cylooxygenase-2 (COX-2) which decreases the synthesis of prostaglandins involved in mediating inflammation, pain, fever and swelling. Antipyretic effects may be due to action on the hypothalamus, resulting in an increased peripheral blood flow, vasodilation, and subsequent heat dissipation. Inhibition of COX-1 is thought to cause some of the side effects of ibuprofen including GI ulceration. Ibuprofen is administered as a racemic mixture. The R-enantiomer undergoes extensive interconversion to the S-enantiomer in vivo. The S-enantiomer is believed to be the more pharmacologically active enantiomer.

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.

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.