Benznidazole is an antiparasitic medication used in first-line treatment of Chagas disease. Benznidazole is a nitroimidazole antiparasitic with good activity against acute infection with Trypanosoma cruzi, commonly referred to as Chagas disease. Like other nitroimidazoles, benznidazole's main mechanism of action is to generate radical species which can damage the parasite's DNA or cellular machinery. Under anaerobic conditions, the nitro group of nitroimidazoles is believed to be reduced by the pyruvate:ferredoxin oxidoreductase complex to create a reactive nitro radical species. The nitro radical can then either engage in other redox reactions directly or spontaneously give rise to a nitrite ion and imidazole radical instead. In mammals, the principal mediators of electron transport are NAD+/NADH and NADP+/NADPH, which have a more positive reduction potential and so will not reduce nitroimidazoles to the radical form. This limits the spectrum of activity of nitroimidazoles so that host cells and DNA are not also damaged. This mechanism has been well-established for 5-nitroimidazoles such as metronidazole, but it is unclear if the same mechanism can be expanded to 2-nitroimidazoles (including benznidazole). In the presence of oxygen, by contrast, any radical nitro compounds produced will be rapidly oxidized by molecular oxygen, yielding the original nitroimidazole compound and a superoxide anion in a process known as "futile cycling". In these cases, the generation of superoxide is believed to give rise to other reactive oxygen species. The degree of toxicity or mutagenicity produced by these oxygen radicals depends on cells' ability to detoxify superoxide radicals and other reactive oxygen species. In mammals, these radicals can be converted safely to hydrogen peroxide, meaning benznidazole has very limited direct toxicity to human cells. In Trypanosoma species, however, there is a reduced capacity to detoxify these radicals, which results in damage to the parasite's cellular machinery. Benznidazole has a significant activity during the acute phase of Chagas disease, with a therapeutical success rate up to 80%. Its curative capabilities during the chronic phase are, however, limited. Some studies have found parasitologic cure (a complete elimination of T. cruzi from the body) in pediatric and young patients during the early stage of the chronic phase, but overall failure rate in chronically infected individuals is typically above 80%. However, some studies indicate treatment with benznidazole during the chronic phase, even if incapable of producing parasitologic cure, because it reduces electrocardiographic changes and a delays worsening of the clinical condition of the patient. Side effects tend to be common and occur more frequently with increased age. The most common adverse reactions associated with benznidazole are allergic dermatitis and peripheral neuropathy. It is reported that up to 30% of people will experience dermatitis when starting treatment. Benznidazole may cause photosensitization of the skin, resulting in rashes. Rashes usually appear within the first 2 weeks of treatment and resolve over time. In rare instances, skin hypersensitivity can result in exfoliative skin eruptions, edema, and fever. Peripheral neuropathy may occur later on in the treatment course and is dose-dependent. Other adverse reactions include anorexia, weight loss, nausea, vomiting, insomnia, and dyslexia, and bone marrow suppression. Gastrointestinal symptoms usually occur during the initial stages of treatment and resolves over time. Bone marrow suppression has been linked to the cumulative dose exposure.

Rilpivirine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) which is used for the treatment of HIV-1 infections in treatment-naive patients. It is active against wild-type and NNRTI-resistant HIV-1. Rilpivirine is a diarylpyrimidinethat inhibits HIV-1 replication by non-competitive inhibition of HIV-1 reverse transcriptase (RT). Rilpivirine does not inhibit the human cellular DNA polymerases α, β and γ.

Fidaxomicin (trade names Dificid, Dificlir in Europe) is the first in a new class of narrow spectrum macrocyclic antibiotic drugs indicated for treatment of Clostridium difficile-associated diarrhea. Lipiarmycin (fidaxomicin), a metabolite of Actinoplanes deccanensis nov. sp. was first isolated in pure form in 1970s and was considered as antibiotic from its chemical and physico-chemical characteristics. It demonstrated high activity against Gram-positive bacteria, including strains resistant to the medically important antibiotics and protected mice experimentally infected with Streptococcus haemolyticus. Fidaxomicin is non-systemic, meaning it is minimally absorbed into the bloodstream, it is bactericidal, and it has demonstrated selective eradication of pathogenic Clostridium difficile with minimal disruption to the multiple species of bacteria that make up the normal, healthy intestinal flora. Although the exact mechanism of action has yet to be fully elucidated, fidaxomicin may bind to and inhibit bacterial DNA-dependent RNA polymerase, thereby inhibiting the initiation of bacterial RNA synthesis. When orally administered, this agent is minimally absorbed into the systemic circulation, acting locally in the gastrointestinal tract. Fidaxomicin appears to be active against pathogenic Gram-positive bacteria, such as clostridia, enterococci, and staphylococci, but does not appear to be active against other beneficial intestinal bacteria. The maintenance of normal physiological conditions in the colon can reduce the probability of Clostridium difficile infection recurrence. It is marketed by Cubist Pharmaceuticals after acquisition of its originating company Optimer Pharmaceuticals.

Artemether is an antimalarial agent used to treat acute uncomplicated malaria. It is administered in combination with lumefantrine for improved efficacy against malaria. Artemether is rapidly metabolized into an active metabolite dihydroartemisinin (DHA). The antimalarial activity of artemether and DHA has been attributed to endoperoxide moiety. Artemethe involves an interaction with ferriprotoporphyrin IX (“heme”), or ferrous ions, in the acidic parasite food vacuole, which results in the generation of cytotoxic radical species. The generally accepted mechanism of action of peroxide antimalarials involves interaction of the peroxide-containing drug with heme, a hemoglobin degradation byproduct, derived from proteolysis of hemoglobin. This interaction is believed to result in the formation of a range of potentially toxic oxygen and carbon-centered radicals. Other mechanisms of action for artemether include their ability to reduce fever by production of signals to hypothalamus thermoregulatory center. Now, recent research has shown the presence of a new, previously unknown cyclooxygenase enzyme COX-3, found in the brain and spinal cord, which is selectively inhibited by artemether, and is distinct from the two already known cyclooxygenase enzymes COX-1 and COX-2. It is now believed that this selective inhibition of the enzyme COX-3 in the brain and spinal cord explains the ability of artemether in relieving pain and reducing fever which is produced by malaria. The most common adverse reactions in adults (>30%) are headache, anorexia, dizziness, asthenia, arthralgia and myalgia.

Besifloxacin (INN/USAN) is a fourth-generation fluoroquinolone antibiotic. The marketed compound is Besifloxacin hydrochloride. It was developed by SSP Co. Ltd., Japan, and designated SS734. SSP licensed U.S. and European rights to SS734 for ophthalmic use to InSite Vision Incorporated in 2000. InSite Vision developed an eye drop formulation (ISV-403) and conducted preliminary clinical trials before selling the product and all rights to Bausch & Lomb in 2003. Besifloxacin is indicated in the treatment of bacterial conjunctivitis caused by sensitive germs, as well as in the prevention of infectious complications in patients undergoing laser therapy for the treatment of cataracts. Besifloxacin inhibits bacterial DNA gyrase and topoisomerase IV and has a broad spectrum of bactericidal activity against strains commonly isolated from patients with bacterial conjunctivitis. In addition, some exploratory in vitro data suggest that Besifloxacin inhibits cytokine formation in human corneal epithelial cells and monocytes, but the relevance of this finding to therapeutic efficacy is unknown.

TELAVANCIN (VIBATIV®) is a lipoglycopeptide antibacterial that is a synthetic derivative of vancomycin. It exerts concentration-dependent, bactericidal activity against Gram-positive organisms in vitro. TELAVANCIN (VIBATIV®) inhibits cell wall biosynthesis by binding to late-stage peptidoglycan precursors, including lipid II. It also binds to the bacterial membrane and disrupts membrane barrier function. TELAVANCIN (VIBATIV®) is indicated for the treatment of adult patients with complicated skin and skin structure infections caused by susceptible isolates of the following Gram-positive microorganisms: Staphylococcus aureus (including methicillin-susceptible and -resistant isolates), Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus anginosus group (includes S. anginosus, S. intermedius, and S. constellatus), or Enterococcus faecalis (vancomycin-susceptible isolates only). It is also indicated for the treatment of adult patients with hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP), caused by susceptible isolates of Staphylococcus aureus (both methicillin-susceptible and -resistant isolates). It should be reserved for use when alternative treatments are not suitable.

Etravirine (formerly known as TMC125) is an antiretroviral agent more specifically classified as a Non-Nucleoside Reverse Transcriptase Inhibitor. Etravirine exerts its effects via direct inhibition of the reverse transcriptase enzyme of human immunodeficiency virus type 1 (HIV-1). It directly binds reverse transcriptase and consequently blocks DNA-dependent and RNA-dependent polymerase activity. In combination with other antiretroviral agents, it is indicated for the treatment of human immunodeficiency virus type 1 (HIV-1) infection in antiretroviral treatment-experienced adult patients, who have evidence of viral replication and HIV-1 strains resistant to a non-nucleoside reverse transcriptase inhibitor (NNRTI) and other antiretroviral agents. The most common adverse events (incidence > 10%) of any intensity that occurred at a higher rate than placebo are rash and nausea. Etravirine should not be co-administered with the following antiretrovirals: Tipranavir/ritonavir, fosamprenavir/ritonavir, atazanavir/ritonavir; Protease inhibitors administered without ritonavir; NNRTIs.

Raltegravir (RAL, Isentress, formerly MK-0518) is an antiretroviral drug produced by Merck & Co., used to treat HIV and it is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in patients 4 weeks of age and older. Raltegravir inhibits the catalytic activity of HIV-1 integrase, an HIV-1 encoded enzyme that is required r viral replication. Inhibition of integrase prevents the covalent insertion, or integration, of unintegrated linear HIV-1 DNA into the host cell genome preventing the formation of the HIV-1 provirus. The provirus is required to direct the production of progeny virus, so inhibiting integration prevents propagation of the viral infection. Raltegravir did not significantly inhibit human phosphoryl transferases including DNA polymerases α, β, and γ. Coadministration with others drugs that are strong inducers of UGT1A1, such as rifampin, may result in reduced plasma concentrations of raltegravir. The most common adverse reactions of moderate to severe intensity (≥2%) are insomnia, headache, dizziness, nausea and fatigue. Severe, potentially life-threatening, and fatal skin reactions have been reported. This include cases of Stevens-Johnson syndrome and toxic epidermal necrolysis. Hypersensitivity reactions have also been reported and were characterized by rash, constitutional findings, and sometimes, organ dysfunction, including hepatic failure. The major mechanism of clearance of raltegravir in humans is UGT1A1-mediated glucuronidation.

Retapamulin is a topical antibiotic which was approved by FDA (Altabax brand name) for the treatment of impetigo due to Staphylococcus aureus (methicillin-susceptible isolates only) or Streptococcus pyogenes. Retapamulin exerts its antibacterial action by binding to 50S subunit of the bacterial ribosome.

Maraviroc (UK-427,857; brand-named Selzentry, or Celsentri outside the U.S) is a selective CCR5 antagonist with potent anti-human immunodeficiency virus type 1 (HIV-1) activity and favorable pharmacological properties. Maraviroc is the product of a medicinal chemistry effort initiated following identification of an imidazopyridine CCR5 ligand from a high-throughput screen of the Pfizer compound file. Selzentry, in combination with other antiretroviral agents, is indicated for adult patients infected with only CCR5-tropic HIV-1. This indication is based on analyses of plasma HIV-1 RNA levels in two controlled trials of SELZENTRY in treatment-experienced subjects and one trial in treatment-naive subjects. Maraviroc selectively binds to the human chemokine receptor CCR5 present on the cell membrane, preventing the interaction of HIV-1 gp120 and CCR5 necessary for CCR5-tropic HIV-1 to enter cells. CXCR4-tropic and dual-tropic HIV-1 entry is not inhibited by maraviroc. Antiviral Activity in Cell Culture Maraviroc inhibits the replication of CCR5-tropic laboratory strains and primary isolates of HIV-1 in models of acute peripheral blood leukocyte infection. The mean EC50 value (50% effective concentration) for maraviroc against HIV-1 group M isolates (subtypes A to J and circulating recombinant form AE) and group O isolates ranged from 0.1 to 4.5 nM (0.05 to 2.3 ng per mL) in cell culture. When used with other antiretroviral agents in cell culture, the combination of maraviroc was not antagonistic with NNRTIs (delavirdine, efavirenz, and nevirapine), NRTIs (abacavir, didanosine, emtricitabine, lamivudine, stavudine, tenofovir, zalcitabine, and zidovudine), or protease inhibitors (amprenavir, atazanavir, darunavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, and tipranavir). Maraviroc was not antagonistic with the HIV fusion inhibitor enfuvirtide. Maraviroc was not active against CXCR4-tropic and dual-tropic viruses (EC50 value greater than 10 µM). The antiviral activity of maraviroc against HIV-2 has not been evaluated. Maraviroc can cause serious, life-threatening side effects such as, liver problems, skin reactions, and allergic reactions.