Chemotherapy Flashcards
D-cycloserine
Structural analogue of D-Ala; prevents the synthesis of
pentapeptide by inhibiting L-Ala racemase, D-Ala-D-Ala synthetase and D-Ala-DAla/muramyl tripeptide ligase
Fosfomycin
Inhibits pyruvyl transferase required for the conversion of NAG into NAM. Was recently approved in the USA for treatment of urinary tract infections
Bacitracin
Cyclic polypeptide antibiotic; forms a tight complex with Mg2+ and bactoprenol pyrophosphate; inhibits the dephosphorylation to bactoprenol phosphate (lipid carrier for NAM-NAG unit). It is active against Gram-positive bacteria
Penicillin, Ampicillin, Amoxicillin, and Methicillin
ß-lactam antibiotics; inhibit peptidoglycan-crosslinking transpeptidase enzymes by covalent and irreversible binding as a pseudosubstrate. The combination of the ß-lactam amoxicilin and the ß-lactamase inhibitor clavulanate is used as augmentin
Vancomycin
Glycopeptide antibiotic; binds
to D-Ala-D-Ala termini of the pentapeptide in peptidoglycan, thereby preventing its cross-linking to a neighbouring pentapeptide in another peptidoglycan strand. Vancomycin is effective against Clostridium difficile, and is used intravenously against Gram-positive cocci, such as Enterococcus and Staphylococcus
Isoniazid
Isoniazid is a first-line medication used in the prevention and treatment of tuberculosis. It inhibits the biosynthesis of mycolic acids in the cell envelope of Mycobacterium tuberculosis
Chloramphenicol
Blocks aminoacyl tRNA binding to 50S subunit of ribosome. Very effective broad-spectrum antibiotic but use is restricted because of bone marrow suppression in some cases. Drug is indicated in life-threatening infections such as meningitis.
Tetracycline
Polyketide antibiotic; binds to 16 rRNA in 30S subunit of ribosome and inhibits the movement of aminoacyl-tRNA into the A site. Tetracyclines are effective against a wide range of bacteria, and are first-line drugs against 72 mycoplasma and cholera. Drug toxicity is associated with binding of calcium in bones and teeth.
Erythromycin
14-membered macrolide antibiotic; binds to 23S rRNA in 50S subunit, and blocks the polypeptide exit tunnel. Drug has a similar antibacterial spectrum as penicillin, and is a suitable second-line drug for patients allergic to penicillin.
Fusidic acid
Inhibits elongation factor G, and hence, the movement of the 30S subunit by one codon along the mRNA. Drug has narrow spectrum, and is used against staphylococcal infections
Streptomycin and gentamycin
Aminoglycoside antibiotics; target 30S subunit of ribosome and decrease fidelity of mRNA translation. Streptomycin exhibits nephrotoxicity and ototoxicity. These effects are reduced for gentamycin. Used against Gram-negative rods including Pseudomonas and Proteus. Most streptococci
(Gram-positive) are resistant because gentamycin cannot penetrate the cell. However, penicillin and gentamycin have a synergistic effect against some streptococci.
Ciprofloxacin
Fluoroquinolone antibiotic; inhibits type II DNA topoisomerases (DNA gyrase and topo IV), and hence, inhibits changes in supercoiling required for replication and gene expression. Ciprofloxacin is an FDAapproved drug for killing Bacillus anthracis in anthrax infections. It is particularly useful for Pseudomonas infections where oral therapy is preferred, such as respiratory tract infections in patients with cystic fibrosis.
Rifampin
Binds to β subunit of the DNA-dependent RNA polymerase, and inhibits initiation of RNA synthesis. Is often used to treat infections by Mycobacterium
Daunomycin
Planar polycyclic anthracycline antibiotic; intercalates in dsDNA and causes local unwinding. Used as anticancer agent.
Bleomycin
Metal-chelating glycopeptide antibiotic; generates superoxide and hydroxyl radicals, causing single- and double-strand breaks in DNA.
Mitomycin C
Aziridine-containing antibiotic; alkylates and cross-links DNA, thereby preventing strand separation during DNA replication and transcription. Antibiotics that act as antimetabolites
Sulfamethoxazole
Sulfa drug; p-aminobenzoate analogue that competitively inhibits dihydropteroate synthase in the biosynthesis of tetrahydrofolate (methyl carrier required for synthesis of dTMP).
Trimethoprim
Dihydrofolate reductase in the biosynthesis of tetrahydrofolate
Co-trimoxazole
Combination of sulfamethoxazole and trimethoprim. Cotrimoxazole has been withdrawn as a routine anti-bacterial agent in this country, as result of its being implicated in cases of Stevens-Johnson syndrome – a severe and sometimes fatal allergic reaction. Co-trimoxazole is used in AIDS patients with fungal Pneumocystis carinii infections.
Valinomycin
Cyclic peptide antibiotic that binds K+, and facilitates K+ diffusion across the membrane.
Gramicidin A
Linear polypeptide antibiotic; forms a homodimeric complex that acts as an ion channel in the membrane.
Polymixin
Cationic detergent antibiotic containing cyclic peptide and hydrophobic tail; binds to membrane and alters its ion permeability.
Amphotericin B
Polyene antifungal and antiparasitic drug; forms pores in the membrane by an ergosterol-dependent mechanism. Is currently the drug of choice for most systemic mycoses: active against Cryptococcus, Candida, and Aspergillus.
Fluconazole
Triazole antifungal drug. Fluconazole is often used in the treatment of athlete’s foot and vaginal candidiasis. Inhibits ergosterol synthesis
Miconazole
Imidazole antifungal and antiprotozoal drug. Inhibit ergosterol biosynthesis. antiprotozoal drugs
Melarsen
Arsenic compound; selectively accumulated in Trypanosoma species, inhibits energy metabolism. Used for treatment of human sleeping sickness and other diseases caused by trypanosomes.