Drugs affecting micro-organisms and parasites. Session 5 Flashcards
What kind of drugs affect micro-organisms and parasites?
antibiotics, anti-fungals, anti-virals, anti-retrovirals
what is the action of antibiotic drugs?
And what drugs target where?
1: inhibition of cell wall synthesis (penicillin, cephalosporins, bacitracin, vancomycin
2: inhibition of protein synthesis (chloramphenicol, erythromycin, tetracyclines, streptomycin
3: inhibition of nucleic acid replication and transcription (quinolones, rifampin)
4: injury to plasma membrane (polymyxin B)
5: inhibition of synthesis of essential metabolites (sulfanilamide, trimethoprim)
Penicillin: What is it used for?
What is its mechanism of action?
infection of ear, nose, throat
bactericidal. weakens cell wall by inhibiting transpeptidase enzymes that cross link peptidoglycan in the cell wall strans, causes cell lysis and death. irreversibly blocks transpeptidase active sites.
Pencillin (beta-lactam ring). adverse effects, contraindications and drug interactions?
GIT upset, candida overgrowth, allergic reactions. Contraindicated in penicillin hypersensitivity. Interacts with the oral contraceptice pill.
erythromycin (macrolides): What is it used for and what is its mechanism of action?
Used for respiratory infection -(useful for pneumonia if mycoplasma are responsible.) Mechanism of action is bacteriostatic, inhibits bacterial RNA-dependent protein synthesis by binding to 50S ribosomal subunit.
Erythromycin: ADR, contraindications and drug interactions?
GIT upset, rash/hypersensitivity reaction, oral/ vaginal thrush. Contraindicated if there is a allergic reaction to macrolides. Interacts with Warfarin.
Amphotericin B is used for what? And what is the mechanism of action?
Amphotericin B is fungicidal and is used for aspergillosus, blastomycosis, candidiasis. It binds to ergosterol in the fungal cell membrane which alters cell permeability and results in a loss of potassium and other elements from the cell.
What is an adverse effect of Amphotericin B?
renal toxicity (80%), hypokalemia (25%). headache, GI distress.
What is tetracycline used for and what is its mechanism of action?
acne (long-term) and for respiratory infections.
Inhibits protein synthesis by reversibly blocking the 30s subunit of the ribosome and preventing access of t-RNA to the m-RNA-ribosome complex.
What is the mechanism of action of co-trimoxazole?
It is structurally similar to PABA (para-aminobenzoic acid) and so competitively inhibits the bacterial enzyme needed to incorporate PABA into dihydrofolic acid-causes a decrease in tetrahydrofolic acid so bacteria cannot synthesise purines and thymidine.
What is co-trimoxazole used for?
ear, nose, throat infections
