4.1 Antibacterials, Antifungals, And Antiviral Agents Flashcards
Antifungals
Incidents continues to increase, particularly in patients who are required to take immunosuppressive drugs
3 highly effective Antifungal drugs
Amphotericin B
Imidazoles (azoles)
Amphotericin B
- binds to ergosterol combination causes pores to form, resulting in leakage across the fungal membrane.
- A is poorly absorbed from the gastrointestinal tract and must be administered intravenously for systemic fungal disease
- causes a variety of adverse effects, with kidney toxicity being the major dose-limiting toxicity
Imidazoles
- effective when taken orally for systemic fungal infections
- inhibit fungal cytochrome p450 inhibiting ergosterol synthesis
- selective toxicity of the easels lies in their higher affinity for the fungal P450 then the human P450S that are involved in drug metabolism
- Number available as over the counter drugs for the treatment of yeast infections
What step in pharmacokinetics are P450s involved in
Responsible for the metabolism of the vast majority of clinically used drugs
Antivirals
-small infectious agent that is only able to multiply within the living cells of other organisms like plants animals and bacteria
Great need for additional and more effective antiviral drugs
Two drugs for influenza
Amantidine
Oseltamivir
Oseltamivir
Neuraminidase Inhibitor which is an enzyme that allows the spread of the virus from cell to cell drugs of this class prevent neighbouring cells from being infected with the virus
Amantidine
Do you like inhibits the uncoating of viral RNA with an infected cells there by preventing viral infection used due to the influenza a virus
Drug for HSV/VZV
Acyclovir
Taken up into infected cells virus activates drug to the active form
Inhibit viral DNA replication
Long term use well markedly decreased the frequency of reoccurrence of genital herpes
Antibiotics
Purpose is to start bacterial infection by inhibiting the growth and reproduction of bacteria or by directly killing the bacteria
Two ways antibiotics are classified
Narrow spectrum and broad-spectrum
Narrow spectrum
Are only useful against particular species of micro organisms for example penicillin is only effective against gram-positive bacteria
Broad-spectrum
Are effective against a wide range of micro organisms including both gram-positive and gram-negative for example tetracyclines
Types of antibiotics and antibiotic targets
cell wall and cell membrane synthesis
Protein synthesis
Nucleic acid metabolism
Cell wall and membrane synthesis
Two classes of antibiotics penicillin and cephalosporins
Penicillin
Penicillin mould could produce and excrete and antibacterial substance wasn’t successfully isolated from the mould until the Second World War
Penicillin mechanism of action
Closely related to a chemical necessary for the formation of new bacterial cell walls
It interferes with new bacterial cell wall formation and the resulting cells are formed without cell walls
These are known as protoplast and fragile and can readily burst human cells do not have cell walls and are therefore unaffected by penicillin so penicillin to selectively toxic to bacteria
Adverse effects of penicillin
Allergic reaction with an individual is allergic to one penicillin preparation they will be allergic to all penicillin vibrations common manifestations include rash diarrhoea fever face and tongue swelling
Two types of penicillin
Natural - penicillin G
semisynthetic - Penicilin v, methicillin, amphicillin, augmentin
Penicillin G
Extracted and purified from penicillin mould mainly destroys gram-positive bacteria and is useful pneumonia middle year infection skin infections and meningitis also used for the treatment of syphilis
Cephalosporins
Chemically similar to penicillin but in general are more resistant to penicillinase than is the penicillin group
Selective inhibitor’s of bacterial cell wall synthesis
Adverse effects of cephalosporins
Fever and skin rashes renal toxicity may occur in rare cases if allergic to penicillin also allergic to this
Inhibitors of bacterial DNA synthesis
Floroquinolones
Chemically distinct class of anti-micro biles and inhibit bacterial DNA synthesis example of ciprofloxacin can be used for oral or intravenous therapy
Inhibitors of protein synthesis
Three classes of antibiotics tetracyclines, macrolides, and antifolate drugs
Tetracyclines
First broad-spectrum antibiotics developed widespread use for many years many bacteria were formally susceptible to the action have become resistant
Mechanism of action
Tetracycline spine to the 30 S subunit of the mRNA ribosome complex and prevent the addition of amino acids to the protein chain in Hibbett in protein synthesis
Adverse effects
Gastrointestinal effects such as nausea vomiting and diarrhoea
Discolouration of teeth and diminished bone growth tetracyclines have a strong avidity For calcium
If kept for long periods of time they deteriorate into toxic degradation products
Macrolides
Antibiotics are active against several bacterial infections caused by gram-positive microorganisms when organism is allergic to penicillin this is given
Mechanism of action
Buying to the 50 S ribosomal subunits on tRNA and block peptide formation
Adverse effects
Anorexia nausea vomiting and diarrhoea
Antifolate drugs
Inhibitors to fully metabolism and microorganisms
Two antifoliate drugs
Sulfonamides
Trimethoprim
Sulfonamides
Sulphamethoxazole competitively inhibits an upstream step in the synthesis of Tetrahydrofolic acid by inhibiting PABA
Trimethoprim
Inhibits dihydrofolic acid reductase does inhibiting tetrahydrofolic acid formation
Antibiotic resistance
Emergence of resistant strains is a long-standing problem with antibiotics as micro organisms mutate to have different properties and therefore become resistant to antibiotics
Two major factors associated with the development of antibiotic resistance
Evolution and clinical environmental factors
Causes of antibiotic resistance
Physicians over prescribe antibiotics for a number of reasons such as lack of diagnostic equipment or pressure from drug companies and patients
Inappropriate use by patient may result from the patient not finishing their treatment
The use of antibiotics and agriculture may expose the animals to an unnecessary antibiotic which increases the risk of drug resistant development
