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1、ANTIBIOTICS,M.Raslan,Introduction,*Antibiotic is a natural substance produced by a micro-organism to kill another,ANTIBIOTICS,Classification,*Bacteriostatic (inhibit growth without death) or Bactericidial (Kill) *Mechanism of action *Spectrum of Activity: ( broad or narrow),ANTIBIOTICS,Bacteriostati
2、c vs Bactericidal,*Bacteriostatic: allows for natural immunity to deal with the microbe e.g. Antibodies,phagocytosis *Bactericidial : may lead to release of toxins and microbial contents leading to subsequent illness and inflammatory responses.,ANTIBIOTICS,Spectrum of Activity,*Relates to the number
3、 of microbes that are susceptible to the action of the drug Narrow (limited number) / Broad (wide) *Penicillin G is a narrow spectrum drug as it is only effective against gram-positive microbes. *Tetracyclines are effective against gram-positive and gram-negative microbes (Broad),ANTIBIOTICS,Mechani
4、sm of Action: Inhibition of Cell Wall Synthesis Disruption of Cell Membrane Inhibition of nucleic acid synthesis Inhibition of Protein Synthesis Interference with Metabolic Processes,NB: Bactericidal Bacteriostatic,Inhibition of Cell Wall Synthesis,Example:Penicillins,cephalosporins, vancomycin and
5、bacitracin,ANTIBIOTICS,Disruption of the microbial cell membrane,Affect cell membrane transportation in and out Increases permeability of membrane External influences have greater effect Microbe death Example: Polymyxin, Colistin Note: These agents are more toxic systemically than those agents that
6、inhibit cell wall synthesis.,ANTIBIOTICS,Inhibition of Protein Synthesis,Act either at: * Site of protein synthesis (ribosome) within the nucleus by inhibiting synthesis of nucleic acids *DNA replication / RNA synthesis = TRANSCRIPTION Example: Tetracyclines, aminoglycosides and macrolides (erythrom
7、ycin),ANTIBIOTICS,Interference with metabolic processes,Agents which are structurally similar to para-aminobensoic acid (PABA) a component of folic acid essential for nucleic acid synthesis without it microbes cant produce proteins for growth. Example: sulphonamides weight, age and renal function of
8、 patient. *Some doses (e.g. gentamicin, vancomycin) are determined by therapeutic monitoring of venous blood samples, extracted prior to dosing. Severe infections require intravenous infusion. Observe veins carefully for signs of phlebitis, particularly with penicillins and vancomycin.,ANTIBIOTICS,I
9、ntramuscular injections are painful and avoided, unless essential, in children. A warm compress may reduce pain. N.B. Food affects absorption,ANTIBIOTICS,Table 2. Oral Administration of antibiotics,ANTIBIOTICS,Adverse effects of antibiotics : *Those occurring with all antibiotics *Those restricted t
10、o specific agents,ANTIBIOTICS,Problems Associated with All Antibiotics,ANTIBIOTICS,Table 4. Toxicity associated with antibiotics,Table 4. Toxicity associated with antibiotics,ANTIBIOTICS,ANTIBIOTICS,Contraindications:,1.History of hypersensitivity - Patients allergic to cephalosporins are often alle
11、rgic to penicillins and vice versa. Patients allergic to diuretics or celecoxib or oral hypoglycaemics may be allergic to sulphonamides. 2.Glandular fever (Epstein-Barr virus infection), cytomegalovirus infection greatly increase the risk of developing a penicillin-induced rash.,ANTIBIOTICS,3.Impair
12、ed renal function causes some drugs to accumulate e.g. penicillins, tetracyclines, vancomycin, ciprofloxacin, teicoplanin. 4.Impaired liver function causes some drugs to accumulate e.g. metronidazole, rifampicin. 5.Myasthenia gravis. Aminoglycosides and quinolones exacerbate this condition.,ANTIBIOT
13、ICS,6.Porphyria:Avoid sulphonamides, cephalosporins, erythromycin, flucloxacillin, rifampicin, trimethoprin 7.Pregnancy: Penicillins are usually the antibiotics of first choice. Tetracyclines, trimethoprin, cotrimazole, glycopeptides and aminoglycosides are avoided if possible. 8.Breastfeeding allow
14、s small amounts of antibiotic to pass from mother to infant. Hypersensitivity responses and adverse effects may occur in the infant. Breastfeeding is not advised in some severe infections.,ANTIBIOTICS,Drug Interactions :,1.Adverse effects are cumulative when drugs causing similar problems are co-adm
15、inistered. For example, drugs damaging the inner ear (e.g. gentamicin, vancomycin, teicoplanin, cisplatin, furosemide), are rarely combined 2.Susceptible people suffer an antabuse-like reaction if they take even a small amount of alcohol with certain antibiotics, usually metronidazole or cephamandol
16、e. This results in dilatation of all the blood vessels, causing flushing, severe headache and profound hypotension. Faints, falls and cardiovascular collapse may follow.,ANTIBIOTICS,3.Oral contraceptives Rifampicin and rifabutin render all oral contraceptives ineffective. All broad spectrum antibiot
17、ics increase the risk of pill failure for combined oral contraceptives. 4.Many antibiotics are incompatible with other drugs when co-administered in intravenous infusions. For example, if gentamicin is combined with heparin or a penicillin, its antibiotic activity will be lost.,ANTIBIOTICS,5.Aminoglycosides intensify the action of muscle relaxants such as suxamethonium. Their use must be highlighted when the patient is transferred to the anaesthetic team. 6.Macrolides cause accumulation of other drugs e.g. digoxin, corticosteroids, anti-coagulants.,ANTIBIOTICS,THANK YOU,THANK YOU,ANTIBIOTICS,