Pharmacology- ANTIBIOTICS- PENICILLINS. Rahul Chanshetti Head,Asst.Prof. Department of Pharmacology

Transcription

1 Pharmacology- ANTIBIOTICS- PENICILLINS Rahul Chanshetti Head,Asst.Prof. Department of Pharmacology

2 OBJECTIVES: objectives of study should be achieved by acquiring an in-depth knowledge & thorough understanding, necessary skills and developing the right attitude by following measures a. Adequate knowledge and scientific information regarding basic principles of Pharmacology. b. Pharmacological effects of drugs, list of their adverse effects / reactions, precaution to be taken, contraindications, formulation and route of administrations. c. Consideration of cost, efficiency and safety of medicine according to individual needs. d. Clinical studies for patient counselling leading to physical and social well being of the patients. e. Willing to apply the current knowledge of Pharmacy in the best interest of the patients and the community.

3 An Antibiotic An antibiotic is a selective poison. It has been chosen so that it will kill the desired bacteria, but not the cells in your body. Each different type of antibiotic affects different bacteria in different ways. For example, an antibiotic might inhibit a bacteria's ability to turn glucose into energy, or the bacteria's ability to construct its cell wall. Therefore the bacteria dies instead of reproducing. Substances produced by various species of microorganisms: bacteria, fungi, actinomycetes- to suppress the growth of other microorganisms and to destroy them.

4 History Penicillin was isolated in 1939, and in 1944 Selman Waksman and Albert Schatz, American microbiologists, isolated streptomycin and a number of other antibiotics from Streptomyces griseus.

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6 Penicillins Penicillins contain a b-lactam ring which inhibits the formation of peptidoglycan crosslinks in bacterial cell walls (especially in Grampossitive organisms) Penicillins are bactericidal but can act only on dividing cells They are not toxic to animal cells which have no cell wall

7 Synthesis of Penicillin b-lactams produced by fungi, some ascomycetes, and several actinomycete bacteria b-lactams are synthesized from amino acids valine and cysteine

8 b Lactam Basic Structure

9 Clinical Pharmacokinetics Penicillins are poorly lipid soluble and do not cross the blood-brain barrier in appreciable concentrations unless it is inflamed (so they are effective in meningitis) They are actively excreted unchanged by the kidney, but the dose should be reduced in severe renal failure

10 Resistance This is the result of production of b-lactamase in the bacteria which destroys the b-lactam ring It occurs in e.g. Staphylococcus aureus, Haemophilus influenzae and Neisseria gonorrhoea

11 Examples There are now a wide variety of penicillins, which may be acid labile (i.e. broken down by the stomach acid and so inactive when given orally) or acid stable, or may be narrow or broad spectrum in action

12 Examples Benzylpenicillin (Penicillin G) is acid labile and b-lactamase sensitive and is given only parenterally It is the most potent penicillin but has a relatively narrow spectrum covering Strepptococcus pyogenes, S. pneumoniae, Neisseria meningitis or N. gonorrhoeae, treponemes, Listeria, Actinomycetes, Clostridia

13 Examples Phenoxymethylpenicillin (Penicillin V) is acid stable and is given orally for minor infections it is otherwise similar to benzylpenicillin

14 Examples Ampicillin is less active than benzylpenicillin against Gram-possitive bacteria but has a wider spectrum including (in addition in those above) Strept. faecalis, Haemophilus influenza, and some E. coli, Klebsiella and Proteus strains It is acid stable, is given orally or parenterally, but is b-laclamase sensitive

15 Examples Amoxycillin is similar but better absorbed orally It is sometimes combined with clavulanic acid, which is a b-lactam with little antibacterial effect but which binds strongly to b-lactamase and blocks the action of b-lactamase in this way It extends the spectrum of amoxycillin

16 Examples Flucloxacillin is acid stable and is given orally or parenterally It is b-lactamase resistant It is used as a narrow spectrum drug for Staphylococcus aureus infections

17 Examples Azlocillin is acid labile and is only used parenterally It is b-lactamase sensitive and has a broad spectrum, which includes Pseudomonas aeruginosa and Proteus species It is used intravenously for life-threatening infections,i.e. in immunocompromised patients together with an aminoglycoside

18 Adverse effects Allergy (in 0.7% to 1.0% patients). Patient should be always asked about a history of previous exposure and adverse effects Superinfections(e.g.caused by Candida ) Diarrhoea : especially with ampicillin, less common with amoxycillin Rare: haemolysis, nephritis

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