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Penicillins are the first class of antibacterial medications developed on basis of biologically active substances produced by certain microorganisms. The first penicillins benzylpenicillin was obtained at the beginning of 1940 years.
Penicillins belong to a group of antibiotics called β-lactams (beta-lactams) which also include cephalosporin, carbapenems, monobactams. The similarity of chemical structure predetermine similar action mechanism of all β-lactam namely interfering with synthesis of bacterial cell wall.
Taking into account high clinical effectiveness and low toxicity, β-lactam lactam antibiotics form the bases of antimicrobial chemotherapy and occupy the leading role in the treatment of the majority infections.
Currently the group of penicillins includes more than 20 antibiotics which are divided into several categories:
1.Natural Penicillins (Penicillin G, Procaine, Penicillin G, Penicillin V, Benzathine) The natural penicillins were the first antibiotics introduced in clinical practice. Natural antibiotics are active against gram-positive bacteria such as Streptococcus spp, Staphylococcus spp., Bacillus spp., in less degree against Enterococcus spp.
L.monocytogenes, E.rhusiopathiae and corynebacteria (including C.diphtheriae), the most of anaerobic bacteria (Peptostreptococcus spp., Clostridium spp.) are highly sensitive to natural penicillins. Natural penicillins are highly effective against spirochetes (Treponema, Borrelia, Leptospira).
2.Penicillinase-Resistant Penicillins (Cloxacillin, Dicloxacillin, Methicillin, Nafcillin, Oxacillin). Methicillin was the first member of this group, followed by oxacillin, nafcillin, cloxacillin and dicloxacillin. Currently Oxacillin is the most widespread among penicillinase-resistant penicillins and is actively used for the treatment of infections caused by staphylococci including PRSA.
3.Aminopenicillins (Ampicillin, Amoxicillin, Bacampicillin). Aminopenicillins were the first penicillins discovered to be active against gram-negative bacteria (such as E. coli and H. influenzae). Aminopenicillins are acid-resistant and that is why are administered orally. Aminopenicillins possess a broader spectrum of antibacterial activity against some strains such as E.coli, Shigella spp., Salmonella spp. and P.mirabilis, which are characterized by low levels of production of chromosomal β-lactamase. Aminopenicillins are susceptible to hydrolysis by beta-lactamses and that is why are usually come in combination with beta-lactamse inhibitors.
4.Extended Spectrum Penicillins (sometimes called anti-pseudomonal penicillins). Extended spectrum penicillins include both alpha-carboxypenicillins (carbenicillin and ticarcillin) and acylaminopenicillins (piperacillin, azlocillin, and mezlocillin). These antibiotics possess similar spectrum of antibacterial activity as aminopenicillins but with additional bactericidal activity against the majority of gram negative microorganisms such as Pseudomonas aeruginosa. Along with aminopenicillins, extended spectrum penicillins are inactivated by beta-lactamase. These drugs can be used in monotherapy of infectious diseases or in combination with aminoglycosides.
All beta-lactam antibiotics exert bactericidal action which is associated with inhibition of bacterial cell wall production. Their target is penicillin-depending bacterial proteins which fulfill a function of enzymes on the final stage of peptidoglycan synthesis-biopolymer and the main component of bacterial cell wall. Suppressing of peptidoglycan synthesis leads to consecutive bacterial lysis. Some of penicillin antibiotic exert bacteriostatic effect in low doses which may or may not control the infection
The indications for penicillins vary depending on penicillins group. Natural penicillins are used in:
Infections caused by S.pyogenes, and their consequences:
Infections caused by S.pneumoniae:
Infections caused by other streptococci:
Penicillinase-Resistant Penicillins and namely oxacillin is used in:
Aminopenicillins are indicated for the treatment of:
Carboxypenicillins are usually indicated for the treatment of:
Nosocomial infections caused by sensitive strains P.aeruginosa. Carboxypenicillins must be used only in combination with other antibacterial preparations (aminoglycosides, fluorquinolones). Ticarcillin in combination with clavulonate is indicated in:
Ureidopenicillins usually come in combination with aminoglycosides and are used in the treatment of infections caused by P.aeruginosa
Some of the ureidopenicillis are used against:
Penicillins contraindication. General contraindications include:
Penicillins side effects. Penicillin are considered safe and well-tolerable preparations. The most common side effects include:
Penicillin should not be mixed in one vial with other antibiotics.
There is an increased risk of skin rash in concomitant application with allopurinol.
Potassium-sparing diuretics, ACE inhibitors may increase the risk of hyperpotassemia.
Penicillins should be used with caution in combination with blood thinners and antiplatelets.
Bile-acid sequestrants may bind penicillins in the digestive system and thus decrease their bioavailability.
Oral penicillins may decrease the effectiveness of oral birth control pills.
Penicillin are able to impair the elimination of methotrexate due inhibiting of tubular secretion.