Erythromycin gastrointestinal infections

Clarithromycin is better absorbed and irritates the gastrointestinal tract less than erythromycin. It is presumed that its activity exceeds that of erythromycin by 2-4 times with respect to a number of streptococci and staphylococci, and to a few other microorganisms. It is used for treating bacterial bronchitis, pneumonia, skin and sexual infections. It is believed that clarithromycin is the most active macrolide for treating atypical mycobacteria. Synonyms of this drug are biaxin and others. 

Clindamycin is a chlorine-substituted derivative of lincomycin. However it is more potent and is better absorbed from the gastrointestinal tract and has therefore replaced lincomycin in most situations. Clindamycin is in principle a bacteriostatic agent. Its indications are mainly limited to mixed anaerobic infections. As mentioned above it has a similar mechanism of action as erythromycin. It selectively inhibits bacterial protein synthesis by binding to the same 50s ribosomal subunits. Erythromycin and clindamycin can interfere with each other by competing for this receptor. Also cross-resistance with erythromycin frequently occurs. Resistance is rather chromosomal rather than plasmid mediated and is especially found in cocci and Clostridium difficile. 

A combination of neomycin and nonabsorbable erythromycin base given orally prior to colorectal surgery can markedly reduce the incidence of postoperative wound infection. Orally administered neomycin is sometimes used to suppress the facultative flora of the gut in patients with hepatic encephalopathy. It is unclear how this improves coma, but one theory is that it reduces systemic absorption of the bacterial metabo-htes that allegedly cause hepatic encephalopathy. Although more than 95% of an oral dose of neomycin is excreted unchanged in the stool of normal subjects, the bioavaUabUity of neomycin may be much higher in patients with an abnormal gastrointestinal mucosa. 

Several antibiotics have been used to treat intestinal protozoal infections. Erythromycin and tetracycline do not have a direct effect on the protozoa they act by altering intestinal bacterial flora and preventing secondary infection. Tetracycline also reduces the normal gastrointestinal bacterial flora on which the amebas depend for growth. 

Erythromycin Prevents bacterial protein synthesis by binding to the 50S ribosomal subunit Bacteriostatic activity against susceptible bacteria Community-acquired pneumonia t pertussis corynebacterial, and chlamydial infections Oral, IV hepatic clearance (half-life 1.5 h) dosed every 6 h cytochrome P450 inhibitor Toxicity Gastrointestinal upset, hepatotoxicity, QTC prolongation... 

Campylobacter species are most commonly responsible for outbreaks of bacterial gastroenteritis in developed countries. The majority of die gastrointestinal Campylobacter infections do not require antibiotic treatment and are selflimiting. Where treatment is required, erythromycin is usually recommended. However, fluoroquinolones are often also used pending laboratory results, because they can cover additional bacterial pathogens and are better tolerated than erythromycin. 

Adverse reactions. Erythromycin is remarkably nontoxic, but the estolate can cause cholestatic hepatitis with abdominal pain and fever which may be confused with viral hepatitis, acute cholecystitis or acute pancreatitis. This is probably an allergy, and recovery is usual but the estolate should not be given to a patient with liver disease. Other allergies are rare. Gastrointestinal disturbances occur frequently (up to 28%), particularly diarrhoea and nausea, but, with the antibacterial spectrum being narrower than with tetracycline, opportunistic infection is less troublesome. 

Azithromycin achieves high concentrations in tissues relative to those in plasma. It remains largely unmetabolised and is excreted in the bile and faeces (t) 50h). Azithromycin is used to treat respiratory tract and soft tissue infections, and sexually transmitted diseases, especially genital Chlamydia infections. Gastrointestinal effects (9%) are less than with erythromycin but diarrhoea, nausea and abdominal pain occur. In view of its high hepatic excretion use in patients with liver disease should be avoided. Interactions see erythromycin (above). 

The macrolide antibiotics include erythromycin, clarithromycin, azithromycin, tylosin, tilmicosin and tiamulin. Clindamycin and lincomycin are related lincosamides. Susceptible bacteria include staphylococci, streptococci, Campylobacter jejunii, Clostridium spp., R. equi, Mycoplasma pneumoniae and Chlamydia spp. Drugs in this group are only effective against a few Gram-negative bacteria in cattle, namely some strains of Pasteurella and Haemophilus spp. Macrolides and lincosamides are associated with causing colitis in horses, so their use is usually restricted to p.o. erythromycin for the treatment of R. equi infections in foals. Subantimicrobial doses of erythromycin are administered i.v. to horses for gastrointestinal prokinetic action. 

Gastrointestinal In 264 (28%) of 942 respondents who took oral erythromycin 1000 mg/ day for 10 days as prophylaxis for pertussis infection, there were some form adverse effects, of which the most common involved gastrointestinal symptoms, for example, diarrhea (16%), stomach ache (7.5%), nausea (3.6%), epigastric distress (2.1%), and abdominal distention (1.8%) [119 ]. 

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