Amoxicillin is a bactericidal, broad-spectrum semi-synthetic penicillin which is highly effective against Gram-positive bacteria and many Gram-negative pathogens.
Action
Pharmacology: Amoxicillin is acid-stable since it is not destroyed by the hydrochloric acid of the stomach. The amoxicillin is more rapidly and completely absorbed from the gastrointestinal tract than in ampicillin which is the major difference between the two. Peak concentration in blood are 2 to 21 times greater for amoxicillin than for ampicillin after oral administration of the same dose; they are reached at 2 hours and average about 4 micrograms/mL and 8.5 micrograms/mL when 250 mg and 500 mg, respectively, are administered.
The incidence of diarrhea with amoxicillin is less than that following administration of ampicillin because of more complete absorption. Effective concentrations of orally administered amoxicillin are detectable in the blood for twice as long with ampicillin, again because of the more complete absorption. Like ampicillin, amoxicillin is also low-protein bound since only 20% is attached to albumin in the blood.
Amoxicillin readily diffuses into most body tissues and fluids. Since amoxicillin efficiently penetrates respiratory tissues and secretions. Amoxicillin is most useful in the treatment of various respiratory infections caused by susceptible organisms. Equally significant is its high urinary concentrations where over 60% of the oral antibiotic is excreted unchanged in the kidney. This makes amoxicillin a valuable antibiotic in the treatment of some urinary tract infections.
Amoxicillin produces a bactericidal effect by inhibiting cell wall synthesis, subsequently causing the bacteria to swell, burst and die. Because of the high serum and tissue concentrations obtained with this antibiotic. Amoxicillin provides a bactericidal action that presents the emergence of resistant strains by eliminating first-step mutation. The easy to follow three times a day oral dose regime of amoxicillin for usual infections ensures better patient compliance.
Indications/Uses
Used in the treatment of variety of susceptible infections including biliary-tract infections, bronchitis, endocarditis, gastroenteritis, gonorrhea, mouth infections, otitis media, pneumonia, spleen disorders, typhoid and paratyphoid fever and urinary tract infections.
See Table 1.
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Dosage/Direction for Use
Amoxicillin 250/500 mg capsules one capsule every eight (8) hours, depending upon the type and severity of the infection. Recommended dose may be doubled in moderately severe or severe conditions or as prescribed by the physician.
Amoxicillin suspension: For children weighing less than 20 kg: 20 to 40 mg/kg bodyweight/ day: to be given every 8 hours.
For children weighing more than 20 kg: 250 mg to 500 mg every 8 hours.
Or as prescribed by the physician.
See Table 2.
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Enteric fever: typhoid and paratyphoid: Adults: 4 grams daily in divided doses for 14-21 days.
Children: 100 mg/kg BW/day in divided doses, for 14-21 days.
Typhoid carrier states: 3-4 grams daily in divided doses for a minimum of 1 month.
Gonorrhea: a single dose of 3 grams.
Contraindications
A history of previous hypersensitivity reaction to any of the penicillins is a contraindication.
Special Precautions
As with other antibiotics, occasional overgrowth of nonsusceptible organisms may occur especially during prolonged therapy. Reduced dosage is required in the patients with impaired renal function.
Adverse Reactions
Amoxicillin is comparatively safer and better tolerated since the hepatic, renal and hematopoietic side-effects seen in other broad-spectrum antibiotics are rare. As with other penicillins, it may be expected that untoward reactions are related sensitivity phenomena which include skin rashes and urticaria. Gastrointestinal manifestations may be experienced such as diarrhea, indigestion, glossitis, stomatitis and vomiting.
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