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.