Амоксициллин

solid

Antibacterial;Bacterial transpeptidase inhibitor

Amoxycillin, like ampicillin, has a broad spectrum of use. Indications for use are the same as with ampicillin. Synonyms of this drug are amoxican, amoxil, larotid, robamox, trimox, vimox, utimox, and others. Undoubtedly, analogs of ampicillin that are substituted at the amine fragment of phenylglycine (azolcillin, mezlocillin, piperacillin) should be included in this same group of compounds.

ChEBI: A penicillin in which the substituent at position 6 of the penam ring is a 2-amino-2-(4-hydroxyphenyl)acetamido group.

The antibacterial spectrum is identical to that of ampicillin and there are few differences in antibacterial activity . Like ampicillin, amoxicillin is unstable to most β-lactamases. It has useful activity against Helicobacter pylori (<1% resistance), and is included in most combination regimens for the treatment of H. pylori infections.

There is complete cross-resistance with ampicillin. Its action against many β-lactamase-producing strains can be restored by co-administration with β-lactamase inhibitors.

Amoxicillin is both a topical and a systemic sensitizer. Topical sensitization occurs in health care workers. Systemic drug reactions are frequent, such as urticaria, maculo-papular rashes, baboon syndrome, acute generalized exanthematous pustulosis, or even toxic epidermal necrosis. Cross-reactivity is common with ampicillin, and can occur with other penicillins.

Amoxicillin shows a bactericidal (kills microorganisms) effect against susceptible organisms (bacteria that are unable to grow in the presence of the drug) during their stage of active multiplication. Amoxicillin mode of action is similar to ampicillin, and thus it works by preventing the synthesis of the mucopeptide (a protein responsible for the growth of bacteria) present in the cell wall, which in turn leads to the death of the bacteria.

Oral absorption: 75–90%
C_max 500 mg oral: 5.5–7.6 mg/L after 1–2 h
500 mg intramuscular: c. 14 mg/L after 1–2 h
Plasma half-life: 1 h
Volume of distribution: 0.3 L/kg
Plasma protein binding: 17–20%
Absorption and distribution
Oral absorption produces over twice the peak concentration achieved by comparable doses of ampicillin, allowing less frequent dosing intervals. Absorption is unaffected by food. It is well-distributed in multiple body fluids, including pleural, peritoneal and middle ear fluid. It does not penetrate well into the CSF.
Metabolism and excretion
Some 10–25% is converted to the penicilloic acid. Between 50% and 70% of unchanged drug is recovered in the urine in the first 6 h after a dose of 250 mg. Plasma levels are elevated and prolonged by the administration of probenecid.

Amoxicillin, 6-[D-(－)-α-amino-p- hydroxyphenylacetamido]penicillanic acid (Amoxil, Larotid, Polymox), a semisyntheticpenicillin introduced in 1974, is simply the p-hydroxyanalog of ampicillin, prepared by acylation of 6-APA with phydroxyphenylglycine.Its antibacterial spectrum is nearly identical with that ofampicillin, and like ampicillin, it is resistant to acid, susceptibleto alkaline and β-lactamase hydrolysis, andweakly protein bound. Early clinical reports indicated thatorally administered amoxicillin possesses significantadvantages over ampicillin, including more complete GIabsorption to give higher plasma and urine levels, lessdiarrhea, and little or no effect of food on absorption.50Thus, amoxicillin has largely replaced ampicillin for thetreatment of certain systemic and urinary tract infectionsfor which oral administration is desirable. Amoxicillin isreportedly less effective than ampicillin in the treatment ofbacillary dysentery, presumably because of its greater GIabsorption. Considerable evidence suggests that oral absorptionof α-aminobenzyl–substituted penicillins (e.g.,ampicillin and amoxicillin) and cephalosporins is, at leastin part, carrier mediated, thus explaining their generallysuperior oral activity.Amoxicillin is a fine, white to off-white, crystallinepowder that is sparingly soluble in water. It is available invarious oral dosage forms. Aqueous suspensions are stablefor 1 week at room temperature.

Amoxicillin is generally well tolerated, side effects being those common to penicillins, but including non-allergic rashes in patients with glandular fever. As the drug is well absorbed, diarrhea is generally infrequent and rarely sufficiently severe to require withdrawal of treatment. Common side effects of Amoxicillin include Diarrhoea (loose stools), Headache, Nausea (vomiting sensation), Vomiting, Rash, Anaphylaxis (allergic condition), and Anaemia (lack of blood). Serious side effects of Amoxicillin include Thrombocytopenia (deficiency of platelets), Convulsions (involuntary movements of body muscles), Cholestatic jaundice (jaundice caused due to the stoppage of bile from the liver), Meningitis (inflammation of brain and spinal membranes), and Vasculitis (inflammation of blood vessels).