Amoxicillin

PHARMACOKINETICS
  • Absorption:
  1. Rapidly and well absorbed from GI tract. Bioavailability: Approx 70%. Time to peak plasma concentration: W/in 1-2.5 hr.
  • Distribution: 
  1. It crosses the placental barrier(category B); enters breast milk (small amounts); readily distributes into most body tissues and fluid.
  2. Amoxicillin: Readily distributes except into cerebrospinal fluid.
  3. Volume of distribution: Approx 0.3-0.4 L/kg (amoxicillin); approx 0.2 L/kg (clavulanic acid). 
  4. Plasma protein binding: Approx 18% (amoxicillin); approx 25% (clavulanic acid).
  • Excretion: 
  1. Via urine (amoxicillin: Approx 50-70% ; clavulanic acid: Approx 25-40%) as unchanged drug during the 1st 6 hr after admininistration. 
  2. Mean elimination half-life: Approx 1 hr.
INDICATIONS:
  • Respiratory tract infection,
  • Melioidosis;
  • Infected animal bites;
  • Susceptible infections 
  • Dental abscesses
  • used in H. pylori
  • Acuteuncomplicated urinary tract infections
  • Severe or recurrent respiratory tract infections
  • Prophylaxis of endocarditis
  • Pharyngitis ; Tonsillitis
  • Susceptible infections
  • Prophylaxis of surgical infections
  • Drug-induced liver injury.
CONTRAINDICATION :
  • Hypersensitivity to penicillins.
  • History of severe immediate hypersensitivity reaction to another β-lactam agent (e.g. cephalosporins, carbapenem or monobactam),
  • History of cholestatic jaundice/hepatic dysfunction associated w/ amoxicillin and clavulanic acid therapy.
PRECAUTION:
  • Renal and hepatic impairment.
  • Children
  • Pregnancy and lactation. 
  • Monitoring Parameters : Periodically monitor renal, hepatic and haematologic function.
  • Monitor for signs of anaphylaxis during 1st dose.
ADVERSE DRUG REACTIONS:
  • Diarrhoea/loose stools, Clostridium difficile-associated diarrhoea(Incidence of diarrhea is lower than ampicillin),
  • Pseudomembranous colitis,
  • Nausea, vomiting, 
  • Skin rashes, urticaria, vaginitis
  • Potentially Fatal: Anaphylaxis, Stevens-Johnson syndrome.
DRUG INTERACTIONS:
  • May increase plasma concentration of amoxicillin w/ probenecid.
  • May increase allergic or hypersensitivity reaction w/ concomitant use of allopurinol and amoxicillin.
  • May reduce efficacy of oral oestrogen/progesterone contraceptives.
Exam Question
  • Amoxicillin is used in H. pylori
  • The MOST frequently implicated antibiotic among the causes of DILI is Amoxicillin -clavulanic acid
  • The most frequently implicated antibiotic among the causes of drug induced liver injury is Amoxicillin-clavulanic acid
  • Drug of choice for prevention of infection by animal bite Amoxicillin/clavulanate
  • Moraxella catarrhalis is resistant to Amoxicillin
  • Advantages of amoxicillin over ampicillin are Better bioavailability & faster action, Incidence of diarrhea is lower, Food does not interfere with its absorption
Don't Forget to Solve all the previous Year Question asked on Amoxicillin