Amoxicillin
AMOXICILLIN
- Close congener of ampicillin (but not a prodrug).
- Component of most triple drug H. pylori eradication regimens.
- More active against penicillin-resistant Strep. pneumoniae.
- It is less active against Shigella and H. influenzae.
PHARMACOKINETICS:
Absorption:
- Rapidly and well absorbed from GI tract.
- Bioavailability: Approx 70%.
- Time to peak plasma concentration: Within 1-2.5 hr.
Distribution:
- It crosses placental barrier
- Pregnancy: Category B
- Enters breast milk (small amounts)
- Readily distributes into most body tissues & fluid.
- Except into cerebrospinal fluid.
- Volume of distribution: Approx 0.3-0.4 L/kg (amoxicillin); approx 0.2 L/kg (clavulanic acid).
- Plasma protein binding: Approx 18% (amoxicillin); approx 25% (clavulanic acid).
Excretion:
- Via urine (amoxicillin: Approx 50-70 %; clavulanic acid: Approx 25-40%) as drug unchanged during 1st 6 hr after administration.
- Mean elimination half-life: Approx 1 hr.
DOSAGE:
- Gonorrhoea (including PPNG) –
- Single-dose amoxicillin 3 g + clavulanic acid 0.5 g + probenecid 1 g.
INDICATIONS:
- Respiratory tract infection
- Melioidosis
- Infected animal bites
- Susceptible infections
- Dental abscesses
- Used in H. pylori
- Acute uncomplicated 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 & hepatic impairment.
- Children
- Pregnancy and lactation.
- Monitoring Parameters: Periodically monitor renal, hepatic and hematologic function.
- Monitor for signs of anaphylaxis during 1st dose.
ADVERSE DRUG REACTIONS:
- Diarrhoea/loose stools, Clostridium difficle -associated diarrhoea
- Incidence of diarrhoea 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.
- The incidence of diarrhoea is lower.
- Food does not interfere with its absorption.
Don’t Forget to Solve all the previous Year Question asked on Amoxicillin
