Amoxicillin (Amoxycillin) : Therapeutic uses, Dosage & Side Effects
Amoxicillin is a semisynthetic extended spectrum aminopenicillin antibiotic. It is a close congener of ampicillin (but not a prodrug). It is not resistant to penicillinase or to other β-lactamases. It similar to ampicillin in all respects except: Oral absorption is better; food does not interfere with absorption; higher and more sustained blood levels are produced; Incidence of diarrhoea is lower; It is less active against Shigella and H. influenzae. It is used to treat many different types of infection caused by bacteria, such as tonsillitis, bronchitis, pneumonia, gonorrhea, and infections of the ear, nose, throat, skin, or urinary tract.
Dose : 0.25-1 gm TDS oral/i.m.
Route : Oral, IM, IV
Onset of action : ?
Plasma Half-life : 61.3 minutes
Duration of action : ?
Bioavailability : 95% (oral)
Plasma protein binding : ?
Metabolism : Less than 30% biotransformed in liver
Pregnancy risk category : B
Chemical formula : C16H19N3O5S
IUPAC name : (2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid
Trade name : Amoxylin, Novamox, Synamox, Amoxil, Mox, Moxylong, Moxatag
Antibacterial spectrum : Amoxicillin is active against gram-positive bacteria and many gram-negative bacilli, e.g. H. influenzae, E. coli, Proteus, Salmonella and Shigella. It is active against all organisms sensitive to Penicillin-G(PnG).
- Amoxicillin is more active than PnG for Strep. viridans and enterococci; equally active for pneumococci, gonococci and meningococci (penicillinase resistant strains are resistant to ampicillin as well); but less active against other gram-positive cocci.
- Penicillinase producing Staph. are not affected, as are other gram-negative bacilli, such as Pseudomonas, Klebsiella, indole positive Proteus and anaerobes like Bacteroides fragilis.
Therapeutic uses : Amoxicillin is used for following purposes :
- Ear, Nose, and Throat infections
- Genitourinary tract infections
- Respiratory tract infections including bronchitis, sinusitis, tonsillitis, otitis media, pneumonia, streptococcal pharyngitis etc.
- Meningitis
- Gonorrhoea It is one of the first line drugs for oral treatment of nonpenicillinase producing gonococcal infections.
- Subacute bacterial endocarditis (SABE)
- Skin infections such as acne vulgaris
- Septicaemias and mixed infections
Many physicians now prefer it over ampicillin for bronchitis, urinary infections, SABE and gonorrhoea.
It is also sometimes used together with another antibiotic called clarithromycin to treat stomach ulcers caused by Helicobacter pylori infection.
Amoxicillin is susceptible to degradation by β-lactamase-producing bacteria, which are resistant to most β-lactam antibiotics, such as penicillin. For this reason, Now a days, it is combined with clavulanic acid, a β-lactamase inhibitor. (Amoxiclav)
Mechanism of action : Penicillins interfere with the synthesis of bacterial cell wall.
- The penicillins interfere with the last step of bacterial cell wall synthesis (transpeptidation or cross-linkage), resulting in exposure of the osmotically less stable membrane.
- Cell lysis can then occur, either through osmotic pressure or through the activation of autolysins. These drugs are bactericidal and work in a time-dependent fashion.
Penicillins are only effective against rapidly growing organisms that synthesize a peptidoglycan cell wall. Consequently, they are inactive against organisms devoid of this structure, such as mycobacteria, protozoa, fungi, and viruses.
Side effects : Amoxicillin may cause following adverse reactions :
- Common side effects Nausea, vomiting, diarrhea, rashes, and antibiotic-associated colitis.
- Rarer side effects include mental changes, lightheadedness, anxiety, insomnia, confusion, sensitivity to lights and sounds.
Drug Interactions : Amoxicillin may interact with following drugs :
- Dabigatran
- Methotrexate
- Uricosuric drugs
- Typhoid vaccine
- Probenecid reduces renal excretion and increases the blood levels of amoxicillin
- Warfarin action is increased
- Oral contraceptives may become less effective
- Allopurinol
Contraindications :
- Contraindicated in patients who have experienced a serious hypersensitivity reaction (e.g., anaphylaxis or Stevens-Johnson syndrome) to Amoxicillin or to other β-lactam antibiotics (e.g., penicillins and cephalosporins).
For detailed query or in case of uncertainty, Always consult your doctor or pharmacist.
