Amoxicillin

Amoxicillin (INN), formerly amoxycillin (BAN), amoxycillin (cilamox) in Australia abbreviated Amox,Tormoxin (in India), is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral administration, than other β-lactam antibiotics. It is also a treatment for cystic acne.

Amoxicillin is susceptible to degradation by β-lactamase-producing bacteria, which are resistant to a broad spectrum of β-lactam antibiotics, such as penicillin. For this reason it is often combined with clavulanic acid, a β-lactamase inhibitor, and marketed under one name. This increases effectiveness by reducing its susceptibility to β-lactamase resistance.

Mode of action

Amoxicillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell walls of both Gram-positive and Gram-negative bacteria.

Formulations

Amoxicillin in trihydrate form is available as capsules, chewable and dispersible tablets plus syrup and pediatric suspension for oral use, and as the sodium salt for intravenous administration (although the IV formulation is not available in the United States). It is one of the most common antibiotics prescribed for children, and the liquid forms are helpful where the patient might find it difficult to take tablets or capsules. It has three ionizable groups. A once daily dosing form (Moxatag) was approved by the American FDA in January 2008.

Side effects

Side effects are as those for other beta-lactam antibiotics. Side effects include nausea, vomiting, rashes, and antibiotic-associated colitis. Loose bowel movements (diarrhea) also may occur. Rarer, but patient-reported side effects include mental changes, lightheadedness, confusion, anxiety, sensitivity to lights and sounds and unclear thinking. Immediate medical care is required upon the first signs of these side effects.

The onset of an allergic reaction to amoxicillin can be very sudden and intense - emergency medical attention must be sought as quickly as possible. The initial onset of such a reaction often starts with a change in mental state, skin rash with intense itching (often beginning in fingertips and around groin area and rapidly spreading) and sensations of fever, nausea, and vomiting. Any other symptoms that seem even remotely suspicious must be taken very seriously.

Use of the amoxicillin/clavulanic acid combination for more than one week has caused moderate to severe hepatitis in a number of patients. Young children who ingested acute overdoses of amoxicillin manifested lethargy, vomiting and renal dysfunction.

 Nonallergic amoxicillin rash

Somewhere between 3% to 10% of children taking amoxicillin (or ampicillin) show a late-developing (>72 hours after beginning medication and having never taken penicillin-like medication previously), often itchy rash, which is sometimes referred to as the "amoxicillin rash." The rash can also occur in adults.

The rash is described as maculopapular or morbilliform (measles-like; therefore, in medical literature, it is called "amoxicillin-induced morbilliform rash"). It starts on the trunk and can spread from there. This rash is unlikely to be a true allergic reaction, and is not a contraindication for future amoxicillin usage, nor should the current regimen necessarily be stopped. However, as mentioned above, this common amoxicillin rash and a dangerous allergic reaction cannot easily be distinguished by inexperienced persons, and therefore a health professional should be consulted if a rash develops.

A nonallergic amoxicillin rash may also be an indicator of infectious mononucleosis: Some studies indicate approximately 80-90% of patients with acute Epstein Barr virus infection treated with amoxicillin or ampicillin develop such a rash.

Amoxicillin is one of the semisynthetic penicillins discovered by Beecham scientists. The patent for amoxicillin has expired, thus amoxicillin is marketed under many trade names, including: Actimoxi, Alphamox, Amocla, AMK, Amoksibos, Amoxiclav Sandoz, Amoxidal, Amoxil, Amoxin, Amoksiklav, Amoxibiotic, Amoxicilina, Apo-Amoxi, Augmentin (with clavulanic acid), Bactox, Betalaktam, Cilamox, Curam, Dedoxil, Dispermox, Duomox, E-Mox, Enhancin, Gimalxina, Geramox, Hiconcil, Isimoxin, Klavox, Lamoxy, Moxatag, Moxilen, Moxypen, Moxyvit, Nobactam, Novamoxin, Ospamox, Panklav, Pamoxicillin, Panamox, Polymox, Samthongcillin, Clamoxyl, Senox, Sinacilin, Trimox, Tolodina, Tormoxin (India), Wymox, Yucla, Zerrsox and Zimox.