Amoxicillin was discovered in 1958 and came into medical use in 1972.[11][12] Amoxil was approved for medical use in the United States in 1974,[4][5] and in the United Kingdom in 1977.[2] It is on the (WHO)
World Health Organization's List of Essential Medicines.[13][14] It is one of the most commonly prescribed antibiotics in children.[15] Amoxicillin is available as a
generic medication.[8] In 2021, it was the 38th most commonly prescribed medication in the United States, with more than 16million prescriptions.[16][17]
Children with acute otitis media who are younger than six months of age are generally treated with amoxicillin or other antibiotics. Although most children with acute otitis media who are older than two years old do not benefit from treatment with amoxicillin or other antibiotics, such treatment may be helpful in children younger than two years old with acute otitis media that is bilateral or accompanied by ear drainage.[19] In the past, amoxicillin was dosed three times daily when used to treat acute otitis media, which resulted in missed doses in routine
ambulatory practice. There is now evidence that two times daily dosing or once daily dosing has similar effectiveness.[20]
Respiratory infections
Most sinusitis infections are caused by
viruses, for which amoxicillin and amoxicillin-clavulanate are ineffective,[21] and the small benefit gained by amoxicillin may be overridden by the adverse effects.[22]
Amoxicillin is considered the first-line
empirical treatment for most cases of uncomplicated bacterial sinusitis in children and adults when culture data is unavailable.[23][24][25] Amoxicillin is recommended as the preferred first-line treatment for
community-acquired pneumonia in adults by the
National Institute for Health and Care Excellence, either alone (mild to moderate severity disease) or in combination with a
macrolide.[26] The
World Health Organization (WHO) recommends amoxicillin as first-line treatment for pneumonia that is not "severe".[27] Amoxicillin is used in post-exposure inhalation of
anthrax to prevent disease progression and for prophylaxis.[18]
Amoxicillin is effective for treatment of early cutaneous
Lyme borreliosis; the effectiveness and safety of oral amoxicillin is neither better nor worse than common alternatively-used antibiotics.[29]
Amoxicillin is occasionally used for the treatment of skin infections,[18] such as
acne vulgaris.[31] It is often an effective treatment for cases of acne vulgaris that have responded poorly to other antibiotics, such as
doxycycline and
minocycline.[32]
Infections in infants in resource-limited settings
Amoxicillin is recommended by the World Health Organization for the treatment of
infants with signs and symptoms of pneumonia in resource-limited situations when the parents are unable or unwilling to accept
hospitalization of the child. Amoxicillin in combination with
gentamicin is recommended for the treatment of infants with signs of other severe infections when hospitalization is not an option.[33]
Prevention of bacterial endocarditis
It is also used to prevent
bacterial endocarditis and as a pain-reliever in high-risk people having dental work done, to prevent Streptococcus pneumoniae and other
encapsulated bacterial infections in those without
spleens, such as people with
sickle-cell disease, and for both the prevention and the treatment of
anthrax.[8] The United Kingdom recommends against its use for infectious endocarditis prophylaxis.[34] These recommendations do not appear to have changed the rates of infection for infectious endocarditis.[35]
Adverse effects are similar to those for other
β-lactam antibiotics, including
nausea, vomiting, rashes, and antibiotic-associated
colitis. Loose bowel movements (diarrhea) may also occur. Rarer adverse effects include mental changes, lightheadedness, insomnia, confusion, anxiety, sensitivity to lights and sounds, and unclear thinking. Immediate medical care is required upon the first signs of these adverse effects.[8]
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 phase 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. However, more mild allergy symptoms, such as a rash, can occur at any time during treatment, even up to a week after treatment has ceased. For some people allergic to amoxicillin, the adverse effects can be fatal due to
anaphylaxis.[8]
Use of the amoxicillin/clavulanic acid combination for more than one week has caused a drug-induced immunoallergic-type
hepatitis in some patients. Young children having ingested acute overdoses of amoxicillin manifested
lethargy, vomiting, and
renal dysfunction.[39][40]
There is poor reporting of adverse effects of amoxicillin from clinical trials. For this reason, the severity and frequency of adverse effects from amoxicillin is probably higher than reported from clinical trials.[10]
Nonallergic rash
Between 3 and 10% of children taking amoxicillin (or
ampicillin) show a late-developing (>72 hours after beginning medication and having never taken penicillin-like medication previously) rash, which is sometimes referred to as the "amoxicillin rash". The rash can also occur in adults and may rarely be a component of the
DRESS syndrome.[41]
The rash is described as
maculopapular or morbilliform (
measles-like; therefore, in medical literature, it is called "amoxicillin-induced morbilliform rash".[42]). 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, this common amoxicillin rash and a dangerous allergic reaction cannot easily be distinguished by inexperienced persons, so a healthcare professional is often required to distinguish between the two.[43][44]
A nonallergic amoxicillin rash may also be an indicator of
infectious mononucleosis. Some studies indicate about 80–90% of patients with acute
Epstein–Barr virus infection treated with amoxicillin or ampicillin develop such a rash.[45]
Nonallergic amoxicillin rash eight days after first dose: This photo was taken 24 hours after the rash began.
Eight hours after the first photo, individual spots have grown and begun to merge.
At 23 hours after the first photo, the color appears to be fading, and much of rash has spread to confluence.
Amoxicillin (α-amino-p-hydroxybenzyl penicillin) is a semisynthetic derivative of penicillin with a structure similar to ampicillin but with better absorption when taken by mouth, thus yielding higher concentrations in blood and in urine.[51] Amoxicillin diffuses easily into tissues and body fluids. It will cross the
placenta and is excreted into
breastmilk in small quantities. It is metabolized by the liver and excreted into the urine. It has an onset of 30 minutes and a
half-life of 3.7 hours in newborns and 1.4 hours in adults.[18]
Amoxicillin was one of several
semisynthetic derivatives of 6-aminopenicillanic acid (
6-APA) developed by the
Beecham Group in the 1960s. It was invented by Anthony Alfred Walter Long and John Herbert Charles Nayler, two British scientists.[54][55] It became available in 1972 and was the second
aminopenicillin to reach the market (after
ampicillin in 1961).[56][57][58]Co-amoxiclav became available in 1981.[57]
Society and culture
Economics
Amoxicillin is relatively inexpensive.[59] In 2022, a survey of eight generic antibiotics commonly prescribed in the United States found their average cost to be about $42.67, while amoxicillin was sold for $12.14 on average.[60]
An
extended-release is available.[6][61] The intravenous form of amoxicillin is not sold in the United States.[62] When an intravenous aminopenicillin is required in the United States, ampicillin is typically used. When there is an adequate response to ampicillin, the course of antibiotic therapy may often be completed with oral amoxicillin.[63]
Amoxicillin is one of the semisynthetic penicillins discovered by former pharmaceutical company
Beecham Group. The patent for amoxicillin has expired, thus amoxicillin and co-amoxiclav preparations are marketed under various brand names across the world.[1]
Veterinary uses
Amoxicillin is also sometimes used as an
antibiotic for animals. The use of amoxicillin for animals intended for human consumption (
chickens,
cattle, and
swine for example) has been approved.[66]
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Further reading
Neal MJ (2002). Medical Pharmacology at a Glance (4th ed.). Oxford: Blackwell Science.
ISBN978-0-632-05244-8.