Generality
Amoxicillin is an antibiotic drug, a semi-synthetic penicillin patented by the pharmaceutical company SmithKline Beecham, both as a simple amoxicillin and as tablets containing amoxicillin and clavulanic acid.
Other names used for amoxicillin-based drugs are Velamox ®, Sintopen ®, Sievert ®, Pamocil ®, Mopen ®, Amox ® and Amoflux ®, while for the amoxicillin / clavulanic acid the most used names are Abba ®, Aklav ®, Anival ®, Aveggio ®, Clavulin ®, Neoduplamox ® and Puriclav ®.
Action mechanism
Amoxicillin fights bacteria by inhibiting the synthesis of their cell wall, more specifically the drug inhibits cross-linking between linear polymers of peptidoglycan (the major component of the cell wall of both Gram positive and Gram negative bacteria).
Amoxicillin is an antibiotic similar to penicillin, from which it differs only in the additional presence of a hydroxyl group on the benzene ring and of an amino group on the side chain; the presence of the amino group (NH 2 ) on the side chain of amoxicillin hinders the ability of beta-lactamate enzymes to open the beta-lactam ring of the antibiotic, thus making it inactive.
What diseases are used for?
Amoxicillin is a bactericidal antibiotic with a satisfactory range of action, used in the treatment of most bacterial infections; in many cases amoxicillin is the first choice drug compared to other beta-lactam antibiotics, because it is much better absorbed after oral administration. Amoxicillin is also one of the most widely used antibiotics in children.
To increase its efficiency, amoxicillin is often administered in association with clavulanic acid, in a single pharmaceutical preparation; the latter active ingredient is in fact an inhibitor of beta-lactamase enzymes that inactivate beta-lactam antibiotics, as such contributes to increasing antibiotic efficiency.
Amoxicillin is used in the treatment of many diseases, such as in triple therapy for the eradication of Helicobacter pylori, in cases of pharyngitis and streptococical laryngitis, in urinary tract infections (cystitis, urethritis, pyelonephritis, gonorrhea), in pneumonia, in skin and soft tissue infections, in the treatment of salmonellosis.
The use of amoxicillin is also recommended in the prophylaxis and treatment of anthrax, to prevent the appearance of bacterial endocarditis in people with a high risk factor (for example patients who undergo dental procedures), and also to prevent the appearance of Streptococcus pneumoniae infections in people without a spleen.
Posology and Mode of Use
The recommended dose of amoxicillin used in triple therapy for the eradication of Helicobacter pylori is 2000 mg / day, to be divided into two daily administrations.
In the treatment against actinomycosis, the recommended dose of amoxicillin is 1500 mg / day, taken in three daily administrations, or 1750 mg / day to be divided into two daily administrations of 875 mg each. The recommended duration of treatment is 6 months.
For anthrax prophylaxis, the recommended dose of amoxicillin is 500 mg every 8 hours. Even if oral amoxicillin is not considered a first choice treatment, it can still be used to complete a 60-day cycle after taking ciprofloxacin for 10-14 days, in pregnant women or during lactation or in patients with contraindications to ciprofloxacin. It should be noted that the total duration of the antibacterial treatment is 60 days. In children the recommended dose of amoxicillin to be used in prophylaxis against anthrax is 80 mg / kg / day, divided into 4 equal doses given every 8 hours. However, regardless of the weight of the child, it is recommended not to exceed the daily threshold of 1500-2000 mg / day. Although amoxicillin is not indicated as a first-line treatment for anthrax, in children it is recommended to end the 60-day treatment cycle after 10 days of treatment with ciprofloxacin or doxycycline.
To prevent the appearance of bacterial endocarditis the recommended dose of amoxicillin is 2000 mg, administered orally one hour before the dental medical procedure. Amoxicillin is considered to be the first choice antibiotic to be used in the prophylaxis of bacterial endocarditis in patients who undergo certain medical procedures such as oral, respiratory tract or esophageal tract; however, amoxicillin is not recommended in patients at high risk of bacterial endocarditis, such as those with prosthetic valves implanted in the heart or who have already been affected by bacterial endocarditis; for these categories of patients the use of parenteral antimicrobial therapy is recommended.
In the treatment of Chlamydia infection the recommended dose of amoxicillin is 1500 mg / day, divided into 3 daily administrations for a duration of 7 days. This type of treatment is particularly indicated in pregnant women as an alternative to erythromycin in case of sensitivity to macrolide antibiotics; however, it must be emphasized that amoxicillin is not active against Chlamydia trachomatis .
In the treatment of bacterial cystitis, the recommended dose of amoxicillin is 750-1500 mg / day, taken orally and divided into three daily administrations for a period that can vary from three to seven days. The same doses and treatment modalities can be used in case of urinary tract infections.
For the treatment of Lyme disease the recommended dose is 1500 mg of amoxicillin per day, divided into three daily administrations, for a period that can vary from two weeks to a month. Many patients with Lyme disease experience the so-called Jarisch-Herxheimer reaction during the first 24 hours of treatment with amoxicillin, which includes fever, increased pain and hot flushes; this manifestation, however, does not necessarily indicate an allergy to amoxicillin. The same reactions can be attenuated by administering aspirin and prednisone before taking the antibiotic. Sometimes doctors also prefer to add probenicid, but the usefulness of this addition has not yet been confirmed. Other doctors instead prefer to use - simultaneously with the treatment of Lyme disease - other antibiotics, such as cefuroxime, doxylicin and azithromycin.
In the treatment of otitis media, pneumonia, skin and soft tissue infections, sinusitis, bronchitis and upper respiratory tract infections, the recommended dose of amoxicillin is 750-1500 mg / day, divided into three daily administrations for a period ranging from 10 to 14 days and depends on the individual response to antibiotic therapy. For the treatment of the aforementioned diseases, in children from 4 weeks to 3 months of age the recommended dose of amoxicillin drops to 20-30 mg / kg / day, divided into two daily administrations, one every 12 hours, while for children from 4 months to 12 years the recommended dose is 20-50 mg / kg / day, always divided into two daily administrations, one every 12 hours.
For the treatment of tonsillitis, the recommended dose of amoxicillin is 750-1500 mg / day, divided into three daily administrations for a period of 7 - 10 days depending on the severity of the infection and the individual therapeutic response; in case of secondary infections caused by Streptococcus pyogens prolonged release tablets can be used and a single daily administration of 775 mg is sufficient, after meals, for 10 days.
Contraindications and Warnings
Following oral administration, amoxicillin is quickly absorbed in the gastrointestinal tract; naturally, the presence of food slows down the rate at which the antibiotic is absorbed but does not affect the percentage absorbed; Amoxicillin has an oral bioavailability variable from 70 to 90%. The absorption of amoxicillin in the intestinal lumen takes place via the carriers that carry the dipeptides.
Administration of amoxicillin can cause allergic and hypersensitivity reactions, therefore in similar situations it is recommended to stop the therapy and resort to an alternative treatment. Particular care should be taken in treating patients who have experienced hypersensitivity episodes against imipenem and cephalosporins, or who suffer from asthma and eczema of allergic origin.
When amoxicillin is used in Chlamydia therapy in pregnant women, further monitoring is recommended three weeks after the end of treatment and other checks from the 36th to the 40th week of pregnancy to ascertain complete recovery.
If amoxicillin is administered to patients suffering from colitis, an exacerbation of the side effects induced by the drug may occur; in other cases, severe persistent diarrhea may occur, in similar situations it is advisable to carry out tests to verify whether it is pseudomembranous colitis induced by the antibiotic. If the tests are positive then it is advisable to suspend amoxicillin therapy and resort to an alternative antibiotic treatment, administering to the patient fluids, electrolytes and antibacterial drugs effective against C.difficile (causative agent responsible for pseudomembranous colitis).
If you have been treated with amoxicillin and need to measure glucose in your urine, you need to tell the analysis laboratory; in fact, the drug can give a false positive result in the measurement of glucose in urine performed with Fehling's or Benedict's reagent.
Particular attention should also be paid when administering amoxicillin together with oral contraceptives, given that amoxicillin can reduce the contraceptive efficacy of the pills, reducing their absorption. Therefore it is recommended to adopt additional contraceptive measures during the entire duration of the therapeutic cycle with amoxicillin and also up to a week later.
Pregnancy and breastfeeding
Although there are no specific studies regarding the use of amoxicillin during pregnancy and lactation, those conducted so far on animals - with doses around 10 times greater than those used in humans - have not shown any risk or adverse effect on the fetus. In a study conducted in the United States of America, which involved around 230, 000 pregnant women from 1985 to 1992, about 8, 000 of the women studied were exposed to amoxicillin during the first trimester of pregnancy (the most at risk of fetal malformations and abortions) ); at the end of this study it was noted that - in the group treated with amoxicillin - the percentage of fetal malformations and abortions was similar or lower than the observed average.
Amoxicillin is excreted in breast milk, but its use during lactation is considered acceptable; in several clinical cases, when the mother was given 1 gram of amoxicillin the levels of the drug in the milk were low, such that they could not cause side effects in the child. However, in certain cases, amoxicillin can cause a disturbance of the intestinal flora of the newborn, with the appearance of diarrhea; these episodes have been reported sporadically.
Side and Undesirable effects
The undesirable effects deriving from the therapeutic use of amoxicillin affect about 30% of patients and in almost all cases tend to resolve spontaneously. It is important to keep in mind that amoxicillin is one of the most sold and used drugs in the world, so despite the high number of reports, it must always be taken into account that the drug is used almost by all categories of patients.
The most frequently observed undesirable effect - administering amoxicillin or other penicillins - and that of hypersensitivity to the drug, which manifests itself with skin rash, erythema, anaphylaxis, anemia and thrombocytopenia. Fortunately, these side effects disappear on their own after treatment is stopped; in hypersensitive individuals (whose number is considerable) alternative therapies are used with macrolide antibiotics, which are much better tolerated from this point of view. Other side effects that may occur during the use of amoxicillin, even if rare, concern the gastrointestinal tract such as diarrhea, nausea, stomatitis and vomiting, mostly resulting from oral administration. Even rarer side effects are related to the blood and liver systems: thrombocytopenia, alteration of platelet function, increase in liver transaminases, jaundice and reversible agranulocytosis.
