Source: Medicines and Medical Devices Safety Authority (NZ) Revision Year: 2019 Publisher: Novartis New Zealand Limited, PO Box 99102, Newmarket, AUCKLAND 1149 Telephone: 0800 354 335
Amoxicillin is a penicillin and should not be given to patients with a history of hypersensitivity to beta-lactam antibiotics (e.g. penicillins, cephalosporins, carbapenem or monbactam). Potential cross allergy to other beta-lactams such as cephalosporins should be taken into account.
Known and suspected hypersensitivity to the active substance, to any of the penicillins or known hypersensitivity to any of the excipients.
Antibiotics have no place in trivial infections.
Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported in patients receiving beta-lactam antibiotics. Although anaphylaxis is more frequent following parenteral therapy, it has occurred in patients on oral therapy. Before initiating therapy with amoxicillin, careful enquiry should be made concerning previous hypersensitivity reactions to penicillins, cephalosporins. Cross-sensitivity between penicillins and cephalosporins is well documented. Patients should be told about the potential occurrence of allergic reactions and instructed to report them. If an allergic reaction occurs, amoxicillin should be discontinued and appropriate alternative therapy instituted. Patients should be told about the potential occurrence of allergic reactions and instructed to report them.
Serious anaphylactic reactions may require immediate emergency treatment with adrenaline or epinephrine. Oxygen, intravenous steroids and airway management, including intubation, may also be required.Amoxicillin should be given with caution to patients with lymphatic leukaemia, as they are susceptible to amoxicillin induced skin rashes.
Amoxicillin is not suitable for the treatment of some types of infection unless the pathogen is already documented and known to be susceptible or there is a very high likelihood that the pathogen would be suitable for treatment with amoxicillin. This particularly applies when considering the treatment of patients with urinary tract infections and severe infections of the ear, nose and throat.
Amoxicillin, an aminopenicillin, is not the treatment of choice in patients presenting with sore throat or pharyngitis because of the possibility that the underlying cause is infectious mononucleosis, in the presence of which there is a high incidence of rash if amoxicillin is used.Prolonged use may occasionally result in overgrowth of non-susceptible organisms.
Antibiotic associated pseudomembranous colitis has been reported with many antibiotics including amoxicillin. A toxin produced by Clostridium difficile appears to be the primary cause. The severity of the colitis may range from mild to life threatening. It is important to consider this diagnosis in patients who develop diarrhoea or colitis in association with antibiotic use (this may occur up to several weeks after cessation of antibiotic therapy). If prolonged or significant diarrhoea occurs or the patient experiences abdominal cramps, treatment should be discontinued immediately and the patient investigated further. Mild cases usually respond to drug discontinuation alone. However, in moderate to severe cases appropriate therapy with a suitable oral antibacterial agent effective against Clostridium difficile should be considered. Fluids, electrolytes and protein replacement should be provided when indicated. Drugs which delay peristalsis e.g. opiates and diphenoxylate with atropine (Lomotil) may prolong and/or worsen the conditions and should not be used.
Amoxicillin should not be used for the treatment of bacterial infections in patients with viral infections, presenting with sore throat, pharyngitis or infectious mononucleosis, as a high incidence of amoxicillin induced erythematous (morbilliform) rashes have been associated with glandular fever in patients receiving amoxicillin.
As with any potent drug, periodic assessment of renal, hepatic and haematopoietic function should be made during prolonged therapy. Elevated liver enzymes and changes in blood counts have been reported. Prolonged use may occasionally result in overgrowth of non-susceptible organisms. The possibility of superinfection with mycotic or bacterial pathogens should be particularly considered. If superinfection occurs (usually involving Aerobacter, Pseudomonas or Candida) discontinue amoxicillin and/or initiate appropriate therapy.
The Jarisch-Herxheimer reaction has been seen following amoxicillin treatment of Lyme disease. It results directly from the bactericidal activity of amoxicillin on the causative bacteria of Lyme disease, the spirochaete Borrelia burgdorferi. Patients should be reassured that this is a common and usually self-limiting consequence of antibiotic treatment of Lyme disease.
Pseudomembranous colitis should be borne in mind if severe persistent diarrhoea occurs (in most cases caused by Clostridium difficile) In this case Amoxicillin should be discontinued and an adequate therapy has to be started. The use of antiperistaltics is contraindicated.
Abnormal prolongation of prothrombin time has been reported rarely in patients receiving amoxicillin and oral anticoagulants. Appropriate monitoring should be undertaken when anticoagulation treatment is prescribed concurrently and the dose of the anticoagulant adjusted as necessary.
In patients with reduced urine output crystalluria has been observed very rarely, predominantly with parenteral therapy. During the administration of high doses of amoxicillin, it is advisable to maintain adequate fluid intake and urinary output in order to reduce the possibility of amoxicillin crystalluria (refer to Section 4.9 Overdose). The presence of high urinary concentrations of amoxicillin can cause precipitation of the product in urinary catheters. Therefore, catheters should be visually inspected at intervals. At high doses, adequate fluid intake and urinary output must be maintained to minimise the possibility of amoxicillin crystalluria.
Precaution should be taken in premature children and during neonatal period: renal, hepatic and haematological functions should be monitored.
As with other beta-lactams, the blood formula should be checked regularly during high-dose therapy.
High dose therapy with beta-lactams for patients with renal insufficiency or seizures history, treated epilepsy and meningeal affection, could exceptionally lead to seizures.
The occurrence of a generalized erythema with fever and pustules at the beginning of treatment should make suspect a generalized acute exanthematic pustulosis; this necessitates the interruption of therapy and contraindicated any further administration of amoxicillin.
Amoxicillin should be avoided if infectious momonucleosis is suspected since the occurrence of a morbillifrom rash has been associated with this condition following the use of amoxicillin.
Following single dose therapy of acute lower urinary tract infections, the urine should be cultured. A positive culture may be evidence of a complicated or upper urinary tract infection, and higher dose or prolonged course of treatment may be appropriate.
Patients suffering from severe gastrointestinal disturbances with diarrhoea and vomiting should not be treated with Ospamox, due to the risk of reduced absorption. In these cases, a parenteral treatment with amoxicillin is advisable.
Ospamox should be used with caution in patients with allergic diathesis and asthma.
Ospamox Suspensions, which contain aspartame, should be used with caution in patients with phenylketonuria.
Ospamox Paediatric Drops contain sucrose and saccharin sodium as sweeteners.
Ospamox Powder for Oral Suspension and Ospamox Paediatric Drops contain sodium benzoate.
Dosage should be adjusted in patients with renal impairment (refer to Section 4.2 Dose and method of administration).
No data available.
Precaution should be taken in premature children and during neonatal period: renal, hepatic and haematological functions should be monitored.
At high risk concentrations, amoxicillin may diminish the results of serum glycaemia levels. It is recommended that when testing for the presence of glucose in urine during amoxicillin treatment, enzymatic glucose oxidase methods should be used. Due to the high urinary concentrations of amoxicillin, false positive readings are common with chemical methods.
Following administration of ampicillin to pregnant women, a transient decrease in plasma concentration of total conjugated estriol, estriol-glucuronide, conjugated estrone and estradiol has been noted. This effect may also occur with amoxicillin.
Amoxicillin may interfere with protein testing when colorimetric methods are used.
Concurrent administration of allopurinol during treatment with amoxicillin can increase the likelihood of allergic skin reactions.
Concomitant administration of amoxicillin and anticoagulants, such as coumarin, may increase the incidence of bleeding due to prolongation of prothrombin time. Appropriate monitoring should be undertaken when anticoagulation treatment is prescribed concurrently and the dose of the anticoagulant adjusted as necessary. A large number of cases showing an increase of oral anticoagulant activity has been reported in patients receiving antibiotics. The infectious and inflammatory context, age and the general status of the patient appear as risk factors. In these circumstances, it is difficult to know the part of the responsibility between the infectious disease and its treatment in the occurrence of INR disorders. However, some classes of antibiotics are more involved, notably fluoroquinolones, macrolides, cyclines, cotrimoxazole and some cephalosporins
There is a possibility that the bactericidal action of amoxicillin could be antagonised on coadministration with bacteriostatic agents such as macrolides, tetracyclines, sulphonamides or chloramphenicol.
An increase in the absorption of digoxin is possible on concurrent administration with amoxicillin. A dose adjustment of digoxin may be necessary.
Interaction between amoxicillin and methotrexate leading to methotrexate toxicity has been reported. Serum methotrexate levels should be closely monitored in patients who receive amoxicillin and methotrexate simultaneously. Amoxicillin decreases the renal clearance of methotrexate, probably by competition at the common tubular secretion system.
Concomitant use of probenecid is not recommended. Probenecid decreases the renal tubular secretion of amoxicillin. Concurrent use with amoxicillin may result in increased and prolonged levels of amoxicillin in serum and bile.
Administration of amoxicillin can transiently decrease the plasma level of estrogens and progesterone, and may reduce the efficacy of oral contraceptives. It is therefore recommended to take supplemental non-hormonal contraceptive measures.
Forced diuresis leads to a reduction in blood concentrations by increased elimination of amoxicillin.
It is recommended that when testing for the presence of glucose in urine during amoxicillin treatment, enzymatic glucose oxidase methods should be used. Due to the high urinary concentrations of amoxicillin, false positive readings are common with chemical methods
The occurrence of diarrhoea may impair the absorption of other medicines consequently limiting their efficacy.
Amoxicillin may decrease the amount of urinary estriol in pregnant women.
At high concentrations, amoxicillin may diminish the results of serum glycemia levels.
Amoxicillin may interfere with protein testing when colormetric methods are used.
Reproduction studies have been performed in mice and rats at doses up to ten times the human dose and these studies have revealed no evidence of impaired fertility or harm to the foetus due to amoxicillin.
Category A.
Assigned Category A by the Australian Drug Evaluation Committee. This category includes medicines, which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the foetus having been observed. The safety of amoxicillin for use in human pregnancy has not been established by well controlled studies in pregnant women. Amoxicillin may be used in pregnancy when the potential benefits outweigh the potential risks associated with treatment.
Oral ampicillin class antibiotics are generally poorly absorbed during labour. Studies in guinea pigs have shown that intravenous administration of ampicillin decreased the uterine tone, frequency and duration of contractions. However, it is not known whether the use of amoxicillin in humans during labour or delivery has immediate or delayed adverse effects on the foetus, prolongs the duration of labour or increases the likelihood that forceps delivery or other obstetrical intervention or resuscitation of the newborn will be necessary.
Residual amoxicillin may be present in breast milk at levels corresponding to approximately 0.7% of the maternal dose. Penicillins are considered to be compatible with breastfeeding although there are theoretical risks of alterations to infant bowel flora and allergic sensitisation. So far, no detrimental effects for the breast-fed infant have been reported after taking amoxicillin. Amoxicillin can be used during breast-feeding. However, breast-feeding must be stopped if gastrointestinal disorders (diarrhoea, candidosis or skin rash) occur in the newborn.
This medicine is presumed to be safe or unlikely to produce an effect. However, undesirable effects may occur (e.g. allergic reactions, dizziness, convulsions), which may influence the ability to drive and use machines (see Section 4.8 Adverse effects (Undesirable effects)).
Side-effects, as with other penicillins, are uncommon and mainly of a mild and transitory nature. The majority of the side-effects listed below are not unique to amoxicillin and may occur when using other penicillins.
Undesirable effects are classified systematically and by frequency according to the following convention: very common (above 1 in 10); common (from 1 in 100 to 1 in 10); uncommon (from 1 in 1000 to 1 in 100; rare (from 1 in 10,000 to 1 in 1,000); very rare (below 1 in 10,000). Unless otherwise stated, the frequency of adverse events has been derived from more than 30 years of post-marketing reports.
Very rare: Reactions such as anaemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia and leucopenia (including severe neutropenia or agranulocytosis), have been reported during therapy with other penicillins. All were reversible on discontinuation of therapy and are believed to be hypersensitivity phenomena. Prolongation of bleeding time and prothrombin time have also been reported rarely (refer to Section 4.4 Special warnings and precautions for use).
Very rare: As with other antibiotics, severe allergic reactions, including angioneurotic oedema, anaphylaxis (refer to Section 4.4 Special warnings and precautions for use), serum sickness and allergic vasculitis. If a hypersensitivity reaction is reported, the treatment must be discontinued. (See also Skin and subcutaneous tissue disorders).
Uncommon: Prolonged and repeated use of the preparation can result in superinfections and colonisation with resistant organisms or yeasts such as oral and vaginal candidiasis.
Common: Gastric complaints, nausea, loss of appetite, flatulence, soft stools, diarrhoea, enanthemas (particularly in the region of the mouth), dry mouth, taste disturbances. These effects on the gastrointestinal system are mostly mild and frequently disappear either during the treatment or very soon after completion of therapy. The occurrence of these side effects can generally be reduced by taking amoxicillin during meals.
Uncommon: Vomiting.
Rare: Superficial discoloration of the teeth (especially with the suspension). Usually the discoloration can be removed by teeth brushing.
Very rare: Mucocutaneous candidiasis. Antibiotic associated colitis including pseudomembranous colitis and haemorrhagic colitis. If severe and persistent diarrhoea occurs, the very rare possibility of pseudomembranous colitis should be considered. The administration of anti-peristaltic agents is contraindicated.
Development of a black hairy tongue.
Rare: Drug fever
Rare: Hepatitis and cholestatic jaundice.
Uncommon: Moderate and transient increase of liver enzymes. The significance of a rise in liver enzymes is unclear
Rare: Hyperkinesia, dizziness and convulsions. Convulsions may occur in patients with impaired renal function, epilepsy meningitis, or in those receiving high doses.
Common: Cutaneous reactions such as exanthema, pruritus, urticaria, erythematous maculopapular rash; the typical morbilliform exanthema occurs 5 to 11 days after commencement of therapy. The immediate appearance of urticaria indicates an allergic reaction to amoxicillin and therapy should therefore be discontinued. Note urticaria, other skin rashes and serum sickness-like reactions may be controlled with anihistamines and, if necessary, systemic corticosteroids.
Rare: Skin reactions such as Angioneurotic oedema (Quincke’s oedema, erythema multiforme exudativum, exsudativum, acute generalized pustulosis, Lyell’s syndrome, Stevens-Johnson syndrome, toxic epidermal necrolysis, bullous and exfoliative dermatitis and acute generalised exanthematous pustulosis, Jarisch-Herxheimer reaction (see also Immune system disorders).
Rare: Interstitial nephritis, crystalluria (refer to Section 4.9 Overdose)
The incidence of these adverse events was derived from clinical studies involving a total of approximately 6,000 adult and paediatric patients taking amoxicillin.
Reporting suspected adverse reactions after authorisation of the medicine is important. It allows continued monitoring of the benefit/risk balance of the medicine. Healthcare professionals are asked to report any suspected adverse reactions https://nzphvc.otago.ac.nz/reporting/.
None known.
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