Moxatag (amoxicillin) Side Effects, Warnings, and Interactions

Moxatag (amoxicillin) is a penicillin antibiotic used to treat bacterial infections of the middle ear, tonsils, throat, larynx (laryngitis), bronchi (bronchitis), lungs (pneumonia), urinary tract, and skin. Moxatag is also used to treat gonorrhea.

Common side effects of amoxicillin include diarrhea, dizziness, heartburn, insomnia, nausea, vomiting, itching, confusion, abdominal pain, easy bruising, bleeding, rash, and allergic reactions.

Serious but rare side effects of amoxicillin include seizures, severe allergic reactions (anaphylaxis), and low platelet (thrombocytopenia) or red blood cell count.

Amoxicillin can alter the normal bacteria in the colon and encourage overgrowth of some bacteria such as Clostridium difficile which causes inflammation of the colon (pseudomembranous colitis).

Amoxicillin is rarely associated with important drug interactions.

Penicillins such as amoxicillin are generally considered safe for use by pregnant women who are not allergic to penicillin. Small amounts of amoxicillin may be excreted in breast milk and may cause diarrhea or allergic responses in nursing infants. Amoxicillin is generally considered safe to use while breastfeeding.

Side effects due to amoxicillin include

• diarrhea,
• dizziness,
• heartburn,
• insomnia,
• nausea,
• itching,
• vomiting,
• confusion,
• abdominal pain,
• easy bruising,
• bleeding,
• rash, and
• allergic reactions.

People who are allergic to the cephalosporin class of antibiotics, which are related to the penicillins, for example, cefaclor (Ceclor), cephalexin (Keflex), and cefprozil (Cefzil), may or may not be allergic to penicillins.

Serious but rare reactions include:

• seizures,
• severe allergic reactions (anaphylaxis), and
• low platelet (thrombocytopenia) or red blood cell count.

Amoxicillin can alter the normal bacteria in the colon and encourage overgrowth of some bacteria such as Clostridium difficile which causes inflammation of the colon (pseudomembranous colitis). Patients who develop signs of pseudomembranous colitis after starting amoxicillin (diarrhea, fever, abdominal pain, and possibly shock) should contact their physician immediately.

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Clinical Study Experience

Tonsillitis and/or Pharyngitis

In a controlled Phase 3 trial, 302 adult and pediatric patients ( ≥ 12 years) were treated with Moxatag 775 mg once-daily for 10 days and 306 adult and pediatric patients ( ≥ 12 years) were treated with penicillin VK 250 mg QID for 10 days.

In this clinical trial, the majority of treatment-emergent adverse reactions were of a mild and transient nature with similar frequency reported in both treatment groups. Discontinuation due to drug-related treatment-emergent adverse reactions occurred in 1.3% of the Moxatag-treated patients and 3.3% of the penicillin VK-treated patients.

The most frequently reported adverse reactions ( ≥ 1%) which were suspected or probably drug-related are shown in Table 1.

Table 1: Drug-Related Treatment-Emergent Adverse Reactions by System Organ Class Experienced by ≥ 1% of Patients in Either Treatment Group – ITT/Safety Population

Adverse Reactions For Other Amoxicillin Products

The following adverse reactions have been reported for other products containing amoxicillin:

Infections and Infestations: Mucocutaneous candidiasis.

Gastrointestinal: Nausea, vomiting, diarrhea, and hemorrhagic/pseudomembranous colitis.

Onset of pseudomembranous colitis symptoms may occur during or after antibiotic treatment.

Hypersensitivity Reactions: Anaphylaxis.

Serum sickness like reactions, erythematous maculopapular rashes, erythema multiforme, Stevens-Johnson Syndrome, exfoliative dermatitis, toxic epidermal necrolysis, acute generalized exanthematous pustulosis, hypersensitivity vasculitis and urticaria have been reported. (NOTE: These hypersensitivity reactions may be controlled with antihistamines and, if necessary, systemic corticosteroids. Whenever such reactions occur, amoxicillin should be discontinued unless, in the opinion of the physician, the condition being treated is life-threatening and amenable only to amoxicillin therapy.)

Liver: A moderate rise in AST (SGOT) and/or ALT (SGPT) has been noted, but the significance of this finding is unknown. Hepatic dysfunction including cholestatic jaundice, hepatic cholestasis and acute cytolytic hepatitis have been reported.

Hemic and Lymphatic Systems: Anemia, including hemolytic anemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia, leukopenia, and agranulocytosis have been reported during therapy with penicillins. These reactions are usually reversible on discontinuation of therapy and are believed to be hypersensitivity phenomena.

Central Nervous System: Reversible hyperactivity, agitation, anxiety, insomnia, confusion, convulsions, behavioral changes, and/or dizziness have been reported rarely.

Renal: Crystalluria has also been reported.

Miscellaneous: Tooth discoloration (brown, yellow, or gray staining) has been rarely reported. Most reports occurred in pediatric patients. Discoloration was reduced or eliminated with brushing or dental cleaning in most cases.

Probenecid

Probenecid decreases the renal tubular secretion of amoxicillin. Concurrent use of Moxatag and probenecid may result in increased and prolonged blood levels of amoxicillin. The clinical relevance of this finding has not been evaluated.

Other Antibiotics

Chloramphenicol, macrolides, sulfonamides, and tetracyclines may interfere with the bactericidal effects of penicillin. This has been demonstrated in vitro; however, the clinical significance of this interaction is not well documented.

Oral Contraceptives

As with other antibiotics, amoxicillin may affect the gut flora, leading to lower estrogen reabsorption and potentially resulting in reduced efficacy of combined oral estrogen/progesterone contraceptives.