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amoxicillin, amoxicillin trihydrate
Pharmacologic class: Aminopenicillin
Therapeutic class: Anti-infective
Pregnancy risk category B
Inhibits cell-wall synthesis during bacterial multiplication, leading to cell death. Shows enhanced activity toward gram-negative bacteria compared to natural and penicillinase-resistant penicillins.
Capsules: 250 mg, 500 mg
Powder for oral suspension: 50 mg/ml and 125 mg/5 ml (pediatric), 200 mg/5 ml, 250 mg/5 ml, 400 mg/5 ml
Tablets: 500 mg, 875 mg
Tablets for oral suspension: 200 mg, 400 mg
Tablets (chewable): 125 mg, 200 mg, 250 mg, 400 mg
Indications and dosages
➣ Uncomplicated gonorrhea
Adults and children weighing at least 40 kg (88 lb): 3 g P.O. as a single dose
Children ages 2 and older weighing less than 40 kg (88 lb): 50 mg/kg P.O. given with probenecid 25 mg/kg P.O. as a single dose
➣ Bacterial endocarditis prophylaxis for dental, GI, and GU procedures
Adults: 2 g P.O. 1 hour before procedure
Children: 50 mg/kg P.O. 1 hour before procedure
➣ Lower respiratory tract infections caused by streptococci, pneumococci, non-penicillinase-producing staphylococci, and Haemophilus influenzae
Adults and children weighing more than 20 kg (44 lb): 875 mg P.O. q 12 hours or 500 mg P.O. q 8 hours
Children weighing less than 20 kg (44 lb): 45 mg/kg/day P.O. in divided doses q 12 hours or 40 mg/kg/day P.O. in divided doses q 8 hours
➣ Ear, nose, and throat infections caused by streptococci, pneumococci, non-penicillinase-producing staphylococci, and H. influenzae; GU infections caused by Escherichia coli, Proteus mirabilis, and Streptococcus faecalis
Adults and children weighing more than 20 kg (44 lb): 500 mg P.O. q 12 hours or 250 mg P.O. q 8 hours
Children weighing less than 20 kg (44 lb): 45 mg/kg/day P.O. in divided doses q 12 hours or 20 to 40 mg/kg P.O. in divided doses q 8 hours
➣ Eradication of Helicobacter pylori to reduce risk of duodenal ulcer recurrence
Adults: 1 g P.O. q 12 hours for 14 days in combination with clarithromycin and lansoprazole, or in combination with lansoprazole alone as 1 g t.i.d. for 14 days
➣ Postexposure anthrax prophylaxis
Adults: 500 mg P.O. t.i.d. for 60 days
Children: 80 mg/kg/day P.O. t.i.d. for 60 days
➣ Skin and skin-structure infections caused by streptococci (alpha- and beta-hemolytic strains), staphylococci, and E. coli
Adults: 500 mg P.O. q 12 hours to 250 mg P.O. q 8 hours. For severe infections, 875 mg P.O. q 12 hours or 500 mg P.O. q 8 hours.
Children older than age 3 months: 25 mg/kg/day P.O. in divided doses q 12 hours or 20 mg/kg/day P.O. in divided doses every 8 hours. For severe infections, 45 mg/kg/day P.O. in divided doses q 12 hours or 40 mg/kg/day P.O. in divided doses every 8 hours.
• Renal impairment
• Infants ages 3 months and younger
• Chlamydia trachomatis infection in pregnant patients
• Hypersensitivity to drug or any penicillin
Use cautiously in:
• severe renal insufficiency, infectious mononucleosis, hepatic dysfunction
• pregnant patients.
☞ Ask about history of penicillin allergy before giving.
• Give with or without food.
• Store liquid form in refrigerator when possible.
• Know that maximum dosage for infants ages 3 months and younger is 30 mg/kg/day divided q 12 hours.
CNS: lethargy, hallucinations, anxiety, confusion, agitation, depression, dizziness, fatigue, hyperactivity, insomnia, behavioral changes, seizures (with high doses)
GI: nausea, vomiting, diarrhea, bloody diarrhea, abdominal pain, gastritis, stomatitis, glossitis, black "hairy" tongue, furry tongue, enterocolitis, pseudomembranous colitis
GU: vaginitis, nephropathy, interstitial nephritis
Hematologic: eosinophilia, anemia, thrombocytopenia, thrombocytopenic purpura, leukopenia, hemolytic anemia, agranulocytosis, bone marrow depression
Hepatic: cholestatic jaundice, hepatic cholestasis, cholestatic hepatitis, nonspecific hepatitis
Other: superinfections (oral and rectal candidiasis), fever, anaphylaxis
Drug-drug. Allopurinol: increased risk of rash
Chloramphenicol, macrolides, sulfonamides, tetracycline: decreased amoxicillin efficacy
Hormonal contraceptives: decreased contraceptive efficacy
Probenecid: decreased renal excretion
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, eosinophils, lactate dehydrogenase: increased levels
Granulocytes, hemoglobin, platelets, white blood cells: decreased values Direct Coombs' test, urine glucose, urine protein: false-positive results
Drug-food. Any food: delayed or reduced drug absorption
Drug-herbs. Khat: decreased antimicrobial efficacy
• Monitor for signs and symptoms of hypersensitivity reaction.
☞ Evaluate for seizures when giving high doses.
• Monitor patient's temperature and watch for other signs and symptoms of superinfection (especially oral or rectal candidiasis).
☞ Instruct patient to immediately report signs and symptoms of hypersensitivity reactions, such as rash, fever, or chills.
• Tell patient he may take drug with or without food.
• Tell patient not to chew or swallow tablets for suspension, because they're not meant to be dissolved in mouth.
• Advise patient to minimize GI upset by eating small, frequent servings of food and drinking plenty of fluids.
• Tell patient taking hormonal contraceptives that drug may reduce contraceptive efficacy. Suggest she use alternative birth control method.
• Inform patient that drug lowers resistance to other types of infections. Instruct him to report new signs and symptoms of infection, especially in mouth or rectum.
• Tell parents they may give liquid form of drug directly to child or may mix it with foods or beverages.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, and herbs mentioned above.
ClassificationTherapeutic: anti infectives
- Skin and skin structure infections,
- Otitis media,
- Respiratory infections,
- Genitourinary infections.
- Haemophilus influenzae,
- Escherichia coli,
- Proteus mirabilis,
- Neisseria meningitidis,
- N. gonorrhoeae,
- Chlamydia trachomatis,
- Borrelia burgdorferi,
- H. pylori.
Time/action profile (blood levels)
|PO||30 min||1–2 hr||8–12 hr|
Adverse Reactions/Side Effects
Central nervous system
- seizures (high doses) (life-threatening)
- pseudomembranous colitis (life-threatening)
- diarrhea (most frequent)
- ↑ liver enzymes
- rash (most frequent)
- blood dyscrasias
- allergic reactions including anaphylaxis (life-threatening)
- serum sickness (life-threatening)
Drug-Drug interactionProbenecid ↓ renal excretion and ↑ blood levels of amoxicillin—therapy may be combined for this purpose.May ↑ effect of warfarin.May ↓ effectiveness of oral contraceptives.Allopurinol may ↑ frequency of rash.
Renal ImpairmentOral (Adults CCr 10–30 mL/min) 250–500 mg q 12 hr.
Renal ImpairmentOral (Adults CCr <10 mL/min) 250–500 mg q 24 hr.
Availability (generic available)
- Assess for infection (vital signs; appearance of wound, sputum, urine, and stool; WBC) at beginning of and throughout therapy.
- Obtain a history before initiating therapy to determine previous use of and reactions to penicillins or cephalosporins. Persons with a negative history of penicillin sensitivity may still have an allergic response.
- Observe for signs and symptoms of anaphylaxis (rash, pruritus, laryngeal edema, wheezing). Notify health care professional immediately if these occur.
- Obtain specimens for culture and sensitivity prior to therapy. First dose may be given before receiving results.
- Monitor bowel function. Diarrhea, abdominal cramping, fever, and bloody stools should be reported to health care professional promptly as a sign of pseudomembranous colitis. May begin up to several weeks following cessation of therapy.
- Lab Test Considerations: May cause ↑ serum alkaline phosphatase, LDH, AST, and ALT concentrations.
- May cause false-positive direct Coombs’ test result.
Potential Nursing DiagnosesRisk for infection (Indications, Side Effects)
Noncompliance (Patient/Family Teaching)
- Oral: Administer around the clock. May be given without regard to meals or with meals to decrease GI side effects. Capsule contents may be emptied and swallowed with liquids. Extended-release tablets should be swallowed whole; do not crush, break, or chew. Chewable tablets should be crushed or chewed before swallowing with liquids.
- Shake oral suspension before administering. Suspension may be given straight or mixed in formula, milk, fruit juice, water, or ginger ale. Administer immediately after mixing. Discard refrigerated reconstituted suspension after 10 days.
- Instruct patients to take medication around the clock and to finish the drug completely as directed, even if feeling better. Advise patients that sharing of this medication may be dangerous.
- Pediatric: Teach parents or caregivers to calculate and measure doses accurately. Reinforce importance of using measuring device supplied by pharmacy or with product, not household items.
- Advise patient to report the signs of superinfection (furry overgrowth on the tongue, vaginal itching or discharge, loose or foul-smelling stools) and allergy.
- Instruct patient to notify health care professional immediately if diarrhea, abdominal cramping, fever, or bloody stools occur and not to treat with antidiarrheals without consulting health care professional.
- Instruct the patient to notify health care professional if symptoms do not improve.
- Teach patients with a history of rheumatic heart disease or valve replacement the importance of using antimicrobial prophylaxis before invasive medical or dental procedures.
- Instruct female patients taking oral contraceptives to use an alternate or additional nonhormonal method of contraception during therapy with amoxicillin and until next menstrual period.
- Resolution of the signs and symptoms of infection. Length of time for complete resolution depends on the organism and site of infection.
- Endocarditis prophylaxis.
- Eradication of H. pylori with resolution of ulcer symptoms.
- Prevention of inhalational anthrax (postexposure).