Friday, November 22, 2019

Amoxicillin: Uses, Indications, Dosages, Precautions, contraindications, Side Effects & Interactions


Pharmacotherapeutic: Penicillin
Clinical: Antibiotic
Amoxil, Apo-Amoxi (CAN), DisperMox,
Moxatag, Novamoxin (CAN), Nu-Amoxi
(CAN), Polymox, Trimox, Wymox
Pregnancy category B

General Information

Amoxicillin is a penicillin antibiotic. It is prescribed to treat a variety of infections, but is particularly useful for the treatment of ear, nose and throat infections, respiratory tract infections, cystitis, simple gonorrhea and some skin and soft tissue infections. Amoxicillin is sometimes associated with clavulanic acid (such as co-amoxiclav) to prevent bacteria from breaking down amoxicillin; this makes it effective against a wider range of bacteria than amoxicillin alone. The doses of co-amoxiclav are indicated in two numbers (for example, 500/125 is 500 mg of amoxicillin plus 125 mg of clavulanic acid)

Amoxicillin / co-amoxiclav can cause mild stomach discomfort and skin rashes. It can also cause a severe allergic reaction with fever, swelling of the mouth and tongue, itching and difficulty breathing


Interferes with cell wall replication of susceptible organisms by binding to the bacterial cell wall; the cell wall; bactericidal, lysis mediated by bacterial cell wall autolysis

Therapeutic Effect

Bactericidal in sensitive microorganisms, bactericidal effects for the following organisms: effective for gram-positive cocci (Staphylococcus aureus, Streptococcus pyogenes, Streptococcus faecalis, Streptococcus pneumoniae), gram-negative cocci (Neisseria gonorrhoeae, Neisseria meningitidis), gram-negative bacilli (Haemophilus influenzae, Proteus mirabilis, Escherichia coli, Salmonella), in combination with Helicobacter pylori, gram-positive bacilli (Corynebacterium diphtheriae, Listeria monocytogenes); gastric ulcer, negative b-lactam organisms

Availability (Rx)

Capsules: 250 mg, 500 mg
Powder for Oral Suspension: 125 mg/5 mL, 200 mg/5 mL,250 mg/5 mL or 400 mg/5 mL
Tablets: 250 mg, 500 mg, 875 mg
Tablets, Chewable: 125 mg, 200 mg,250 mg, 400 mg
Tablets, Extended-Release (Moxatag): 775 mg


Treatment of sensitive infections due to streptococci, E. coli, E. faecalis, P. mirabilis, H. influenzae, N. gonorrhoeae, including ears, nose and throat; lower respiratory tract; skin and skin texture; Urinary tract infections simple acute gonorrhea; H. pylori
Off-label: treatment of Lyme disease and typhoid fever. Post-exposure anthrax prophylaxis


Pregnancy B, breastfeeding, infants, hypersensitivity to cephalosporins, carbapenems; severe kidney disease, mononucleosis, phenylketonuria, diabetes, geriatrics, asthma, child, colitis, dialysis, eczema, pseudomembranous colitis, syphilis

Make sure to tell your doctor if:
• You are allergic to penicillin antibiotics or cephalosporin antibiotics
• You have glandular fever (infectious mononucleosis)
• You have a history of allergies
• have liver disorders or have had previous liver problems with amoxicillin / co-amoxiclav
• You are taking other medications

Indications and Dosages

Ear, nose, throat, genitourinary, skin, and skin-structure infections

Adults and children weighing 20 kg or more (44 lb)
• 250 mg every 8 hours; for serious infections, 500 mg every 8 hours or 875 mg every 12 h

Children aged 12 weeks or over weighing less than 20 kg
• 20 mg / kg per day in divided doses every 8 hours; for serious infections, 40 to 45 mg / kg / day in divided doses every 8 hours

Children under 12 weeks
• 30 mg / kg / day in separated doses every 12 hours

‣Tonsillitis or pharyngitis caused by Streptococcus pyogenes

E.R. tablets (MOXATAG)
Adults and children over 12 years
• 775 mg once a day for 10 days, taken within 1 hour of the end of the meal

‣Infections of the lower respiratory tract

Adults and children weighing 20 kg or more
• 875 mg every 12 h; for serious infections, 500 mg every 8 hours

Children aged 12 weeks or over weighing less than 20 kg
• 40 to 45 mg / kg per day in divided doses every 8 hours

Children under 12 weeks
• 30 mg / kg per day in separated doses every 12 hours

‣Gonorrhea and acute uncomplicated anogenital 

• 3 g once with 1 g probenecid. Continue therapy with tetracycline or erythromycin

Pre-pubescent boys aged 2 years or over
• 50 mg / kg plus probenecid 25 mg / kg in a single dose. Do not use in children under 2 years of age

‣Urethral infections

The dosage interval is changed based on creatinine clearance
• Creatinine clearance 10-30 ml / min. 250-500 mg every 12 hours
• Creatinine clearance <10 ml / min. 250-500 mg every 24 hours

‣Infection Helicobacter pylori infection to reduce the risk of recurrence of duodenal ulcer

• 1 g every 12 hours with 500 mg of clarithromycin every 12 hours and 30 mg of  lansoprazole every 12 hours for 14 days. Or 1 g every 8 hours with 30 mg of lansoprazole every 8 hours for 14 days

‣Bacterial endocarditis before dental, oral or upper respiratory tract procedures

Adults and children weighing 20 kg or more
• 2 g 1 h before the procedure

Children weighing less than 20 kg 
• 50 mg / kg 1 hour before 


Well absorbed from the gastrointestinal tract. Protein bond: 20%. Partially metabolized in the liver. Mainly excreted in the urine. Eliminated by hemodialysis. Half-life: 1–1.3 h (increase in renal failure)


PO path

• Identify allergies before use
• Give equal doses throughout the day regardless of food; If gastrointestinal disturbance occurs, give food; the product must be administered for 10-14 days to guarantee the death of the organism and prevent superinfection; store in an airtight container
• You can open the lids and drink the contents with liquids
• Suspension: shake well before each dose, it can be used alone or mixed in drinks, use immediately; the suspension can be kept in the refrigerator for 14 days
• Prolonged release: do not crush, chew or break; take with food


Hypersensitivity to amoxicillin


Individual drugs

Methotrexate: increased levels of methotrexate
Decreased: Hgb, WBC, platelets
Probenecid: increased amoxicillin levels, reduced renal excretion
Warfarin: increased anticoagulant effects

Drug classifications

• Anticoagulant drugs: amoxicillin and co-amoxiclav can alter the anticoagulant effect of these drugs
• Oral contraceptives: amoxicillin and co-amoxiclav can reduce the effectiveness of the oral contraceptive pill
• Alopurinol: amoxicillin can increase the probability of allergic skin reactions
• Oral typhoid fever vaccine: amoxicillin and co-amoxiclav inactivate this vaccine. Avoid taking these drugs for 3 days before and after receiving the vaccine

Drug / laboratory tests

It can increase ALT, AST, bilirubin, BUN, creatinine, serum LDH. It can cause a positive Coombs test

Drugs / food

None known


None significant

Side effects

• CNS: headache, convulsions, agitation, confusion, dizziness, insomnia
• GI: nausea, vomiting, diarrhea, abdominal pain, increased AST, ALT glossitis, colitis, pseudomembranous colitis, jaundice, cholestasis
• HEMA: anemia, hemolytic anemia, increased bleeding time, bone marrow depression, granulocytopenia
• INTEG: urticaria, rash
• SYSTEM: anaphylaxis, respiratory distress, serum sickness, Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis

Nursing considerations

Baseline assessment

• Ask for a history of allergies (especially penicillins, cephalosporins), kidney failure

Intervention / evaluation

• Mononucleosis patients should not receive amoxicillin because this class of medications can cause an erythematous rash
• Evaluate allergic reactions during treatment: skin rash, urticaria, itching, chills, fever, joints pain; angioedema can occur a few days after starting therapy; epinephrine and resuscitation

Equipment must be available for anaphylaxis

• Evaluate the intestinal model daily; diarrhea, cramps, blood in the stool; if you experience severe diarrhea,inform the attending physician; the product must be suspended; Pseudomembranous can to happen

• Use the drug with caution in patients with liver failure. Monitor liver and kidney function and CBC, as ordered, in patients on prolonged therapy. Also use with caution during breastfeeding and the elderly

• Identify urine production; if it decreases, inform your doctor (may indicate nephrotoxicity); Moreover, increase in BUN, creatinine, urinalysis, protein, blood

• Monitor blood tests: AST, ALT, CBC, Hct, bilirubin, LDH, alkaline phosphatase, Coombs' monthly test if the patient is on long-term therapy

• Monitor electrolytes: potassium, sodium, chloride monthly if the patient is on long-term therapy

• Do not confuse amoxicillin tablets with amoxicillin tablets for oral suspension (DisperMox). They are not interchangeable

• Wait for a treatment of at least 10 days for hemolytic streptococcal infections

• Monitor the patient for superinfection. If so, expect to stop the treatment and provide the treatment as ordered


Positive therapeutic result
• Absence of signs / symptoms of infection (WBC, 10,000 / mm3, WNL temp, absence of red draining wounds or pain in the ears)
• Prevention of endocarditis
• Resolution of ulcer symptoms

Patient / family teaching

• Instruct the patient to take all prescribed medications during the required time; do not double the dose; chewing form is available
• The space is evenly distributed
• Take with meals if gastrointestinal complaints occur
• Squeeze or chew the chewable tablets thoroughly before swallowing
• When prescribing a suspension of amoxicillin for a child, instruct parents to place it directly on the child's tongue for swallowing. If the problem persists, ask parents to mix the suspension dose with a cold formula or drink (milk, fruit juice, ginger beer, water) and have the child drink immediately
• Teach the patient to report adverse reactions and inform the doctor if the infection gets worse or does not improve after 72 hours
• Advise the patient to contact the doctor if they have vaginal itching, loose and smelly stools, diarrhea, sore throat, fever, fatigue, hairy tongue; may indicate superinfection or agranulocytopenia
• Advise the patient to inform the doctor about bloody diarrhea or pus, abdominal pain, which may indicates pseudomembranous colitis. Remind the patient that watery or bleeding stools can appear 2 or more months after antibiotic therapy and can be serious, requiring immediate treatment


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