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Co-amoxiclav is one of the potent broad spectrum antibiotics in the market today. It is made up of amoxicillin with beta-lactamase inhibitor clavulanic acid. It targets both gram positive and gram negative organisms especially those who have developed resistance to beta-lactam antibiotics.


Chemical nature

Co-amoxiclav's major component is amoxicillin, which is the 4-hydroxy analog of ampicillin. It acts on the bacterial cell walls by making them more porous. Despite its wide range of germicidal action, organisms that produces the enzyme beta-lactamase. Beta-lactamase protects the bacteria from being attacked by amoxicillin. Clavulanic acid, a mild antibacterial agent, helps amoxicillin by competing and irreversibly binding to the bacterial cell wall. When this happens, the targeted bacteria cannot produce beta-lactamase and will become susceptible to amoxicillin.

This drug is developed on 1977 by Beecham Research Laboratories in the United Kingdom. The US Patent was applied in 1979.

Uses and common dosages

Co-amoxiclav is given for infections caused by susceptible organisms. These include, but are not limited to the following conditions:

Dosage usually depends on the extent of infection. However, the total daily dose is divided into 3 equal doses given every 8 hours. The drug should not be taken for more than 2 weeks.

  • Mild to moderate infections: 375 milligram tablet every 8 hours
  • Severe infections: 625 milligrams every 8 hours
  • Severe dental infections: 375 milligram tablet every 8 hours for five days
  • Intravenous: 1 gram for 3 to 4 minutes every 8 or 6 hours

For children aged 12 and below, 375 milligram and 625 milligram formulations are not recommended. Those weighing less than 40 kilos are given 20 milligram amoxicillin to 5 milligrams clavulanic acid per kilogram daily in three divided doses. This must not exceed 60 milligrams amoxicillin to 15 milligrams clavulanic acid per kilogram total daily dose. These are usually given suspensions.

Dose adjustment is also applied by prescribers for those with renal impairment. This often depends on the creatinine clearance.

  • Mild (where creatinine clearance is greater than 30 milliliters per minute): No change in dosage.
  • Moderate (when creatinine clearance is between 10 to 30 milliliters per minute): One 375 milligram tablet or one 625 milligram tablet every 12 hours.
  • Severe (if creatinine clearance is less than 10 milliliters per minute): 375 milligram tablets every 24 hours. 625 milligrams are not recommended.

Off label or investigational uses for co-amoxiclav include:

  • Polymicrobial infections of Chlamydia trachomatis
  • Pelvic inflammatory disease
  • Prophylactic antimicrobial for gynecologic surgery

Symptoms of any infection must improve within 48 hours after start of therapy.

Side effects

Like amoxicillin, co-amoxiclav has mild or transitory side effects. Common side effects include:

Treatment must be discontinued when any of these conditions develop:

  • Skin itchiness
  • Reddish rash
  • Blistering and skin peeling
  • Prolonged bleeding time
  • Dizziness
  • Headache

Local irritation, induration, and phlebitis might be observed when co-amoxiclav is administered intravenously.

Precautions and contraindications

Co-amoxiclav is NEVER given to patients with confirmed conditions such as:

  • Severe hepatic impairment
  • Pregnant women, especially in the first trimester
  • Glandular fever as it may form skin rashes

Doctors are also wary of giving this antibiotic to people with the following conditions and may apply dose adjustments:

  • Renal impairment - Dosage depends on the degree of impairment.
  • Gastrointestinal diseases - This may lead to pseudomembranous colitis.
  • Sodium restricted diet - Sodium content of the drug is taken into account especially when high doses are given parenterally (via the veins).
  • Hepatic dysfunction - Liver function tests may be taken periodically.

Interactions and incompatibilities

Co-amoxiclav may also interfere with the following medications:

It may also lead to false positive result with urine glucose and Coombs test.

These should be remembered for parenteral formulations of co-amoxiclav:

  • It must NEVER be mixed with dextrose solution, sodium bicarbonate injectible solution, protein-containing fluids, blood or plasma, and intravenous lipid emulsions. Reconstituted solution may be injected in the drip tubing for 3 to 4 minutes.
  • When given with an aminoglycoside, it should not be mixed in any container or set. This will lose the aminoglycoside's potency.
  • It can be mixed with 10 to 20 milliliters of water for injection depending on the amount of powder for reconstitution. This can further be diluted with the desired volume of parenteral infusion fluids.
  • Reconstituted solutions must be used within 20 minutes. Any unused solution within this time frame must be discarded.


Popular brands in the Philippines are Amoclav ® and Augmentin ®. These are sold under prescription in film coated tablets (in 375 milligrams, 625 milligrams, or 1 gram), suspensions (in 156.25 milligrams, 228.5 milligrams, 312.5 milligrams, or 457 milligrams per 5 milliliters reconstituted), and vials for reconstitution (600 milligrams or 1.2 grams).