In this article, we will learn about the indications, contraindications and dosage, as well as drug interactions for each of the Amoxicillin and Ampicillin

Amoxicillin and Ampicillin in detail

Amoxicillin (Amoxil) in detail

Description of Amoxicillin

A broad spectrum beta-lactam antibacterial.

Indications of Amoxicillin

Used to treat bacterial infection such as a dental abscess. Used pro-phylactically in the prevention of infective endocarditis.

Presentations of Amoxicillin

Capsules of 250 mg and 500 mg.
500 mg dispersible tablets.
Oral suspensions of 125 mg/5 mL and 250 mg/5 mL.
Powder for reconstitution for oral administration 750 mg and 3 g.
250 mg and 500 mg vials for reconstitution for injection.

Dose of Amoxicillin

For management of dental infections
250–500 mg orally three times daily for out-patient treatment.
500–1000 mg intravenously four times daily for severe infections.
Child under 10 years: 50% adult dose.
For prophylaxis of infective endocarditis.
3 g orally one hour preoperatively for prophylaxis when treatment under local anaesthesia. Under general anaesthesia 1 g intrave-nously or intramuscularly at induction followed by 500 mg 6 hours later: or 3 g orally 4 hours preoperatively followed by 3 g orally as soon as practicable after surgery.
Child under 5 years: 25% adult dose.
Child 5–10 years 50% adult dose.

Contraindications of Amoxicillin

Hypersensitivity
Precautions
Renal disease.
Glandular fever.
Chronic lymphatic leukaemia.
HIV.

Unwanted effects of Amoxicillin

Glossitis and tongue discolouration.
Candidiasis.
Hypersensitivity.
Gastrointestinal upset.
Pseudomembranous colitis.
Hypokalaemia.
Drug interactions
Amoxicillin reduces the excretion of the cytotoxic drug methotrexate,
leading to increased toxicity of the latter drug which may cause death.
There may be a reduced efficacy of oral contraceptives and other
methods of contraception are advised during antibiotic therapy.
Amoxicillin activity is decreased by tetracyclines. Amoxicillin rarely
increases the prothrombin time when given to patients receiving war-farin. Probenecid significantly increases the half-life of amoxicillin.
Nifedipine increases amoxicillin absorption but this is of little clinical
importance. Amiloride decreases the absorption of amoxicillin but this
is probably of little significance. The production of rashes is increased
during concomitant treatment with allopurinol.

Ampicillin (Penbritin)

Description of Ampicillin

A broad spectrum beta-lactam antibacterial.

Indications of Ampicillin

Used to treat bacterial infection such as a dental abscess.

Presentations of Ampicillin

250 mg and 500 mg capsules.
Syrup with 125 mg/5 mL and 250 mg/5 mL.
Oral suspensions of 125 mg/1.25 mL, 125 mg/5 mL and 250 mg/ 5 mL.
250 mg and 500 mg vials for reconstitution for injection.
Also available in combination with cloxacillin as Ampiclox.

Dose of Ampicillin

250–1000 mg four times daily.
Child under 10 years: 50% adult dose.

Contraindications of Ampicillin

Hypersensitivity.
Precautions
Renal disease.
Glandular fever.
Chronic lymphatic leukaemia.
HIV.

Unwanted effects of Ampicillin

Glossitis and tongue discolouration.
Candidiasis.
Hypersensitivity.
Stevens–Johnson syndrome.
Gastrointestinal upset.
Hypokalaemia.
Pseudomembranous colitis.
Drug interactions
Ampicillin reduces the excretion of the cytotoxic drug methotrexate,
leading to increased toxicity of the latter drug which may cause
death. There may be a reduced efficacy of oral contraceptives and
other methods of contraception are advised during antibiotic ther- apy. Ampicillin activity is decreased by tetracyclines. Antagonism
also occurs with chloramphenicol and the neurological side effects of
the latter drug (e.g. deafness) are increased during combined ther-
apy. Chloroquine reduces the absorption of ampicillin. Ampicillin
rarely increases the prothrombin time when given to patients receiv-ing warfarin. Ampicillin can increase the muscle weakness of patients with myasthenia gravis who are receiving anti-cholinergic drugs.

Ampicillin reduces the efficacy of sulphasalazine which is used in the
treatment of Crohn’s disease.
Probenecid significantly increases the half-life of ampicillin.
Nifedipine increases ampicillin absorption but this is of little clinical
importance. Amiloride decreases the absorption of ampicillin but this is probably of little significance. The production of rashes is increased during concomitant treatment with allopurinol. Large single doses of ampicillin (1 g) decrease the serum levels of the anti-hypertensive drug atenolol by half.

resources and references
The Dentist’s Drug and Prescription Guide
Mea Weinberg and Stuart J. Froum
Stuart L. Segelnick, Consulting Editor