Brentclox Uses, Dosage, Side Effects and Composition

Description and composition of Brentclox

Brentclox is a fixed dose combination antibacterial antibiotic with broad spectrum of activities.

It contains Ampicillin and cloxacillin as its active ingredients. These two active ingredients belong to Penicillin antibiotic.

They come in different dosage forms but capsules and powder for suspension are the most common of them. The common strength of the combination is 250mg and 500mg. In these strengths, the combination has 1:1 ratio of each.

Pharmacology of Brentclox

Ampicillin, an amino-penicillin and cloxacillin, an isoxazolyl penicillin have an identical mode of action i.e., they inhibit bacterial cell wall synthesis.

This results in the weakening of the bacterial cell wall and cell lysis. Ampicillin is susceptible to degradation by B-lactamases and is therefore inactive against strains producing this enzyme.

The combination displays synergy against some ß-lactamase producing organisms as cloxacillin protects ampicillin from enzymatic destruction by B-lactamases by binding them.

Most staphylococci and many strains of E.coli, H. influenzae, M. catarrhalis, N.gonorrhoeae, Salmonella and Shigella are resistant to ampicillin as beta-lactamases produced by these strains inactivate ampicillin.

Cloxacillin forms a relatively stable enzyme substrate complex with beta-lactamase and competitively inhibits the activity of beta-lactamases; thus cloxacillin when given in combination with ampicillin protects the latter from the destruction by beta-lactamase.

The sparing of ampicillin by this mechanism increases the availability of ampicillin at the site of infection. This serves to retain the broad antibacterial spectrum of ampicillin against Gram-positive as well as Gram-negative organisms including those that produce beta-lactamase.

Uses of Brentclox

Brentclox is used for the treatment of infections of the respiratory tract, ear, nose and throat (ENT), urinary tract, gastro-intestinal tract, skin and soft-tissue; Septicaemia, pelvic infections, endocarditis and orthopaedic infections.

Dosage of Brentclox

Adult dosage

By mouth,

  • 0.5-1 g 6 hourly or more frequently according to the severity of the infection.

By IM Injection,

  • 0.5-1 g 6 hourly By IV Injection, 0.5-1 g 4-6 hourly; up to 12 g by IV infusion

Neoplasms of the salivary gland (secondary bacterial infections):

  • 250/250 mg every 6 hours for 5-7days


  • 500 mg – 1 g by mouth every 6 hours for 5-7 days.

Child dosage

Child (1 month-2 years): by mouth,

  • ¼ adult dose; 2-10 years, ½ adult dose.

Neonate: Oral drops

  • 0.6 mL (90 mg) 4 hourly.
  • By IV Injection, 75 mg 8 hourly
  • By IM Injection, 75 mg 8 hourly


  • Child (<5 years): 25% of adult dose;
  • 5- 10 years: 50% of adult dose

Side effects of Brentclox

The following are common side effects associated with the use of Ampicillin & Cloxacillin combination:

  • Gastrointestinal reactions such as nausea, vomiting, diarrhoea, pseudomembranous colitis, cholestatic jaundice
  • Neutropenia; anaphylaxis, serum sickness-like reactions, skin rash, hives, itching
  • Oral candidiasis

Drugs interactions with Brentclox

  • Bacteriostatic antibiotics such as tetracyclines, erythromycin or sulphonamides may antagonize the bactericidal effect of penicillin. For this reason, do not give them together (avoid co-administration).
  • Probenecid decreases renal tubular secretion of penicillins resulting in increased and more prolonged penicillin concentrations.
  • Allopurinol: increased incidence of skin rash).
  • Oral contraceptives: decreased efficacy of oral contraceptives due to reduction in enterohepatic circulation of oestrogens.
    • Advise patient to use alternative or additional method of contraception while taking ampicillin).


Brentclox is contraindicated in history of hypersensitivity to penicillins, cephalosporins, penicillin derivatives or penicillamine.


Take precautions when any of the following conditions is true

  • History of gastrointestinal disease especially antibiotic associated colitis (ampicillin like other penicillins may cause pseudomembranous colitis).
  • Renal impairment
  • Infectious mononucleosis: May cause skin rash in patients with infectious mononucleosis.

Recommendations on the use of Brentclox in  Pregnancy and Lactation

Ampicillin, like other penicillins, is considered low risk at all stages of pregnancy

Ampicillin is excreted into breast milk. Though considered compatible with breastfeeding, its use has been associated with modification of the bowel flora and allergic response or sensitization in the breastfeeding infant.


For Oral, Intramuscular or Intravenous administration. Administer orally on an empty stomach (i.e., 1 hour prior to, or 2 hours after meals) to increase total absorption; with a full glass of water.

Shake suspension well before each dose. Avoid IM or IV use except in severe infection or when patient can’t take oral dose. Give IV intermittently to prevent vein irritation.

Mix with sterile water and give directly IV; alternatively, mix with 0.9% NS; solutions for IV infusion will be inactivated by dextrose at room temperature.

Administer around-the-clock (in equal interval) rather than 4 times/day to promote less variation in peak and trough serum levels.

Ampicillin and gentamicin should not be mixed in the same IV tubing or administered concurrently.

How to store

Store below 25°C. Protect from moisture and light.

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