What is Dicloxacillin (antibiotic)?

From the Guidelines

Dicloxacillin is recommended as the oral agent of choice for methicillin-susceptible strains in adults, at a dose of 500 mg qid po, for the treatment of skin and soft tissue infections, including impetigo and MSSA SSTI, as per the guidelines from the Infectious Diseases Society of America 1.

Key Points

• Dicloxacillin is a penicillin-class antibiotic effective against penicillinase-producing staphylococci.
• The recommended dose for adults is 500 mg orally every 6 hours, with pediatric dosing at 25–50 mg/kg/d in 4 divided doses po, although it is not commonly used in pediatrics.
• The standard treatment duration is 7-10 days, but may be longer for complicated infections.
• Common side effects include gastrointestinal disturbances, and patients should complete the full course of treatment.
• Dicloxacillin works by inhibiting bacterial cell wall synthesis and is particularly useful for skin and soft tissue infections where staphylococcal resistance is a concern.

Considerations

• Patients with penicillin allergy should avoid this medication and inform their healthcare provider of any adverse reactions.
• Dicloxacillin should be taken on an empty stomach to maximize absorption.
• Alternative antibiotics, such as cephalexin or clindamycin, may be considered for patients with penicillin allergy or in cases where dicloxacillin is not effective, as recommended by the guidelines from the Infectious Diseases Society of America 1.

Dosage and Administration

• Adults: 500 mg qid po
• Pediatrics: 25–50 mg/kg/d in 4 divided doses po
• Take on an empty stomach, 1 hour before or 2 hours after meals, to maximize absorption.

From the FDA Drug Label

The penicillinase-resistant penicillins are indicated in the treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drugs. To reduce the development of drug-resistant bacteria and maintain the effectiveness of dicloxacillin sodium capsules and other antibacterial drugs, dicloxacillin sodium capsules should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria The main use of dicloxacillin is to treat infections caused by penicillinase-producing staphylococci that are susceptible to the drug 2.

• Dicloxacillin should only be used to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria 2. Key points:
• Dicloxacillin is a penicillinase-resistant antibiotic 2
• It should not be used in infections caused by organisms susceptible to penicillin G 2

From the Research

Dicloxacillin Overview

• Dicloxacillin is a semisynthetic isoxazolyl penicillin that exhibits antimicrobial activity against a wide variety of Gram-positive bacteria, as well as stability against penicillinases and low level of toxicity 3.
• It is used to treat infections caused by Staphylococcus aureus, including methicillin-susceptible S. aureus (MSSA) infections 4.

Antibacterial Activity

• Dicloxacillin has significant antibacterial activity against MSSA, coagulase-negative Staphylococcus (CNS), and other Streptococcus isolates 3.
• However, it shows poor antibacterial activity against Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae 3.
• Resistance to dicloxacillin was observed in 7.5% of CNS isolates and 9.2% of other Streptococcus isolates, whereas 1.5% of MSSA was resistant to dicloxacillin 3.

Dosage Regimens

• The simulation results suggest that dicloxacillin 250 mg every 6 hours (q6h) and 500 mg q6h dosing regimens may be recommended for clinical applications, especially for community-onset infections 3.
• Multiple-dose regimens could obtain higher cumulative fraction of response (CFR) than single-dose regimens against H. influenzae and S. pneumoniae 3.
• All dosing regimens against MSSA achieved CFR ≥90% 3.

Comparison with Other Antibiotics

• Dicloxacillin was compared with cephalexin in a randomly controlled study for the treatment of staphylococcal skin and skin structure infections, and both antibiotics proved equally effective 5.
• Cephalexin and dicloxacillin are both effective against staphylococcal infections, but cephalexin can be given twice daily, which may enhance compliance 5.
• Other antibiotics, such as erythromycin, clindamycin, and metronidazole, may also be used to treat various infections, including those caused by Staphylococcus aureus 4, 6, 7.