From the Guidelines
No, dicloxacillin and nafcillin are not the same medication, though they are related, as indicated by the most recent guidelines from 2014 1. Both are penicillinase-resistant penicillins used to treat infections caused by susceptible gram-positive bacteria, particularly Staphylococcus aureus, including methicillin-sensitive strains. The key difference is in their administration routes:
- Dicloxacillin is primarily given orally, with a recommended dosage of 500 mg qid po for adults and 25–50 mg/kg/d in 4 divided doses po for children, as stated in the 2014 guidelines 1.
- Nafcillin is administered intravenously or intramuscularly, with a recommended dosage of 1-2 g every 4 h IV for adults and 100–150 mg/kg/d in 4 divided doses for children, according to the same guidelines 1. They have similar antimicrobial spectrums but differ slightly in their pharmacokinetic properties. Dicloxacillin typically has better oral absorption and is often used for less severe infections that can be treated on an outpatient basis. Nafcillin, being parenteral, is generally reserved for more serious infections requiring hospitalization. Both medications can cause similar side effects including allergic reactions, gastrointestinal disturbances, and rarely, liver function abnormalities. Patients allergic to one penicillin should avoid both medications due to cross-reactivity. It's worth noting that while an older study from 2005 1 also discusses the use of dicloxacillin and nafcillin, the more recent guidelines from 2014 1 take precedence in guiding clinical practice. Therefore, the choice between dicloxacillin and nafcillin should be based on the severity of the infection, the need for outpatient versus inpatient treatment, and the patient's ability to tolerate oral versus parenteral therapy, as recommended by the most recent guidelines 1.
From the FDA Drug Label
The sodium salts of methicillin, oxacillin, and nafcillin may be administered parenterally and the sodium salts of cloxacillin, dicloxacillin, oxacillin, and nafcillin are available for oral use
- Dicloxacillin and nafcillin are both penicillinase-resistant penicillins.
- They are used to treat similar types of infections, such as staphylococcal infections.
- However, the FDA drug label does not provide a direct comparison of their efficacy or equivalence.
- Key differences include their administration routes and formulations: dicloxacillin is available for oral administration, while nafcillin is available for intravenous injection.
- In summary, while dicloxacillin and nafcillin share some similarities, they are not the same medication, and their usage should be determined based on individual patient needs and clinical judgment 2.
From the Research
Comparison of Dicloxacillin and Nafcillin
- Dicloxacillin and nafcillin are both penicillinase-resistant penicillins, which are effective against Staphylococcus aureus infections 3, 4.
- According to a study published in the American journal of hospital pharmacy, there are no important differences in therapeutic effect among oxacillin, cloxacillin, dicloxacillin, or flucloxacillin by the oral route, or among oxacillin, dicloxacillin, nafcillin, or methicillin parenterally 4.
- This suggests that dicloxacillin and nafcillin have similar therapeutic effects, although they may have different pharmacokinetic properties, such as absorption and protein binding 5.
- The choice of antibiotic depends on various factors, including the severity of the infection, the presence of resistance, and the patient's medical history and allergies 3, 4.
Key Differences
- Dicloxacillin is typically administered orally, while nafcillin is usually given parenterally 4, 5.
- The extent of protein binding and serum levels of dicloxacillin and nafcillin may differ, which can affect their efficacy and duration of action 5.
- However, there is no conclusive evidence to suggest that one is more effective than the other in treating Staphylococcus aureus infections 3, 4, 5.