From the Guidelines
For treating methicillin-sensitive Staphylococcus aureus (MSSA) infections orally, first-line options include dicloxacillin 500 mg four times daily, cephalexin 500 mg four times daily, or clindamycin 300-450 mg three times daily for 7-14 days, depending on infection severity, as recommended by the most recent guidelines 1. The choice of antibiotic should be based on the severity of the infection, patient allergies, and local resistance patterns.
- Dicloxacillin and cephalexin are beta-lactam antibiotics that target the bacterial cell wall, while clindamycin targets protein synthesis.
- For patients with penicillin allergies, clindamycin is preferred, or trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily can be used, as suggested by the guidelines 1.
- Doxycycline 100 mg twice daily is another alternative, although its use is limited by resistance patterns and patient age, as noted in the guidelines 1. Treatment duration varies by infection type:
- 5-7 days for uncomplicated skin infections
- 10-14 days for cellulitis or deeper infections
- Potentially longer for complicated infections like osteomyelitis, as recommended by the guidelines 1. It's essential to complete the full course of antibiotics even if symptoms improve quickly and to follow up if symptoms worsen or don't improve within 48-72 hours, as this may indicate treatment failure or need for intravenous therapy, as emphasized by the guidelines 1.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION The penicillinase-resistant penicillins are available for oral administration and for intramuscular and intravenous injection. The sodium salts of cloxacillin, dicloxacillin, oxacillin, and nafcillin are available for oral use Bacteriologic studies to determine the causative organisms and their sensitivity to the penicillinase-resistant penicillins should always be performed.
Metabolism In vitro studies in human liver and intestinal microsomes indicated that clindamycin is predominantly metabolized by Cytochrome P450 3A4 (CYP3A4), with minor contribution from CYP3A5, to form clindamycin sulfoxide and a minor metabolite, N- desmethylclindamycin. Antimicrobial Activity Clindamycin has been shown to be active against most of the isolates of the following microorganisms, both in vitro and in clinical infections [see Indications and Usage (1)]: Gram-positive bacteria Staphylococcus aureus (methicillin-susceptible strains)
Oral antibiotic choices for MSSA include:
- Dicloxacillin
- Clindamycin
These antibiotics are effective against Methicillin-Susceptible Staphylococcus aureus (MSSA), as indicated by the drug labels 2 and 3.
From the Research
Oral Antibiotic Choices for MSSA
- The choice of oral antibiotics for methicillin-susceptible Staphylococcus aureus (MSSA) infections depends on the severity of the infection and patient factors such as penicillin hypersensitivity 4.
- For less serious MSSA infections, such as skin and soft tissue infections, first-generation cephalosporins (e.g., cefazolin, cephalexin), clindamycin, lincomycin, and erythromycin may be used 4.
- Cefazolin has been shown to be effective in treating MSSA infections complicated by bacteremia, with a lower risk of mortality compared to nafcillin or oxacillin 5.
- Ceftriaxone, a once-daily antibiotic, has been evaluated as a potential treatment option for MSSA infections, with some studies suggesting it may be associated with a lower risk of toxicity requiring therapy alteration compared to antistaphylococcal antibiotics (ASAs) 6.
- A comparative review of cefazolin versus antistaphylococcal penicillins for MSSA bacteremia found that cefazolin offers several pharmacologic advantages, including more convenient dosing regimens, and may be considered as a first-line therapy for MSSA infections 7.
Specific Antibiotic Options
- Cefazolin: effective in treating MSSA infections complicated by bacteremia, with a lower risk of mortality compared to nafcillin or oxacillin 5.
- Ceftriaxone: may be associated with a lower risk of toxicity requiring therapy alteration compared to ASAs, but its efficacy compared to ASAs is unclear 6.
- Clindamycin: may be used for less serious MSSA infections, such as skin and soft tissue infections 4.
- Erythromycin: may be used for less serious MSSA infections, such as skin and soft tissue infections, but its use is limited by resistance 4.
Considerations
- Patient factors, such as penicillin hypersensitivity, should be considered when choosing an oral antibiotic for MSSA infections 4.
- The severity of the infection and the presence of complicating factors, such as bacteremia, should also be considered when choosing an oral antibiotic for MSSA infections 5.
- The potential for resistance and the need for antimicrobial stewardship should be considered when choosing an oral antibiotic for MSSA infections 7.