What is the recommended workup and treatment for a patient with intravenous (IV) drug use and cellulitis myositis?

From the Guidelines

The recommended workup for a patient with IV drug use and cellulitis/myositis includes blood cultures, complete blood count, basic metabolic panel, C-reactive protein, and imaging (ultrasound or MRI) to assess the extent of infection, as well as empiric antibiotic therapy with coverage for MRSA, streptococci, and gram-negative organisms, such as vancomycin 15-20 mg/kg IV every 8-12 hours plus piperacillin-tazobactam 4.5g IV every 6-8 hours, as suggested by the Infectious Diseases Society of America guidelines 1. The choice of antibiotics should be guided by the severity of the infection and the presence of systemic signs of infection, with vancomycin or another antimicrobial effective against both MRSA and streptococci recommended for patients with severe nonpurulent infections or those associated with penetrating trauma, evidence of MRSA infection elsewhere, nasal colonization with MRSA, injection drug use, or SIRS 1. Some key points to consider in the management of these patients include:

• The importance of addressing pain management, providing tetanus prophylaxis if indicated, screening for HIV/hepatitis, and considering addiction medicine consultation for substance use disorder treatment.
• The need for close follow-up within 24-48 hours to assess treatment response and adjust the antibiotic regimen as necessary.
• The potential for polymicrobial infections in IV drug users, including MRSA, which is particularly prevalent in this population, and the need for broad-spectrum antibiotic coverage.
• The role of surgical consultation in patients with evidence of abscess, compartment syndrome, or necrotizing infection, as well as the potential need for incision and drainage or debridement in these cases 1. The treatment duration typically ranges from 7-14 days, depending on clinical response, with possible transition to oral antibiotics once improvement occurs, as recommended by the Infectious Diseases Society of America guidelines 1.

From the FDA Drug Label

The majority of cases were subsequently categorized as complicated cellulitis, major abscesses, or traumatic wound infections. Adult patients with clinically documented complicated skin and skin structure infections (cSSSI) were enrolled in two randomized, multinational, multicenter, investigator-blinded trials comparing daptomycin for injection (4 mg/kg IV q24h) with either vancomycin (1 g IV q12h) or an anti-staphylococcal semi-synthetic penicillin (i.e., nafcillin, oxacillin, cloxacillin, or flucloxacillin; 4 to 12 g IV per day).

The recommended workup for a patient with intravenous (IV) drug use and cellulitis myositis includes:

• Clinical evaluation for signs and symptoms of complicated skin and skin structure infections (cSSSI)
• Laboratory tests to identify the causative pathogen
• Imaging studies to assess the extent of the infection

The recommended treatment for a patient with IV drug use and cellulitis myositis includes:

• Antibiotic therapy: daptomycin for injection (4 mg/kg IV q24h) or vancomycin (1 g IV q12h) or an anti-staphylococcal semi-synthetic penicillin (i.e., nafcillin, oxacillin, cloxacillin, or flucloxacillin; 4 to 12 g IV per day)
• Supportive care: wound care, pain management, and monitoring for complications 2 2 2

From the Research

Workup for IV Drug Use and Cellulitis Myositis

• The workup for a patient with intravenous (IV) drug use and cellulitis myositis should include a comprehensive evaluation to confirm the etiology of the infection, as suggested by current diagnostic and treatment guidelines 3.
• This evaluation may involve blood, urine, and sputum cultures to identify the causative pathogen and determine the appropriate antibiotic therapy.
• It is essential to consider the patient's history of IV drug use, as this population is at increased risk of infections, particularly those caused by Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) 4.

Antibiotic Therapy

• The choice of empiric antibiotic therapy should be based on the likely etiologies and anticipated resistance patterns, taking into account the patient's history of IV drug use and recent antibiotic use 3.
• For patients with cellulitis, initial empiric broad-spectrum antibiotic therapy may be necessary, with subsequent tailoring of therapy based on culture and susceptibility test results 3.
• Oral antibiotics such as penicillin, amoxicillin, and cephalexin may be sufficient for non-purulent, uncomplicated cases of cellulitis caused by β-hemolytic streptococci or methicillin-sensitive Staphylococcus aureus 5.
• However, for patients with more severe infections or those who have received antibiotics prior to trial entry, intravenous (IV) antibiotic therapy may be preferred 6.

Route and Duration of Antibiotic Therapy

• The route of antibiotic administration (IV or oral) may not significantly impact the clinical outcome for patients with cellulitis of similar severity 6.
• The duration of antibiotic therapy may also not be associated with the clinical outcome, and a course length of > 5 days may not result in additional benefit 6.
• For patients with methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia, nafcillin or cefazolin may be more effective than vancomycin, with lower mortality hazards 7.