What is the treatment plan for a 29-year-old male with a history of cellulitis of the right foot toe, now presenting with an ingrown toe and worsening pain, and comorbidities including manic bipolar disorder, anxiety, hypertension, long QT syndrome, and obesity?

Treatment Plan for Cellulitis with Suspected Ingrown Toenail

This patient requires immediate re-evaluation with a change in antibiotic therapy to cover both streptococci and Staphylococcus aureus, plus definitive management of the ingrown toenail if present, as the current doxycycline regimen has failed after 1.5 weeks.

Immediate Assessment and Antibiotic Management

Re-evaluate the Cellulitis

• Examine for signs of treatment failure: increasing erythema, warmth, swelling, purulent drainage, or systemic symptoms (fever >38.5°C, tachycardia >110 bpm) 1, 2
• The current doxycycline regimen has failed and requires switching to first-line agents that adequately cover streptococci, which are the most common cause of cellulitis 1, 3

Change Antibiotic Therapy

• Switch to oral cephalexin 500mg four times daily OR dicloxacillin 500mg four times daily as first-line treatment for cellulitis 2, 4
• Alternative: amoxicillin-clavulanate if broader coverage is desired 2
• Avoid continuing doxycycline as monotherapy since it has inadequate activity against β-hemolytic streptococci, which cause the majority of cellulitis cases 1
• Treatment duration: minimum 5 days, but extend if not improved within this timeframe 1, 2, 3

Consider MRSA Coverage

Given this patient's treatment failure and obesity (a risk factor), evaluate for MRSA risk factors 1, 2:

• Add MRSA coverage if: purulent drainage is present, penetrating trauma history, or no improvement after 48 hours on β-lactam therapy 1, 2
• Options for MRSA coverage: add trimethoprim-sulfamethoxazole OR doxycycline to a β-lactam, or use clindamycin alone 1

Important Medication Consideration

• This patient has long QT syndrome: avoid fluoroquinolones and use caution with macrolides (erythromycin, azithromycin) as these can prolong QT interval 4
• Cephalexin is safe in this context 4

Management Based on Ingrown Toenail Status

If Ingrown Toenail IS Present

Definitive surgical management is required as this is a predisposing factor perpetuating the cellulitis 1:

• Refer for partial nail avulsion with phenol matricectomy: This is the most effective treatment, reducing recurrence to 14% compared to 41% with surgery alone 5
• Timing: Can be performed once acute cellulitis is controlled (typically after 48-72 hours of appropriate antibiotics) 5
• Alternative if surgery contraindicated: Orthotic interventions such as toe silicone devices or semi-rigid orthotic devices, though less effective 1

If Ingrown Toenail is NOT Present

Address underlying predisposing factors aggressively to prevent recurrent cellulitis 1, 6:

• Treat toe web abnormalities: Examine for and treat tinea pedis or interdigital maceration with topical antifungals 1
• Manage obesity: Weight loss counseling, as obesity significantly increases recurrence risk 1, 6
• Optimize venous insufficiency: Consider compression stockings if venous disease present 1
• Foot hygiene education: Keep skin well-hydrated with emollients to prevent cracking; proper foot care 1, 7

Adjunctive Measures (Both Scenarios)

• Elevate the affected foot above heart level to promote drainage of edema and inflammatory substances 1, 2
• Monitor blood pressure closely given his hypertension and the inflammatory state 1
• Avoid systemic corticosteroids in this patient as they are only weakly recommended for non-diabetic patients and his multiple comorbidities increase risk 1

Follow-Up Protocol

• Re-evaluate within 48-72 hours to assess response to new antibiotic therapy 2
• If no improvement after 48 hours: Consider adding MRSA coverage, evaluate for deeper infection, or consider imaging to rule out abscess 1, 2, 3
• If 3-4 episodes occur per year despite addressing risk factors: Consider prophylactic antibiotics (oral penicillin V 1g twice daily or erythromycin 250mg twice daily for 4-52 weeks) 1

Critical Pitfalls to Avoid

• Do not continue doxycycline monotherapy for non-purulent cellulitis as it lacks adequate streptococcal coverage 1
• Do not ignore the ingrown toenail if present—it will perpetuate recurrent infections and must be definitively treated 1
• Do not prescribe fluoroquinolones given his long QT syndrome 4
• Do not delay surgical referral for ingrown toenail once cellulitis is controlled, as conservative management has high failure rates 5