1. First-Line Agents

Systemic corticosteroids and high-dose antivirals are the foundation of initial therapy, targeting the underlying immune-mediated inflammation and potential viral triggers, respectively.

Systemic Corticosteroids

• Mechanism: Inhibit NF-κB and other transcription factors, leading to a broad reduction in proinflammatory cytokines (e.g., TNF-α, IL-1, IL-6).
• Indications: EM major with extensive mucosal ulceration, significant systemic symptoms (fever, malaise), or evidence of organ involvement.
• Agent Selection: Intravenous (IV) methylprednisolone is preferred for rapid onset in critically ill patients. Transition to oral (PO) prednisone for tapering once clinical stability and GI function are established.
• Dosing: Pulse-dose methylprednisolone 1 g IV daily for 3 days, followed by a prednisone taper starting at 1 mg/kg/day PO over 4–6 weeks.
• PK/PD in Critical Illness: Sepsis and capillary leak can increase the volume of distribution (Vd). Hypoalbuminemia can increase the free, active fraction of the drug. Dosing should be guided by clinical response rather than strict nomograms.
• Monitoring: Blood glucose every 6 hours, daily complete blood count (CBC) with differential, and procalcitonin to monitor for secondary infections.

High-Dose Antivirals

• Mechanism: Inhibits viral DNA polymerase, preventing replication of herpes simplex virus (HSV), a common trigger for recurrent EM.
• Indications: Confirmed or highly suspected HSV-associated EM, or as empiric therapy in patients with a history of recurrent oral or genital herpes.
• Dosing: Acyclovir 10–15 mg/kg IV every 8 hours. Dose must be adjusted for renal impairment (e.g., reduce by 50% for patients on continuous veno-venous hemofiltration [CVVH]).
• Monitoring: Serum creatinine daily. Monitor neurologic status for signs of neurotoxicity (confusion, myoclonus), especially in renal failure.

2. Second-Line and Adjunctive Therapies

When first-line agents are contraindicated, ineffective, or insufficient, intravenous immunoglobulin (IVIG) and cyclosporine offer alternative mechanisms of immunomodulation.

Intravenous Immunoglobulin (IVIG)

• Mechanism: Multifactorial, including blockade of Fc receptors on phagocytes, neutralization of pathogenic autoantibodies and complement, and suppression of inflammatory cytokines.
• Indications: Steroid-refractory EM major; cases with significant epidermal detachment overlapping with Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN).
• Dosing: Total dose of 2 g/kg administered over 2–5 days (e.g., 0.4 g/kg/day for 5 days).
• Monitoring: Renal function (BUN/SCr) daily. Assess for thromboembolic risk and monitor for infusion-related reactions (hypotension, rigors).

Cyclosporine

• Mechanism: Calcineurin inhibitor that blocks the transcription of IL-2, thereby inhibiting the activation and proliferation of T-cells.
• Indications: Refractory EM major, particularly when IVIG is contraindicated, unavailable, or has failed.
• Dosing: 3–5 mg/kg/day, given PO or IV in two divided doses. Therapeutic drug monitoring is mandatory.
• Monitoring: Target trough levels of 100–200 ng/mL. Monitor blood pressure every 4 hours and serum creatinine daily. Be vigilant for drug interactions (e.g., azole antifungals, macrolides).

3. Pharmacokinetic (PK) and Pharmacodynamic (PD) Adjustments in Organ Dysfunction

Critical illness profoundly alters drug disposition. Dosing must be adapted to account for sepsis-induced capillary leak, renal replacement therapy (RRT), and hypoalbuminemia.

• Increased Volume of Distribution (Vd): Capillary leak and aggressive fluid resuscitation can increase Vd, potentially requiring higher loading doses for some medications to achieve therapeutic concentrations quickly.
• Decreased Protein Binding: In hypoalbuminemia (albumin < 2.5 g/dL), the free (active) fraction of highly protein-bound drugs like cyclosporine increases, raising the risk of toxicity. Dose reductions of 25-50% may be necessary.
• Renal Replacement Therapy (RRT):
  • Acyclovir: Significantly cleared by both intermittent hemodialysis and continuous therapies. Reduce maintenance dose by at least 50% on CVVH and consider post-filter supplementation.
  • Methylprednisolone: Negligible removal by dialysis; no dose adjustment needed.
  • Cyclosporine: High molecular weight and protein binding prevent significant clearance; monitor troughs, but dose adjustments are not typically required for RRT itself.

4. Route of Administration and Device Considerations

Ensuring reliable drug delivery is critical. IV administration is standard initially, with a planned transition to enteral routes as the patient stabilizes.

IV to Oral Conversion

Transition from IV to PO therapy once the patient is hemodynamically stable, tolerating enteral nutrition, and showing clinical improvement. A common conversion is from IV methylprednisolone to PO prednisone (approximate potency ratio is 1 mg IV methylprednisolone to 1.25 mg PO prednisone).

Enteral Tube Administration

When using feeding tubes, prefer liquid or suspension formulations. If only tablets are available, ensure they can be crushed. Flush the tube with at least 15-30 mL of water before and after administration to ensure full delivery and prevent clogging.

Device Tips

Administer hyperosmolar or vesicant infusions like high-dose acyclovir or IV cyclosporine through a central venous catheter to minimize risk of phlebitis and extravasation. Always label lines clearly to prevent medication errors.

5. Monitoring Efficacy and Safety

A structured monitoring plan is essential to guide therapy, allowing for timely escalation for non-responders and de-escalation to minimize adverse effects.

Efficacy Endpoints

• Cessation of new lesion formation (target: within 48-72 hours of therapy initiation).
• Progression of mucosal healing and re-epithelialization.
• Reduction in pain scores, assessed every 8 hours.
• Use of daily digital photography to objectively document skin changes.

Safety Surveillance

• Hyperglycemia: Capillary blood glucose checks every 6 hours; initiate insulin protocol as needed.
• Infection: Daily monitoring of WBC count, temperature, and procalcitonin.
• Renal Function: Daily serum creatinine to detect nephrotoxicity and guide dose adjustments.
• Neurotoxicity: Daily neurologic checks (level of consciousness, myoclonus) for patients on high-dose acyclovir.

6. Pharmacoeconomics and Resource Utilization

Drug acquisition costs must be balanced against the potential for clinical benefit and impact on ICU length of stay.

• Corticosteroids: Low acquisition cost (<$5/day for prednisone). Early, effective use may shorten ICU stay, leading to significant overall savings.
• Acyclovir: Moderate cost (~$150/day for IV formulation). Cost-effective if it prevents recurrent HSV flares that would prolong hospitalization.
• IVIG: High acquisition cost (>$2,500 per course). Its use should be reserved for severe, refractory cases where the potential benefit justifies the expense.
• Cyclosporine: Moderate drug cost (~$50/day) but requires additional resources for therapeutic drug monitoring.

7. Clinical Decision Algorithm

A structured pathway ensures timely initiation, escalation, and de-escalation of therapy based on clinical response and toxicity.