A 52-year-old man with type 2 diabetes mellitus for 8 years presents with diabetic macular edema (DME) confirmed on optical coherence tomography (OCT). His best-corrected visual acuity is 6/18. Fundoscopy shows hard exudates in a circinate pattern around the macula. What is the drug of choice for intravitreal injection in this patient?

Explanation

## First-Line Anti-VEGF Therapy for Diabetic Macular Edema **Key Point:** Ranibizumab (Lucentis) is the FDA-approved and gold-standard intravitreal anti-VEGF agent for DME with vision-threatening features. ### Mechanism of Action Ranibizumab is a recombinant humanized monoclonal antibody fragment that binds and neutralizes vascular endothelial growth factor-A (VEGF-A), reducing retinal vascular permeability and edema formation. ### Evidence Base The RESTORE and RISE/RIDE trials demonstrated that ranibizumab monotherapy or combined with laser photocoagulation significantly improves visual acuity and reduces central retinal thickness in DME patients. ### Dosing and Administration - **Intravitreal injection:** 0.5 mg in 0.05 mL - **Frequency:** Monthly for 3 months, then as-needed (PRN) or treat-and-extend (TAE) regimen - **Onset:** Improvement visible within 4 weeks ### Comparison with Other Anti-VEGF Agents | Agent | Approval Status | Indication | Dosing | |-------|-----------------|-----------|--------| | **Ranibizumab** | **FDA-approved for DME** | **DME, BRVO, CRVO** | **0.5 mg monthly or PRN** | | Bevacizumab | Off-label (used in India) | DME, DR | 1.25 mg every 4–6 weeks | | Aflibercept | FDA-approved for DME | DME, BRVO, CRVO | 2 mg every 4 weeks × 3, then every 8 weeks | | Pegaptanib | Older agent | BRVO, CRVO | 0.3 mg every 6 weeks | **High-Yield:** Ranibizumab is the **preferred first-line** agent in developed countries due to robust clinical trial evidence (RESTORE, RISE/RIDE) and FDA approval specifically for DME. **Clinical Pearl:** In resource-limited settings (including India), bevacizumab is often used off-label due to lower cost, but ranibizumab remains the gold standard where available. ### When to Consider Alternatives - **Triamcinolone acetonide:** Reserved for cases with concurrent uveitis or when anti-VEGF fails; causes cataract and glaucoma with repeated use. - **Combination therapy:** Ranibizumab + laser photocoagulation may be superior to either alone in some cases. **Warning:** Do not confuse bevacizumab (Avastin, used off-label) with ranibizumab (Lucentis, FDA-approved for DME). Bevacizumab is a full-length monoclonal antibody; ranibizumab is a smaller fragment with better retinal penetration.