1. Clinical Overview
Ranibizumab is a recombinant humanized monoclonal antibody fragment (Fab) designed for intraocular use. It binds to and inhibits the biological activity of all active forms of human vascular endothelial growth factor A (VEGF-A), a key mediator of angiogenesis and vascular permeability. In the Indian context, it is a critical therapeutic agent for managing neovascular (wet) age-related macular degeneration (AMD), diabetic macular edema (DME), and other retinal vascular disorders, offering a targeted approach to prevent vision loss.
| Onset | Duration | Bioavailability |
|---|---|---|
| Pharmacodynamic effects (reduction in retinal thickness and leakage) can be observed within days, with clinical improvement in visual acuity typically seen within 1-4 weeks after the first injection. | The therapeutic effect is not permanent. The recommended dosing interval is once a month (every 4 weeks) for the initial phase, with maintenance dosing determined by disease activity as assessed by the treating ophthalmologist (often extending to every 1-3 months). | 100% for intraocular administration (intravitreal injection). Systemic bioavailability is negligible (<1%) due to the local route of administration and rapid clearance from systemic circulation. |
2. Mechanism of Action
Ranibizumab is a humanized antigen-binding fragment (Fab) that binds with high affinity to all biologically active isoforms of VEGF-A (e.g., VEGF110, VEGF121, VEGF165). By binding to VEGF-A, it prevents the interaction of VEGF-A with its receptors (VEGFR-1 and VEGFR-2) on the surface of endothelial cells. This inhibition blocks key downstream signaling pathways.
3. Indications & Uses
- Neovascular (Wet) Age-Related Macular Degeneration (AMD)
- Diabetic Macular Edema (DME)
- Macular Edema following Retinal Vein Occlusion (RVO) - Branch RVO (BRVO) and Central RVO (CRVO)
- Choroidal Neovascularization (CNV) due to pathologic myopia (myopic CNV)
4. Dosage & Administration
Adult Dosage: 0.5 mg (0.05 mL of the 10 mg/mL solution) administered by intravitreal injection once a month (every 4 weeks). For wet AMD, DME, and RVO, after the first 3-6 monthly injections, treatment intervals may be extended based on disease activity assessment (e.g., Treat-and-Extend protocol).
Administration: FOR INTRAVITREAL INJECTION ONLY. Administer under strict aseptic technique, including use of sterile gloves, drape, and eyelid speculum. Adequate anesthesia (topical or subconjunctival) and a broad-spectrum topical antiseptic (e.g., 5% povidone-iodine) must be used. The injection is given 3.5-4.0 mm posterior to the limbus (in phakic patients) with a 30-gauge needle. Monitor intraocular pressure and perfusion of the optic nerve head post-injection. Patient must be monitored for at least 30-60 minutes post-procedure for acute elevation of IOP.
5. Side Effects
Common side effects may include:
- Conjunctival hemorrhage
- Eye pain
- Vitreous floaters
- Increased intraocular pressure (transient)
- Foreign body sensation
- Lacrimation increased
- Blurred vision post-injection
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Anti-VEGF Agents (e.g., Aflibercept, Bevacizumab) | Theoretical increased risk of systemic VEGF inhibition effects (hypertension, proteinuria, thromboembolism) if used concurrently. Not recommended. | Major |
| Anticoagulants/Antiplatelets (Warfarin, Clopidogrel, Aspirin) | May increase risk of conjunctival or intraocular hemorrhage during injection. However, these medications are generally NOT discontinued prior to injection due to higher risk of thromboembolic events from stopping them. The ophthalmologist should be aware. | Moderate |
| Antihypertensives | No direct interaction. Important to control BP as hypertension is a risk factor for thromboembolic events. | Minor |
7. Patient Counselling
- Do report any increase in eye pain, redness, sensitivity to light, or worsening vision immediately after injection.
- Do keep your follow-up appointments strictly as scheduled.
- Do inform all your doctors (especially cardiologists/physicians) that you are receiving this injection.
- Don't rub or put pressure on the injected eye.
- Don't miss using the prescribed post-injection antibiotic eye drops.
8. Toxicology & Storage
Overdose: Intraocular overdose could lead to severe increase in intraocular pressure, retinal detachment, or intense intraocular inflammation. Systemic overdose is highly unlikely due to the route and dose.
Storage: Store in a refrigerator at 2°C to 8°C. DO NOT FREEZE. Keep the pre-filled syringe or vial in the outer carton to protect from light. Do not shake. For single use only. Once the vial/syringe is opened, use immediately. Do not use if the solution is discolored or contains particles.