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 |
|---|---|---|
| Rapid, with detectable VEGF inhibition within the eye post-injection. Clinical effects on macular edema and hemorrhage are typically observed within days to a week. | Approximately 1 month. The therapeutic effect wanes over time, necessitating repeated intravitreal injections as per treatment regimen (monthly or as needed). | 100% intraocular bioavailability following intravitreal injection. Systemic bioavailability is negligible (<1%). |
2. Mechanism of Action
Ranibizumab is a 48 kDa antigen-binding fragment (Fab) derived from the same parent mouse antibody as bevacizumab. It is affinity-matured to provide stronger binding to VEGF-A. By binding with high affinity to all biologically active isoforms of VEGF-A (e.g., VEGF110, VEGF121, VEGF165), it prevents VEGF-A from interacting with its receptors (VEGFR-1 and VEGFR-2) on the surface of endothelial cells. This inhibition blocks key downstream signaling pathways that lead to endothelial cell proliferation, angiogenesis (new blood vessel formation), and vascular hyperpermeability (leakage).
3. Indications & Uses
- Neovascular (Wet) Age-related Macular Degeneration (AMD)
- Diabetic Macular Edema (DME)
- Macular Edema following Retinal Vein Occlusion (Branch RVO or Central RVO)
4. Dosage & Administration
Adult Dosage: 0.5 mg (0.05 mL of the 10 mg/mL solution) administered by intravitreal injection once a month. For wet AMD, after the first 3 monthly injections, treatment interval may be individualized (e.g., treat-and-extend or pro re nata (PRN) based on disease activity as assessed by OCT and visual acuity). For DME and RVO, monthly dosing is typically initiated, with potential for individualization after initial period.
Administration: FOR INTRAVITREAL USE ONLY. Administer under strict aseptic conditions, including use of sterile gloves, drape, and eyelid speculum. Adequate anesthesia (topical or subconjunctival) and a broad-spectrum topical antimicrobial agent are required pre-injection. The injection is given 3.5-4.0 mm posterior to the limbus (in phakic patients) into the vitreous cavity. Monitor intraocular pressure (IOP) and perfusion of the optic nerve head post-injection. Patient must be monitored for signs of endophthalmitis.
5. Side Effects
Common side effects may include:
- Conjunctival hemorrhage (subconjunctival bleeding)
- Eye pain
- Vitreous floaters
- Increased intraocular pressure (IOP) immediately post-injection
- Foreign body sensation in eyes
- Lacrimation increased
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Anti-VEGF Agents (e.g., Aflibercept, Bevacizumab) | Theoretical increased risk of ocular or systemic adverse effects. Concomitant use in the same eye is not recommended. | Major |
| Anticoagulants/Antiplatelets (e.g., Warfarin, Clopidogrel, Aspirin) | May increase risk of conjunctival or intraocular hemorrhage during injection. However, these medications should NOT be discontinued routinely as the risk of thromboembolic events outweighs the bleeding risk. Inform the ophthalmologist. | Moderate |
| Topical Ocular Steroids (e.g., Prednisolone acetate) | May be used concomitantly to manage post-injection inflammation. No known pharmacokinetic interaction. | Minor |
7. Patient Counselling
- DO report any eye pain, redness, sensitivity to light, vision changes, or increase in floaters immediately after injection.
- DO use prescribed topical antibiotic drops before and after the procedure as directed.
- DO keep your follow-up appointments strictly.
- DON'T rub or put pressure on the injected eye.
- DON'T swim or use hot tubs for at least 3-4 days post-injection to reduce infection risk.
- DON'T miss informing your ophthalmologist about all your medications, especially blood thinners.
8. Toxicology & Storage
Overdose: Intraocular overdose (>0.05 mL) may cause acute increase in intraocular pressure leading to pain, nausea, vomiting, and potential retinal artery occlusion. Systemic overdose is improbable due to route of administration.
Storage: Store in a refrigerator at 2°C to 8°C. DO NOT FREEZE. Keep the vial/syringe in the outer carton to protect from light. The product should be used immediately after opening. Do not use if the solution is discolored or contains particles. Do not shake. For single use in one eye only. Discard any unused portion.