Which of the following drug is deposited in the retina ?
First, I remember that certain drugs are known to accumulate in the retina. Chloroquine comes to mind. It's an antimalarial drug, and I recall that it can cause retinopathy. The mechanism involves the drug accumulating in the retinal pigment epithelium, leading to damage over time. Another possibility might be hydroxychloroquine, which is similar but perhaps less toxic. Then there's ethambutol, which affects the optic nerve, but not the retina specifically. Digoxin is a cardiac drug, and while it can have ocular side effects, I don't think it's deposited in the retina. Amiodarone is another cardiac drug that can cause corneal microdeposits, but again, not the retina.
Wait, the question is about the retina. Chloroquine and hydroxychloroquine are definitely the main ones here. The key difference is that hydroxychloroquine is less likely to cause retinopathy but still can. The problem is that without the options, I have to assume which one is the correct answer. Let's say the options include chloroquine, hydroxychloroquine, ethambutol, and amiodarone. Then the correct answer would be chloroquine. But if hydroxychloroquine is an option, it's also possible. But since the question is about deposition, chloroquine is more notorious for this.
So, the core concept here is the deposition of antimalarials in the retina. Chloroquine accumulates in the retinal pigment epithelium, leading to toxicity. The mechanism involves the drug's basic nature, which binds to phospholipids in the cell membranes, causing structural damage. The other drugs either affect different parts of the eye or aren't deposited there. The clinical pearl is to monitor patients on long-term chloroquine therapy with regular ophthalmologic exams to detect retinopathy early. The correct answer is chloroquine.
**Core Concept**
The question assesses knowledge of drugs known to accumulate in the retina, particularly **antimalarials** like **chloroquine** and **hydroxychloroquine**, which bind to retinal phospholipids and cause toxic damage. This is a classic example of **drug-induced retinopathy** due to **lysosomal accumulation** in retinal pigment epithelium.
**Why the Correct Answer is Right**
**Chloroquine** is a **basic antimalarial drug** that accumulates in the **retinal pigment epithelium (RPE)** and **macula**. Its quinoline ring binds to **lysosomal membranes** and **phospholipids**, causing structural damage and apoptosis. Chronic use leads to **bull's eye maculopathy**, with irreversible vision loss. Monitoring via **optical coherence tomography (OCT)** or **visual field testing** is critical for early detection.
**Why Each Wrong Option is Incorrect**
**Option A:** *Hydroxychloroquine* has a similar mechanism but is **less toxic** than chloroquine, with a higher therapeutic index.
**Option