Question

Which of the following drugs is NOT used for the medical treatment of diabetic retinopathy?

• A. Tamoxifen
• B. Benfotiamine
• C. Pyridazinones
• D. Ruboxistaurin

Hint:

One of these is a breast-cancer anti-oestrogen, not a retinal protectant.

Answer 1

The Correct Option is A

Frame the question around mechanism. Drugs proposed for diabetic retinopathy interrupt the chemical chain set off by chronic high glucose, so look for agents that act on glycation, the protein kinase C pathway, or microvascular oxidative injury, and find the one that does none of these.

Benfotiamine is a fat-soluble form of vitamin B1 that diverts excess glucose metabolites away from the harmful pathways and lowers tissue advanced glycation products, so it fits. Ruboxistaurin is designed specifically to inhibit the beta isoform of protein kinase C, a key driver of retinal vascular leakage, so it also fits. Pyridazinones are vasoactive compounds explored for improving retinal blood flow, so they belong as well.

That leaves tamoxifen. It is an anti-oestrogen for breast cancer with no place in retinopathy therapy, and ironically high or prolonged doses can deposit refractile crystals in the retina and harm vision.

So the agent with no therapeutic role here is tamoxifen.
\[\boxed{\text{Tamoxifen}}\]