Cystoid macular edema is a known side effect of different systemic and local medications. Nicotinic acid used as a hypolipemiant agent can cause cystoid macular edema. Local adrenergic antiglaucomatous drugs as well as prostaglandin analogs can induce cystoid macular edema especially if other risk factors, which will be discussed, are present. Benzalkonium chloride, a universal conservative agent, can also favour cystoid macular edema.