A nurse is preparing to administer acetaminophen 320 mg PO every 4 hr PRN for pain.

The amount available is acetaminophen liquid 160 mg/5 mL. How many mL should the nurse administer per dose? Round the answer to the nearest tenth and use a leading zero if it applies.

Do not use a trailing zero.

Choice A rationale

Vision changes resulting from retinal tissue pulling away from the underlying choroid describe a retinal detachment. This is a medical emergency characterized by sudden flashes of light, floaters, or a curtain-like shadow over the visual field. Open-angle glaucoma is a chronic, progressive condition rather than an acute mechanical separation of the retina. The pathology of glaucoma involves the optic nerve head rather than the total detachment of the neurosensory retinal layers from blood supply.

Choice B rationale

A cloudy lens that alters the passage of light describes a cataract. Cataracts lead to a gradual, painless blurring of vision and increased glare sensitivity as the proteins in the lens clump together. While both cataracts and glaucoma are common in aging populations, they have different mechanisms. Glaucoma specifically involves the drainage of aqueous humor and the resulting pressure on the optic nerve, whereas cataracts are strictly an opacity issue within the crystalline lens structure.

Choice C rationale

Open-angle glaucoma is characterized by a slow, progressive increase in intraocular pressure, typically ranging above the normal 10 to 21 mmHg. This pressure occurs because the aqueous humor cannot drain efficiently through the trabecular meshwork. Over time, the elevated pressure damages the optic nerve fibers, leading to a gradual loss of peripheral vision, often called tunnel vision. Because this happens slowly and painlessly, many patients remain asymptomatic until significant permanent visual loss occurs.

Choice D rationale

Blood vessels leaking fluid or blood under the retina is characteristic of wet macular degeneration. This condition involves neovascularization, where fragile new blood vessels grow and leak, causing rapid and severe central vision loss. In contrast, open-angle glaucoma affects the peripheral vision first and is related to fluid pressure within the anterior chamber of the eye rather than subretinal hemorrhaging or exudative processes in the macula. Glaucoma management focuses on lowering intraocular pressure.

Step 1 is 500 mg ÷ 125 mg = 4.

Step 2 is 4 × 5 mL = 20. The final calculated answer is 20 mL.