After teaching a client who is prescribed a long-acting beta agonist medication, a nurse assesses the client's understanding.
Which statement indicates that the client comprehends the teaching?

Step 1: Convert pounds to kilograms. 55 lb ÷ (2.2 lb/1 kg) = 25 kg.

Step 2: Calculate the total milligrams per 24 hours. 7 mg/kg/24 h × 25 kg = 175 mg/24 h.

Step 3: Calculate the milligrams per dose (q h implies 2 doses per 24 hours). 175 mg/24 h ÷ 2 doses = 87.5 mg/dose.

Step 4: Calculate the volume in milliliters per dose. 87.5 mg ÷ (125 mg/5 mL) = 3.5 mL. 3.5 mL will be administered for each dose.

Choice A rationale

There is no specific scientific rationale requiring extra vitamin C supplementation while on isoniazid. Isoniazid can cause pyridoxine (vitamin B6) deficiency, which leads to peripheral neuropathy, due to its chemical structure interfering with pyridoxal phosphate metabolism. Therefore, vitamin B6 supplementation is routinely prescribed to prevent this adverse effect, rather than vitamin C, which is not directly involved in this metabolic pathway.

Choice B rationale

Taking isoniazid with milk or juice is generally discouraged as it can interfere with drug absorption. Isoniazid absorption is optimized in an acidic environment and can be reduced by food, particularly dairy products, which can chelate the drug or alter gastric pH. Therefore, consuming it with milk or juice might decrease its bioavailability, leading to sub-therapeutic drug levels and potentially compromising treatment efficacy against Mycobacterium tuberculosis.

Choice C rationale

Isoniazid absorption is best on an empty stomach because food, especially high-fat meals, can significantly decrease its bioavailability. The presence of food in the stomach can delay gastric emptying and interfere with the dissolution and absorption of the drug from the gastrointestinal tract. Optimal absorption ensures that therapeutic drug concentrations are achieved in the bloodstream, which is crucial for effectively inhibiting bacterial cell wall synthesis in Mycobacterium tuberculosis.

Choice D rationale

Isoniazid is not known to cause permanent staining of contact lenses. This side effect is associated with rifampin, another antituberculosis drug, which can cause reddish-orange discoloration of body fluids, including tears, urine, and sweat, due to its chromophore properties and excretion pathways. Isoniazid's mechanism of action and metabolic breakdown do not produce colored metabolites that would result in such staining.