The physician orders 52 units of Humulin NPH insulin and 16 units of Humulin R insulin subcutaneously every morning.

The medication is supplied in 100 units/mL. How many units will the nurse administer? (Shade SYRINGE #3; LABEL CORRECTLY TO RECEIVE CREDIT)

Choice A rationale

Metabolism is primarily carried out by the liver, involving enzymatic biotransformation of drugs into more hydrophilic metabolites for excretion. While liver function can be impacted by systemic illness, renal failure's direct effect on drug metabolism is less significant than its impact on elimination. The liver's cytochrome P450 system typically remains functional.

Choice B rationale

Excretion is the primary elimination pathway for many drugs and their metabolites, mainly via the kidneys. In end-stage renal disease, glomerular filtration rate and tubular secretion are severely impaired, leading to accumulation of drugs and their toxic metabolites, necessitating dose adjustments or alternative elimination methods. Normal creatinine clearance is 80-120 mL/min.

Choice C rationale

Absorption refers to the movement of a drug from its administration site into the bloodstream. While renal failure can indirectly affect absorption through gastrointestinal changes (e.g., uremia-induced nausea), it is not the primary pharmacokinetic phase directly compromised by impaired kidney function. Bioavailability might be altered but not the fundamental absorption process.

Choice D rationale

Distribution involves the reversible movement of a drug from the systemic circulation into the interstitial and intracellular fluids. Renal failure can impact drug distribution due to fluid imbalances, altered protein binding (e.g., hypoalbuminemia), and changes in tissue perfusion, but it is not the most significant or direct pharmacokinetic impairment compared to excretion.

Choice A rationale

Administering only 0.5 mL subcutaneously is a common volume for certain medications, but it is not the maximum. Larger volumes can sometimes be administered, depending on the site and medication characteristics, without causing undue tissue distention or discomfort.

Choice B rationale

The subcutaneous tissue layer has a limited capacity for fluid absorption, and volumes exceeding 1 mL can cause tissue distention, discomfort, and potentially impair absorption due to increased pressure. This volume minimizes local tissue irritation and ensures optimal medication uptake into the systemic circulation.

Choice C rationale

Administering 2 mL subcutaneously is generally discouraged due to the potential for significant tissue distention, discomfort, and pain. Such a large volume can also lead to poor absorption and increased risk of local adverse reactions, making it an impractical and often unsafe choice for routine subcutaneous injections.

Choice D rationale

While 1.5 mL is closer to the maximum, it often pushes the limits of comfortable and effective subcutaneous administration. This volume may cause considerable discomfort, particularly in clients with limited subcutaneous tissue, and can compromise absorption rates.