A patient with no known allergies is to receive penicillin every 6 hours. When administering the medication, the nurse observes a fine rash on the patient's skin. The most appropriate nursing action would be to:

Correct Answer: A

Rationale: In this scenario, the appearance of a rash after administering penicillin, even in a patient with no known allergies, is concerning for a potential allergic reaction. The appropriate action for the nurse to take is to withhold the medication and notify the physician. This precaution is necessary to prevent further administration of a medication that may be causing an adverse reaction, as allergic reactions can range from mild to severe and require immediate intervention.

Correct Answer: D

Rationale: The correct answer is D because the vastus lateralis muscle is located in the anterior thigh, and the described method ensures proper localization for a safe intramuscular (I.M.) injection. The vastus lateralis is part of the quadriceps muscle group and is a common site for I.M. injections, particularly in infants and adults when other sites are contraindicated. To locate it, the clinician divides the thigh between the greater trochanter (the bony prominence at the top of the femur) and the lateral femoral condyle (the bony protrusion on the outer side of the knee) into thirds. The middle third on the anterior aspect of the thigh is the correct injection site, as it avoids major nerves and blood vessels while ensuring the medication is delivered into the muscle mass. This method is widely accepted in clinical practice and supported by anatomical studies. Choice A is incorrect because it describes the dorsogluteal site (upper outer quadrant of the buttock), which is not the vastus lateralis. The dorsogluteal site is associated with the gluteus maximus muscle and carries a higher risk of injuring the sciatic nerve or superior gluteal artery if not properly located. While it is a valid I.M. injection site, it is not the correct answer for targeting the vastus lateralis. Choice B is incorrect because it refers to the deltoid muscle site, located on the lateral aspect of the arm. The deltoid is another common I.M. injection site, particularly for vaccines, but it is not the vastus lateralis. The described landmark (acromion process) is specific to the deltoid and irrelevant to locating the vastus lateralis in the thigh. Choice C is incorrect because it describes an area on the abdomen (anterior to the umbilicus), which is not used for I.M. injections. The abdominal area is typically associated with subcutaneous injections (e.g., insulin) due to the presence of adipose tissue, not muscle mass. There is no valid anatomical basis for administering an I.M. injection in this location, making it entirely unrelated to the vastus lateralis. The correct method (D) ensures accurate placement in the vastus lateralis, minimizing complications such as nerve injury, injection into subcutaneous tissue, or accidental entry into blood vessels. The other choices either describe alternative injection sites or irrelevant anatomical locations, demonstrating a misunderstanding of the vastus lateralis's position and function. Proper identification of anatomical landmarks is critical for safe and effective I.M. injections, and the vastus lateralis is particularly advantageous due to its accessibility and reduced risk of complications compared to other sites.

Correct Answer: D

Rationale: The correct answer is **D: 25G, 5/8" long** because insulin injections are typically administered subcutaneously (into the fatty tissue beneath the skin), and this needle size is optimal for such delivery. A 25G needle is thin enough to minimize discomfort while still allowing the viscous insulin solution to pass through smoothly. The 5/8" length is appropriate for most patients, including those with average subcutaneous fat thickness, as it ensures the medication is deposited in the correct tissue layer without risking intramuscular injection, which could alter absorption rates. This combination balances patient comfort with clinical efficacy, making it the standard for insulin administration. **Why the other options are incorrect:** - **A: 18G, 1 ½" long** – An 18G needle is excessively large for insulin injections. Such a thick gauge would cause significant pain and tissue trauma, and the 1 ½" length is unnecessarily long for subcutaneous injections, increasing the risk of intramuscular administration, which is undesirable for insulin due to faster absorption rates. This size is more suited for procedures like blood donation or IV access, not routine insulin delivery. - **B: 22G, 1" long** – While a 22G needle is thinner than an 18G, it is still thicker than the ideal for insulin. A 1" length may be suitable for some patients with thicker subcutaneous tissue, but it is unnecessarily long for most, increasing the risk of intramuscular injection. A shorter, finer needle (like 25G, 5/8") is preferred for routine use to ensure comfort and proper placement. - **C: 22G, 1 ½" long** – This option combines the drawbacks of both excessive gauge and excessive length. A 22G needle is too thick for comfortable insulin injections, and the 1 ½" length is far too long, almost guaranteeing intramuscular injection in many patients. Such a combination would lead to poor patient compliance due to pain and unpredictable insulin absorption kinetics. The key considerations for insulin needle selection are minimizing discomfort (favoring smaller gauges like 25G–31G) and ensuring subcutaneous deposition (favoring shorter lengths like 5/8" or 4mm for most patients). Option D aligns perfectly with these principles, whereas the other choices either compromise comfort, accuracy, or both.

Correct Answer: D

Rationale: The correct answer is **D: 26G** because intradermal injections require a fine, short needle to deposit medication or vaccines just below the epidermis without penetrating deeper tissues. A 26G needle is typically 26-gauge with a short bevel (usually ⅜ to ½ inch in length), which allows precise delivery into the dermal layer while minimizing trauma and leakage. The thin diameter reduces discomfort for the patient and ensures proper absorption, as intradermal injections rely on slow diffusion from the dermis into the local capillaries. This gauge is standard for procedures like tuberculin (TB) skin tests or allergy testing, where accuracy in placement is critical. **A: 20G** is incorrect because it is far too large for intradermal injections. A 20-gauge needle is thick and long, typically used for procedures requiring rapid fluid delivery (e.g., IV infusions or blood draws). Using such a large needle for intradermal injection would cause unnecessary pain, increase the risk of bleeding, and likely deposit the medication too deeply into subcutaneous or muscular tissue, compromising the intended immune response or diagnostic accuracy. **B: 22G** is incorrect because, while smaller than 20G, it is still too large for intradermal administration. A 22-gauge needle is commonly used for IM (intramuscular) injections or subcutaneous injections in adults, where deeper tissue penetration is needed. The diameter is too wide to reliably stay within the thin dermal layer, increasing the chance of misplaced medication and patient discomfort. **C: 25G** is incorrect because, although it is closer to the correct size, it is still less ideal than 26G for most intradermal procedures. While a 25-gauge needle can be used in some cases, it may not provide the same precision as a 26G needle, particularly for delicate applications like allergy testing where slight variations in depth can affect results. The marginally larger diameter may also cause more tissue disruption or leakage compared to the finer 26G needle. The choice of needle gauge balances precision, patient comfort, and clinical efficacy, and 26G is the optimal selection for intradermal injections due to its fine diameter and shallow penetration capability.

Correct Answer: A

Rationale: Parenteral administration refers to delivering medications via routes other than the digestive tract, typically involving injections. Penicillin, a widely used antibiotic, can be administered through specific parenteral routes to ensure optimal absorption, efficacy, and safety. The correct answer is **A (IM injection or an IV solution)** because penicillin formulations are specifically designed for intramuscular (IM) or intravenous (IV) administration. IM injections allow for slower absorption into the bloodstream, suitable for drugs like penicillin G benzathine, which provides prolonged action. IV administration delivers the drug directly into the bloodstream, ensuring rapid onset, which is critical in severe infections. Both methods are well-supported by pharmacokinetic studies and clinical practice guidelines. **Why other options are incorrect:** - **B (IV or intradermal injection):** Intradermal injections are used primarily for diagnostic tests (e.g., tuberculin skin tests) or vaccines, not for antibiotics like penicillin. The intradermal route lacks the capacity to deliver the volume or achieve the systemic drug levels required for antibiotic efficacy. - **C (Intradermal or subcutaneous injection):** Subcutaneous injections are unsuitable for penicillin because they can cause significant local irritation and inadequate absorption. Penicillin’s molecular properties and irritation potential make this route impractical, unlike drugs like insulin or heparin, which are designed for subcutaneous delivery. - **D (IM or subcutaneous injection):** While IM is correct, subcutaneous administration is inappropriate for penicillin due to the risk of tissue damage and inconsistent absorption. The subcutaneous layer lacks the vascularity needed for efficient drug distribution, leading to subtherapeutic levels and potential adverse reactions. The distinction between these routes hinges on the drug’s physicochemical properties, therapeutic goals, and anatomical considerations. Penicillin’s stability, solubility, and irritation profile limit its administration to IM or IV routes, ensuring both safety and clinical effectiveness. Misapplication via incorrect routes (e.g., intradermal or subcutaneous) could compromise treatment outcomes or cause harm, underscoring the importance of adhering to evidence-based administration practices.