Which of the following is an example of OTC insulin?

Over-the-counter (OTC) insulin typically refers to insulin formulations that do not require a prescription for purchase. In the context of available insulin products, regular (R) insulin and NPH (Neutral Protamine Hagedorn) insulin have historically been available for purchase without a prescription. The combination of NPH and regular insulin, often found in the 70/30 formulation, falls into this category.

NPH is an intermediate-acting insulin, while regular insulin is a fast-acting insulin. When combined, they provide a balanced control of blood glucose levels for individuals managing diabetes. This combination is often favored for convenience and ease of use in patients who may not require intensive diabetes management or who face barriers to acquiring prescription medications.

Other options, such as Lantus (glargine), Humalog (lispro), and Novolog (aspart), are considered prescription-only medications due to their more specialized use, monitoring requirements, or the complexity of their action profiles. Therefore, the option representing the 70/30 combination of NPH and regular insulin is recognized as the correct answer as it reflects an accessible form of insulin for patients without the need for a prescription.