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CHAPTER OBJECTIVES

  • Define active pharmaceutical ingredient1 (API) and drug product (finished dosage form).

  • Define pharmaceutical equivalence (PE) and therapeutic equivalence (TE).

  • Describe the physical and biopharmaceutical properties of API that are important in the design and performance of drug products.

  • Describe the main methods used to test PE of the API or the dosage form (drug product).

  • Explain the relationship of PE, bioequivalence (BE), and TE.

  • Explain whether a generic drug product that is not an exact PE can be TE.

  • Explain why a generic drug product with identical PE may not lead to equivalent pharmacokinetic and pharmacodynamic performance.

  • Define complex drug products and explain the problems for establishing pharmaceutical equivalence for these products.

INTRODUCTION

In order to bring a new drug to the United States market, a company must submit a new drug application (NDA) to the FDA for review and approval. Regulatory approval is based on evidence that establishes the safety and efficacy of the new drug product through one or more clinical trials (FDA, cited June 5, 2014). The development of a new drug, from discovery to entering the market, is a lengthy and expensive process. These clinical studies are typically performed by a large pharmaceutical company known as the innovator company. The innovator company patents the new drug and gives it a brand name. The brand drug product is available from only one manufacturer until patent expiration. These drug products are also known as single-source drugs, which are marketed at a high price, a practice that allows the company to recover the costs in development and to make a profit. Patents are critical for encouraging innovation that is needed for developing new drugs to effectively treat diseases. Once the patent expires, other companies can manufacture and market generic versions of the brand drug product after gaining approval for marketing by a regulatory agency through an Abbreviated New Drug Application (ANDA) process, which presents a substantially lower barrier than the NDA process (Fig. 26-1). At that point, the drug becomes a multisource drug, provided the generic drug products contain the same active pharmaceutical ingredient (API) in the same dosage form and given by the same route of administration (Chapters 8 and 29). Through market competition, the price of a multisource drug is lower than the single-source brand drug (Cook, et al 1998). This makes the drug more affordable to the general public. The competition of generic drug products reduces global healthcare costs and motivates brand name companies to sustain their business through more innovations. Generic drug products are especially important for countries where innovator drug products are not available. Therefore, a balance must be reached to both encourage innovation by brand name companies and curb costs in drug purchasing through generic drug competition.

FIGURE 26-1

Illustration of the different barriers that must be overcome to gain the approval of a new drug product through ...

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