How Drugs Work

Rationale and Objectives

A curriculum unit on the chemistry of OTC pain relievers is timely and relevant. It will provide students an opportunity to understand how OTC pain relievers work, what they contain, and the possible risks involved in their use. The unit will focus only on OTC pain relievers that contain acetaminophen, aspirin, ibuprofen and naproxen. It will not include topical pain relievers such as Bengay.

The curriculum unit will be implemented in my college–prep chemistry classes at Terra Nova High School located in Pacifica, CA. The majority of the students in chemistry are sophomores while the rest are juniors and seniors. They have all successfully completed one year of college prep Biology and Algebra 1. For some of the juniors and seniors, chemistry is their third science course (after Earth Science and CP Biology). A few are taking chemistry and physics simultaneously.

The unit will be part of my module on Rates of Chemical Reactions. It will serve as the real world application of our lesson on the role of catalysts in chemical reactions. The 2–week unit will be divided into three parts.

Part 1 will focus on the basic chemical concepts linked to painkillers. We will talk about the collision theory and the four factors that affect the rate of a chemical reaction which include temperature, concentration, surface area, and use of a catalyst. Specific objectives in this part include the following:

1. Relate reaction rates to collisions between reacting particles
2. Describe the role of activation energy in a chemical reaction
3. Identify factors that affect reaction rate
4. Explain the role of a catalyst

In part 2, we will discuss what happens inside our bodies when we experience a painful sensation. Specific objectives for this part are as follows:

1. Define pain and describe how a stimulus is interpreted by the brain as painful
2. Explain how pain is classified
3. Describe the molecular and structural features of prostaglandins
4. Describe how prostaglandins are formed in the body and the role played by arachidonic acid and cyclooxygenase
5. Identify the functions of prostaglandins

Part 3 will be on the chemistry of OTC NSAID (aspirin, ibuprofen and naproxen) and acetaminophen and how these substances work as pain relievers. Specific objectives are as follows:

1. Describe how each of the following was discovered: aspirin, acetaminophen, ibuprofen and naproxen
2. Explain how aspirin, ibuprofen and naproxen work to relieve fever, pain, inflammation and other symptoms
3. Explain why acetaminophen relieves pain and fever but not inflammation
4. Identify possible side effects of each of the following: aspirin, ibuprofen, naproxen and acetaminophen
5. Describe health threats associated with misuse/abuse/overdose of OTC pain relievers

The unit addresses California Chemistry Standards 8b, 8c and 8d on reaction rates. It also provides students and opportunity to acquire and enhance eight scientific and engineering practices that they should engage in throughout their K–12 education as identified in A Framework for K–12 Science Education: Practices, Crosscutting Concepts and Core ideas ⁵ . The framework is the basis of the Next Generation of Science Education Standards which is being drafted by a team of experts and will be released in fall 2012. The practices include

1. Asking Questions and Defining Problems
2. Developing and Using Models
3. Planning and Carrying out Investigations
4. Analyzing and Interpreting Data
5. Using Mathematics, Information and Computer Technology, and Computational Thinking
6. Constructing Explanations and Designing Solutions
7. Engaging in Argument from Evidence
8. Obtaining, evaluating, and communicating information