The calculation of the maximum number of milligrams a child Andy's size should receive should read:

As students work through the math, they see that the dose of acetaminophen the aunt gave Andy is much higher than the recommended maximum dose. Students can hypothesize, based on their understanding of dose and concentration and its relationship to size, that Andy was sick from too much acetaminophen.

Content Standard A: Use mathematics in all aspects of scientific inquiry.

Content Standard E: Students should develop understandings about science and technology. Technological solutions have intended benefits and unintended consequences. Some consequences can be predicted, others cannot.

3. Distribute copies of the second page of Master 4.3, A Poisonous Dose? The Problem. Instruct students to continue to work in their teams of three to complete Part II up to the conclusion. Then ask students to work individually on the conclusion by writing about how they think the accidental overdose of acetaminophen happened.

The calculation of the amount of acetaminophen in four doses of Children's Suspension Liquid should read:

Andy's mother uses a teaspoon to measure a dose of Children's Suspension liquid. Andy's aunt used a teaspoon to measure Infants' Concentrated Suspension Drops. The dosage chart says to use a dropper to measure infants' drops.

Students can conclude that incorrect amounts of acetaminophen were given to Andy because his aunt did not understand that the acetaminophen in infants' formula is concentrated: It cannot be measured using the same units (teaspoons) as the children's formula. In fact, a teaspoon of infants' formula is more than three times stronger than a teaspoon of children's formula. Instead of teaspoons, infants' formula should be measured in droppers, which is indicated on the dosage chart. Unfortunately, the similarity in the appearance of the two liquids leads parents, care givers, and even doctors to believe that the two medicines are interchangeable.

Collect students' written conclusions of what happened to Andy. Assess students' writing for understanding of the roles dose and concentration played in Andy's overdose and how the confusion over the two kinds of acetaminophen led to the problem.

Students may ask why the infants' formula is stronger, when medicine formulas usually get stronger for people only as their body size gets bigger. Because it is so difficult to give medicine to a baby, it is important to pack as much acetaminophen as possible into the smallest volume of liquid. The higher concentration of the acetaminophen in infants' formula ensures that parents can administer the appropriate amount of medicine with the least amount of trouble.

4. Display the second page of the transparency you made from Master 4.2, A Poisonous Dose? The Case History. Review with students the diagnosis and treatment.

The doctor handling Andy's case had seen severe liver damage and even death from liver failure among children who experienced accidental acetaminophen poisoning. She knew that an overdose of acetaminophen is 150 milligrams for each kilogram of body weight. For Andy, who weighs 12 kilograms, an overdose would be 1,800 milligrams. In Part I, students calculated that Andy received 2,000 milligrams of acetaminophen, clearly an overdose. The doctor administered an antidote (n-acetylcysteine) within 8 to 12 hours of the poisoning and the boy recovered.

5. Ask students how they think a mistake like the one that poisoned Andy could be avoided.

Because of situations like Andy's, changes in the labels and inserted instructions for acetaminophen products now inform people of the potential dangers of taking too much acetaminophen and more clearly describe appropriate dosage. Adults are reminded to use the dropper for the infants' formula acetaminophen, which is the appropriate unit of measure.

Weight (lbs)	Age	Infants' Concentrated Drops 80 mg/0.8 ml (dropperful)	Children's Suspension Liquid and Elixir 160 mg/5 ml (teaspoon)	Children's Soft Chews Chewable Tablets 80 mg each	Junior Strength Chewable Tablets/Caplets 160 mg each
6–11	0–3 months	½ = (0.4 ml)
12–17	4–11 months	1 = (0.8 ml)	½ (tsp)
18–23	12–23 months	1½ = (0.8 + 0.4 ml)	¾ (tsp)
24–35	2–3 years	2 = (0.8 + 0.8 ml)	1 (tsp)	2
36–47	4–5 years		1½ (tsp)	3
48–59	6–8 years		2 (tsp)	4	2
60–71	9–10 years		2½ (tsp)	5	2½
72–95	11 years		3 (tsp)	6	3
96 and over	12 years				4

ACTIVITY 3: THE CHEMICAL CAFFEINE: HOW DO YOU RESPOND?

Note: Before beginning this investigation, be sure to have a signed permission letter from parents or guardians for the students to ingest a caffeinated soft drink (use Master 4.4, Parent Letter). Those students for whom you do not have permission can participate in the investigation by drinking water; they will provide a control for the activity.

1. Because students' heart rates might be elevated from their walk to class, spend several minutes allowing students to rest and talk quietly. Find out what students know about the chemical caffeine. Use material from the Background Information to discuss caffeine briefly. Then, if you have not already done so, teach students how to find their pulse, count their heartbeats, and calculate their resting heart rate.

You can find your pulse most easily by pressing two fingers against the artery in your neck or on the inside of your wrist. It is easiest to count beats for only 15 seconds and then multiply the number you count by four to find your resting heart rate for one minute. Repeat the counting several times until most students have calculated a resting heart rate that is close to the same number several times in a row. Alternatively, you can have partners verify each other's heart rate.

2. Distribute Master 4.5, The Chemical Caffeine: How Do You Respond?, one to each student. On your signal, ask students to measure their heartbeats one more time for 15 seconds, stopping when you call time. Instruct students to calculate their resting heart rate for one minute by multiplying the number they counted by four. Direct them to record it on the data table on the master.

3. Ask students to work in pairs. Distribute the cans of the same kind of caffeinated soft drink, one to each student. Instruct students to follow the directions on the master. Remind them to continue to sit at rest. They can talk to their partner but should keep their bodies still so that they do not elevate their heart rate with activity.

Content Standard A: Students should develop abilities necessary to do scientific inquiry and understandings about scientific inquiry.

Tip from the field test: Assign some reading to students from which they can take a break periodically to measure their heart rate. Planning ahead for quiet activity helps keep the students focused on the task.

4. When all the students have filled in their data tables and calculated the difference between their resting heart rate and the highest heart rate after ingesting a caffeinated soft drink, discuss their findings by asking questions such as these:

• Did your heart rate go up, down, or stay the same after you drank a caffeinated soft drink?
  
  
  On average, most students should have seen their heart rate go up after drinking the caffeinated soft drink. Some sample data from a field-test class looked like this:

Measurements of Heart Rate at Rest and After Caffeine

Male or Female	Resting Heart Rate	Highest Post-Caffeine Heart Rate
F	80	88
M	88	100
M	76	116
M	68	76
M	72	92
M	80	92
F	76	92
F	68	84
F	68	92
F	72	80
M	80	74
M	64	84
F	68	88
F	84	84
M	80	96
M	72	104

• On the basis of your observations, what generalization can you make about the effect of caffeine on the human body?
  
  Caffeine appears to increase heart rate.
  
  
• Why was it important that all students drank the same kind and amount of soft drink?
  
  Students will recognize that the variable they are interested in testing is individual susceptibility to caffeine. They need to keep as many other factors in the investigation constant, such as amount and kind of soft drink (because different soft drinks have different amounts of caffeine), time of day for the investigation, and temperature of the classroom.
  
  
• Did all the members of the class have exactly the same results when they drank a caffeinated soft drink?
  
  While most members of the class will see their heart rate increase, the amount of increase will vary significantly.
  
  
• Compare your results with those of other members of the class. What is your individual susceptibility to caffeine?
  
  Ask students to compare how much their heart rates increased after exposure to caffeine. Those whose heart rates increased significantly can draw the conclusion that they are very susceptible to caffeine. Those whose heart rates did not increase very much, or went down, can draw the conclusion that they are less susceptible to caffeine.
  
  
• Why might some people be more individually susceptible to the effects of caffeine than others?
  
  Students vary from one another in gender, size, frequency of caffeine consumption, metabolic rates, and so on. This variability makes each student react differently to exposure to caffeine.
  
  
• What do the results of your investigation tell you about the possible risks to some people of ingesting the chemical caffeine?
  
  Although research has shown that caffeine is safe to consume in moderate amounts, doctors suggest that people who have high blood pressure or trouble with irregular heartbeats avoid caffeine.

Extension Activity

Ask students to examine the labels from some product packages for directions for use and warnings. Suggest that students look at a variety of products, such as household cleaners, cold medicines, and vitamins. Instruct students to summarize information about the following for each product:

• route of exposure
• dose
• individual susceptibility

Students' summaries will vary depending on the products they choose. Encourage them to examine at least one product that is meant for human ingestion, such as a medication, because the product label should contain information about dose and individual susceptibility. Remind them that labels from some products, such as household cleaners, will have information about routes of exposure but probably will not include information about dose or individual susceptibility.

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