Imagine you are a physician in a hospital emergency room. A frantic parent has j

Question

Imagine you are a physician in a hospital emergency room. A frantic parent has just brought in a child. Ninety minutes earlier, the child ingested eleven 100-mg theophylline tablets (medication taken for asthma). Like most oral drugs, theophylline is absorbed into the bloodstream at a rate proportional to the amount present in the gastrointestinal tract. The drug is eliminated from the bloodstream at a rate proportional to the amount present in the bloodstream. You check the Physician’s Desk Reference (PDR) and find that the brand of theophylline swallowed by the child has an absorption half-life of 5 hours and an elimination half-life of 6 hours. The PDR warns that a blood-level concentration of 100 mg/L or more is seriously toxic and a concentration of 200 mg/L or more is fatal. Based on body mass, you estimate that the child has 2.0 L of blood. You also determine that, because of the 2 hour delay, the pills have already passed from the child’s stomach to his intestines, so that it is too late to eliminate the drug from the child’s body by inducing vomiting. Your task is to determine if the child is in danger, and if so, what action to take in order to save his life.

4.) Determine the largest amount of theophylline the child ever has in his bloodstream, and the time at which this maximum level occurs. How much theophylline remains in his gastrointestinal tract at this time?

5.) Determine the largest amount of theophylline the child ever has in his bloodstream, and the time at which this maximum level occurs. How much theophylline remains in his gastrointestinal tract at this time?

6.) Since it is too late to change the rate of absorption from the gastrointestinal tract, you must therapeutically change the elimination rate (eg: add charcosl to the bloodstream extracorporeally). Find the smallest value for the constand k2 that ensures that the concentration of theophylline in the child's bloodstream remains below the lethal level.

Explanation / Answer

1. The overdosing of the theophylline can be treated by using charcoal as it efficiently absorbs the drug. In case or oral drug administered, the elimination is 1.25 faster than normal. But in case of potentially fatal overdosing and the case like this that vomiting is not an option, a dialysis-like procedure is used whereby the bloodstream is made to pass over a bed of charcoal. However the process is risky, but rate of elimination is six times faster than the normal rate of elimination.

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