Dose Adjust Problems

Theophylline:

Problem 01. You need to initiate a theophylline regimen via IV infusion in a 25 year old female who weighs 50 kg.

1. What loading dose would be required to produce an initial concentration of 10 mg/L?

Problem 02. A female patient to be given theophylline weighs 50 kg.

1. What is the predicted clearance rate in this patient?

Problem 03. Assume that you want to produce a 10 mg/L steady state concentration of theophylline in a 50 kg female.

1. What is the initial infusion rate in mg/h?

Problem 04. A patient has been receiving a theophylline infusion of 25 mg/h. The measured concentration at steady state was 23 mg/L.

1. What is the highest recommended concentration of theophyline?
2. What new dose of theophylline should be recommended?

Problem 05. Theophylline is supplied as hydrous aminophylline for infusion. Each mg of hydrous aminophylline contains 0.79 mg theophylline. The "core" drug molecule devoid of the salt or ester moiety is often called the drug base.

1. How much hydrous aminophylline should be infused per hour to produce an infusion rate of 20 mg/h of theophylline?

Problem 06. Theophylline is supplied in several forms for oral administration. One form is as enteric coated aminophylline tablets (0.79 mg theophylline/mg aminophylline) in sizes of 100 and 200 mg. An estimated dose rate of 25 mg /h is needed in a 50 kg patient. Oral F is approximately 1.

1. What is the estimated dose rate of aminophylline?
2. What is the estimated dose per 12 h?
3. What is a reasonable combination of tablets to produce this dose?
4. If CL in this patient is 1.95 L/h, what Css do you expect from this combination of tablets?

Problem 07. One speaks of a steady state concentration for an infusion of drug. When drug is given by oral administration, one must think of average concentration with oscillation. The average concentration (Css(ave))corresponds to the Css and can be computed from the following formula.

1. What is the average concentration of theophylline if one administers 316 mg of theophylline at a dose interval of 12h to a 50 kg patient? CL = 1.95 L/ 50 kg.

Problem 08. One should be concerned about the degree of oscillation of plasma drug concentrations when giving a drug by intermittent dosage. Given the following pieces of information: 316 mg theophylline per 12 h. Patient weight = 50 kg. CL = 1.95 L / 50 kg. Vd = 0.5 L/kg.

1. Is this enough information to calculate the oscillation?
2. What more does one need?

Problem 09. Given a dose interval of 12 hours and a Ke of 0.077/h. Also, a dose of 316 mg theophylline per 12 hours and a body weight of 50 kg and a Vd of 0.5 L/kg.

1. What is the oscillation factor?
2. What is the absolute degree of oscillation?
3. On what crucial assumption is this estimate of peak and trough based?
4. How will the peaks and troughs of drug given PO compare to those computed by the formulae used in this course?