Question

11.7 Please read the background information on theophylline prior to answering this questions on Page 253. A.M. is an 80?kg, 5 foot 11 inch, 50?year?old male who is to be treated with theophylline for an asthmatic attack. Theophylline’s clearance in A.M. is estimated to be 1.6 L/h based upon his demographic features: severe obstructive pulmonary disease, congestive heart failure and smoking a pack of cigarettes a day. The population average volume of distribution of theophylline is 0.5 L/kg. (a) Advise on a suitable infusion rate of aminophylline (S = 0.8) to achieve a plasma concentration of 15 mg/L theophylline? Answer: ___________________________________ (1 Point) (b) Determine a suitable intravenous loading dose of aminophylline. Answer: __________________________ (1 Point) (c) What is the earliest time that a plasma sample can be taken to determine if the steady?state plasma concentration is in the therapeutic range. Answer: ___________________________ (1 point) (d) An infusion of 30.75 mg/h is used. A steady?state plasma sample is obtained and reveals a theophylline Cp value of 25 mg/L (A.M’s clearance was only estimated initially based upon patient demographics). Recommend a more suitable infusion rate based upon this information to achieve a steady state concentration of 15 mg/L. Answer: _____________________________ (2 Points) (e) Assume a new infusion rate is used and that steady state is achieved. The infusion is terminated. How long would it take plasma concentrations to fall to 3.5 mg/L. (1 Point)

Answer 1

Ans a:

If the patient is having more than 60 years we can advise 0.3mg/kg/hour and below 60 years 0.4mg/kg/hour upto 900mg per day.

Ans b:

The suitable dose of aminophylline is 160mg/hour .

Ans c:

The earliest time the steady state plasma concentration is in the theraputthe range one half life = 50%,2 half life= 75%, so it is the time to reach the steady state plasma concentration in therapeutic range.

Rate of drug input= rate of drug output.

dcp/dt = 0.

Ans e:

The time taken for plasma voconcentrati to fall to 3.5mg/L from 15mg/L is two days.