Therapeutic Drug Monitoring of Antiasthmatic Drugs

Theophylline is a bronchodilator and respiratory stimulant effective in the treatment of acute and chronic asthma. The drug is readily absorbed after oral absorption, but peak concentration may be observed much later with sustained release tablets. The bronchodilator effect of theophylline is proportional to the log of serum drug concentration over a range of 5-20 ^g/mL (129). Adverse reactions may be observed

Table 6

Therapeutic Drug Monitoring of Cardioactive Drugs

Table 6

Therapeutic Drug Monitoring of Cardioactive Drugs

Drug

Specimen Requirement

Therapeutic Rangeb Trough

Costa

Amiodarone

Serum or plasma

1.0-2.5 pg/mL

$$$

Digoxin

Serum or plasma

0.8-2.0 ng/mL

$

Disopyramide

Serum or plasma

1.5-5.0 pg/mL

$$$

Flecainide

Serum or plasma

0.2-1.0 pg/mL

$$

Lidocaine

Serum or plasma

1.5-5.0 pg/mL

$$

Mexiletine

Serum or plasma

0.5-2.0 pg/mL

$$$

Propanolol

Plasma

50-100 ng/mL

$$

Procainamide

Serum or plasma

4-10 pg/mL

$$ (both tests)

and NAPA

4-8 pg/mL

Quinidine

Serum or plasma

2-5 pg/mL

$

Tocainide

Serum or plasma

5-12 pg/mL

$$$

Verapamil

Serum or plasma

50-200 ng/mL

$$$

$, < $75; $$, < $100; $$$, > $100; $$$$, > $150. a The costs are based on published charge for these tests in our hospital laboratory and reference laboratories.

b Therapeutic ranges are suggested ranges based on ranges used in our hospital laboratory as well as published ranges in textbooks and test catalogues of reference laboratories. Reference ranges may vary significantly depending on patient population, disease states, and others.

$, < $75; $$, < $100; $$$, > $100; $$$$, > $150. a The costs are based on published charge for these tests in our hospital laboratory and reference laboratories.

b Therapeutic ranges are suggested ranges based on ranges used in our hospital laboratory as well as published ranges in textbooks and test catalogues of reference laboratories. Reference ranges may vary significantly depending on patient population, disease states, and others.

at concentrations exceeding 20 ^g/mL. However, serum therapeutic concentrations between 10 and 20 ^g/mL have also been reported (130). Theophylline is metabolized by hepatic cytochrome P450, and altered pharmacokinetics of theophylline in disease states have been reported. Clearance of theophylline is slow in neonates compared with that in adults, while theophylline metabolism is also altered in hepatic disease. Acute viral illness associated with fever may prolong the half-life of theophylline (131). Patients with pneumonia and episodes of severe airways obstruction also may metabolize theophylline slowly (132). Altered pharmacokinetics of theophylline in pregnancy and among smokers have been discussed earlier in this chapter. Treating debilitated elderly patients with a nasogastric tube may significantly alter the pharmacokinetics of theophylline. Berkovitch et al. reported that when similar doses of theophylline were administered through nasogastric tubes and orally, patients receiving theophylline through nasogastric tubes demonstrated unexpectedly low serum theophylline concentrations. For example, mean trough theophylline concentration was 3.78 ^g/mL in patients receiving theophylline through nasogastric tubes compared with a mean theophylline plasma concentration of 8.63 ^g/mL when patients received theophylline orally. Peak plasma concentration of theophylline also differed significantly between these two groups (133). Reference ranges and costs of monitoring of antiasthmatic drugs are given in Table 7.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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