Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (792 page)

CARDIOVASCULAR DRUGS (SEE DIGOXIN)
*

   Definition

   Cardiovascular drugs include the antiarrhythmics, the anticoagulant warfarin, and antihypertensives, as well as the β-adrenergic antagonist propranolol and the drug digoxin (see p. 925).

   
Normal therapeutic values:
see Table 16.15.

TABLE 16–15. Cardiovascular Drugs

*Toxic concentrations have not been established.
† Monitor TSH and T
₄
values during therapy.
‡ Prothrombin time is used to assess efficacy as target INR: 2.0–3.0. Consider long-term, low-intensity (INR 1.5–2.0),
or standard-intensity (INR 2–3) warfarin therapy for patients with idiopathic events.
§ Effect on platelets may increase bleeding time.
¶ Decreased glucose tolerance.

   Use

   To treat arrhythmia, hypertension, blood clotting, and angina.

   The majority of these drugs are not routinely monitored as clinical effects do not generally correlate with serum or plasma levels. Notable exceptions are digoxin and procainamide.

   Where concentrations are required, specific gas chromatography and HPLC procedures have been developed (e.g., procainamide/
N
-acetylprocainamide [NAPA], quinidine, mexiletine, diltiazem, verapamil, amiodarone, and metabolite, warfarin). Limits of quantitation vary according to the drug and methodology.

   Immunoassay tests (e.g., FPIA) are available for procainamide, quinidine.

   In addition, lidocaine, diltiazem, verapamil, and quinidine are qualitatively detectable in urine with a simple alkaline liquid–liquid or solid-phase extraction followed by GC/MS analysis. Limits of detection range from 50 to 250 ng/mL.

   Interpretation

   Rifampin may decrease verapamil serum concentrations.

   Limitations