Serum digoxin

Buspirone causes less additive CNS depression than do the other antianxiety drugs. However, it is recommended that concurrent use with a CNS depressant be avoided. Buspirone may increase serum digoxin levels, which increases the risk of digitalis toxicity. 

The effects of buspirone are decreased when the drug is administered with fluoxetine Increased serum levels of buspirone occur if the drug is taken with erythromycin or itraconazole Should any of these combinations be required, the dosage of buspirone is decreased to 2.5 mg BID, and the patient is monitored closely. Venlafaxine blood levels increase with a risk of toxicity when administered witii MAOIs or cimetidine There is an increased risk of toxicity when trazodone is administered with the phenothiazines and decreased effectiveness of trazodone when it is administered with carbamazepine Increased serum digoxin levels have occurred when digoxin is administered with trazodone There is a risk for increased phenytoin levels when phenytoin is administered witii trazodone... 

IV dosage depends on serum digoxin level or estimate of the amount of digoxin ingested average dose up to 800 mg (20 vials)... 

Which of Hie following serum digoxin levels would be most indicative that a patient taking digoxin may be experiencing toxicity ... 

Determine whether the patient is taking any drugs known to cause sinus bradycardia. If the patient is currently taking digoxin, determine the serum digoxin concentration and ascertain whether it is supratherapeutic (greater than 2 ng/mL [2.56 nmol/L]). 

Fig. 5 Variations in serum digoxin concentration in an elderly female patient during treatment with digoxin and metoclo-pramide or propantheline. (From Ref. 10.).

C. Hayes, V. Butler, and W. Gersony, Serum digoxin studies in infants and children, Pediatrics, 52, 561 (1973). 

In a subset of approximately 1800 patients enrolled in a trial (wherein dosing was based on an algorithm similar to that in the table below) the mean ( SD) serum digoxin oonoentrations at 1 month and 12 months were approximately 1.01 ng/mL and approximately 0.97 ng/mL, respeotively. 

Electrolyte disorders In patients with hypokalemia or hypomagnesemia, toxicity may occur despite serum digoxin concentrations less than 2 ng/mL, because potassium or magnesium depletion sensitizes the myocardium to digoxin. Therefore, it is desirable to maintain normal serum potassium and magnesium concentrations in patients being treated with digoxin. 

Fosinopril may cause a false low measurement of serum digoxin levels with the Digi-Tab RiA Kit for Digoxin other kits such as the Coat-A-Count RiA Kit, may be used. 

Amiodarone increases the hypoprothrombinemic response to warfarin (an oral anticoagulant) by reducing its metabolism. Patients receiving digoxin may undergo an increase in serum digoxin concentrations when amiodarone is added to the treatment regimen. Amiodarone interferes with hepatic and renal elimination of flecainide, phenytoin, and quinidine. 

Itraconazole has significant interactions with a number of commonly prescribed drugs, such as rifampin, phenytoin, and carbamazepine. Itraconazole raises serum digoxin and cyclosporine levels and may affect the metabolism of oral hypoglycemic agents and coumadin. Absorption of itraconazole is impaired by antacids, Hj blockers, proton pump inhibitors, and drugs that contain buffers, such as the antiretroviral agent didanosine. 

Serum digoxin levels when compliance, effectiveness, or systemic availability is questioned or toxicity suspected... 

Follow-up care, including monitoring serum digoxin level, is important to maintain... 

Potassium, serum digoxin level prior to therapy... 

McRae S. Elevated serum digoxin levels in a patient taking digoxin and Siberian ginseng. Can Med Assoc J 1996 155 1237-1237. 

Chow L, Johnson M, Wells A, Dasgupta A. Effect of the traditional Chinese medicines Chan Su, Lu-Shen-Wan, Dan Shen, and Asian Ginseng on serum digoxin measurement by Tina-quant (Roche) and Synchron LX system (Beckman) digoxin immunoassays. J Clin Lab Anal 2003 17 22-27. 

Rathbone SS et al Association of serum digoxin concentration and outcomes in patients with heart failure. JAMA 2003 289 871. 

Spironolactone [NE] Decreased renal digoxin excretion and interfers with some serum digoxin assays. 

Doering W, Konig E. [The influence of quinidine on serum digoxin concentrations (author s transl)]. Med Klin 1978 73(30) 1085-1088. 

Mordel A, Halkin H, Zulty L, et al. Quinidine enhancers digitalis toxicity at therapeutic serum digoxin levels. Clin Pharmacol Ther 1993 53 457 -62. 

Leibovitz A, Bilchinsky T, Gil I, Habot B. Elevated serum digoxin level associated with coadministered fluoxetine. Arch Intern Med 1998 158(10) 1152-3. 

Fluoxetine has been reported to increase serum digoxin concentrations (37). 

---