Use of Dietary Supplements by Patients Taking Digoxin: RESULTS part 2

22 Nov
2010

Use of Prescription Medications

The mean number (± standard deviation) of prescription medications, including digoxin, taken during the month before the survey was 7.6 ± 2.8, and the number of concurrent prescription medications ranged from 1 to 17. Almost 90% of the patients (152 or 88.4%) had been exposed to one or more medications with the potential to influence digoxin therapy. The most common concurrent prescription medications of any type were furosemide, spironolactone, carvedilol, and amiodarone; the most common prescription medications with potential interactions with digoxin were also furosemide, spironolactone, carvedilol, and amiodarone (see also Table 3).

Twenty-seven of all participants (15.7%) reported starting a medication known to influence digoxin therapy in the month before the survey. The majority of patients (147 or 85.5%) reported no change in exposure to potentially interacting prescription medications in the past month relative to the past year; 11 (6.4%) reported less exposure and 14 (8.1%) reported more exposure.
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Table 3. Use of Potentially Interacting Medications (Prescription and Nonprescription) and Reporting of Symptoms Potentially Related to Digoxin Toxicity


Use
of Potentially Interacting



Overall Use


No.

(%)

of
Patients with Symptoms



Substance


(No.
and


%

of
Patients)



Potentially Related to Digoxin Toxicity



(n



= 172)


Yes
(n


= 109)


No
(n


= 63)



p

value



Prescription medications other than digoxin


Any


152


(88.4)


99


(90.8)


53


(84.1)


0.19


Furosemide


96


(55.8)


63


(57.8)


33


(52.4)


0.49


Spironolactone


72


(41.9)


48


(44.0)


24


(38.1)


0.45


Carvedilol


61


(35.5)


41


(37.6)


20


(31.7)


0.45


Amiodarone


30


(17.4)


18


(16.5)


12


(19.0)


0.67


Hydrochlorothiazide


13


(7.6)


7


(6.4)


6


(9.5)


0.46


Omeprazole


11


(6.4)


9


(8.3)


2


(3.2)


0.19


Diltiazem


9


(5.2)


2


(1.8)


7


(11.1)


0.008



Nonprescription medications


Use of interacting OTC drug or


nonherbal supplements*t


50


(29.1)


35


(32.1)


15


(23.8)


0.25


Use of interacting OTC drug


(excluding potassium)*t


41


(23.8)


31


(28.4)


10


(15.9)


0.06


Use of potassium supplements


15


(8.7)


8


(7.3)


7


(11.1)


0.40


General use of herbal supplement(s)


in past month


37


(21.5)


23


(21.1)


14


(22.2)


0.86


Use of potentially interacting herbal


supplement(s) in past month


4


(2.3)


3


(2.8)


1


(1.6)


> 0.99


Cassia angustifolia


1


(0.6)


1


(0.9)


0


(0)


> 0.99


Cascara sagrada bark


1


(0.6)


1


(0.9)


0


(0)


> 0.99


Ginseng (any type)


2


(1.2)


2


(1.8)


0


(0)


> 0.99


Licorice root


1


(0.6)


0


(0)


1


(1.6)


> 0.99


OTC =
over-the-counter


*Use of OTC product once per week or more.


tPotentially interacting OTC drugs include antacids, quinine,
kaolin-pectin, and potassium supplements.

Adverse Events Potentially Related to Digoxin or to Drug Interactions

A total of 109 patients (63.4%) reported adverse events potentially related to their digoxin therapy. The most common adverse effect (mentioned by 50 [45.9%] of those reporting adverse events) was changes in vision; other specific symptoms surveyed (e.g., diarrhea, anorexia, nausea) were experienced by about 30% of those with adverse effects. Overall, the majority of patients (155 or 90.1%) reported similar frequency of adverse events in the past month relative to the past year. Patients who had experienced these symptoms in the month before the interview had been receiving digoxin therapy for a shorter period and had been receiving their current dosage for a shorter period than those who did not report these symptoms (Table 4). The 2 groups were similar in terms of all other variables (Table 4). viagra jelly

Table 4. Comparison of Patient Characteristics between Those Who Experienced Symptoms Potentially Related to Digoxin Toxicity and Those Who Did Not



Presence of Symptoms Potentially Related to Digoxin Toxicity*



Characteristic


Yes
(n


= 109)


No
(n


= 63)



p

valuet


Age (years)


64.3±11.8


66.7±12.3


0.22


Duration of digoxin therapy (years)


5.1±6.7


7.3±7.9


0.053


Dose of digoxin (|jg/day)


170±84


183±66


0.32


Duration of current dosage (years)


3.4±4.5


6.0±7.7


0.005


Male sex


75 (68.8)


47 (74.6)


0.49


Impaired renal function


12 (11.0)


5 (7.9)


0.60


Thyroid disorder


19 (17.4)


7 (11.1)


0.38


Malignancy


10 (9.2)


2 (3.2)


0.21


*No. (%)
of patients or mean ± standard
deviation


tStudent’s
t
test for continuous data; x
2
test for dichotomous data.

Table 3 summarizes the use of potentially interacting medications (both prescription and nonprescription) among patients who reported the symptoms specified in the survey and those who did not. Only the 7 most commonly used prescription medications are listed. There was no difference in the use of these prescription medications between those who reported symptoms and those who did not, except for diltiazem (p = 0.008). Furthermore, there were no differences in the use of OTC drugs, nonherbal supplements, and herbal supplements between the 2 groups; however, when potassium supplements were excluded, there was a trend toward greater use of potentially interacting OTC medications among the patients who reported symptoms (p = 0.06).
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