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- unsteady walk
- extreme hunger
- unusual tiredness or weakness
- fast heartbeat
- pale, cool skin
- cold sweats
- dark urine
- yellow skin or eyes
- unusual bleeding or bruising
- heart disorders such as structural heart disease or inflammation of the heart muscle
- congestive heart failure
- kidney disease
- liver disease
- diseases of the blood
- asthma or emphysema
- enlarged prostate or difficulty urinating
- overactive thyroid
- low blood sugar
- myasthenia gravis
- systemic lupus erythematosus
- fever and chills
- difficult urination
- swollen or painful joints
- pain when breathing
- skin rash or itching
- ringing in the ears
- breathing problems
- vision changes
- skin rash
- other heart medicines, including other antiarrhythmic drugs
- blood pressure medicine
- blood thinners
- pimozide (Orap), used to treat Tourette's syndrome
Antiarrhythmic Drugs: Amiodarone Digoxin, Disopyramide, Flecainide, Lidocaine, Procainamide, Quinidine
SpecimenSerum (1 mL) collected in a red-top tube.
|Drug||Route of Administration||Recommended Collection Time|
|Amiodarone||Oral||Trough: immediately before next dose|
|Digoxin||Oral||Trough: 12–24 hr after dose|
|Never draw peak samples|
|Disopyramide||Oral||Trough: immediately before next dose|
|Peak: 2–5 hr after dose|
|Flecainide||Oral||Trough: immediately before next dose|
|Peak: 3 hr after dose|
|Lidocaine||IV||15 min, 1 hr, then every 24 hr|
|Procainamide||IV||15 min; 2, 6, 12 hr; then every 24 hr|
|Procainamide||Oral||Trough: immediately before next dose|
|Peak: 75 min after dose|
|Quinidine sulfate||Oral||Trough: immediately before next dose|
|Peak: 1 hr after dose|
|Quinidine gluconate||Oral||Trough: immediately before next dose|
|Peak: 5 hr after dose|
|Quinidine polygalacturonate||Oral||Trough: immediately before next dose|
|Peak: 2 hr after dose|
|Drug (Indication)||Therapeutic Range Conventional Units||Conversion to SI units||SI Units||Half-Life (hr)||Volume of Distribution (L/kg)||Protein Binding (%)||Excretion|
|Amiodarone||0.5–2.5 mcg/mL||SI units = Conventional Units × 1.55||0.8–3.9 micromol/L||250–1200||20–100||95–97||1° hepatic|
|Digoxin||0.5–2 ng/mL||SI units = Conventional Units × 1.28||0.6–2.6 nmol/L||20–60||7||20–30||1° renal|
|Disopyramide||2.8–7 mcg/mL||SI units = Conventional Units × 2.95||8.3–20.6 micromol/L||4–10||0.7–0.9||20–60||1° renal|
|Flecainide||0.2–1 mcg/mL||SI units = Conventional Units × 2.41||0.5–2.4 micromol/L||7–19||5–13||40–50||1° renal|
|Lidocaine||1.5–5 mcg/mL||SI units = Conventional Units × 4.27||6.4–21.4 micromol/L||1.5–2||1–1.5||60–80||1° hepatic|
|Procainamide||4–10 mcg/mL||SI units = Conventional Units × 4.25||17–42 micromol/L||2–6||2–4||10–20||1° renal|
|N-acetyl procainamide||10–20 mcg/mL||SI units = Conventional Units × 4.25||42–85 micromol/L||8||1° renal|
|Quinidine||2–5 mcg/mL||SI units = Conventional Units × 3.08||6–15 micromol/L||6–8||2–3||70–90||Renal and hepatic|
Many factors must be considered in effective dosing and monitoring of therapeutic drugs, including patient age, patient ethnicity, patient weight, interacting medications, electrolyte balance, protein levels, water balance, conditions that affect absorption and excretion, and the ingestion of substances (e.g., foods, herbals, vitamins, and minerals) that can either potentiate or inhibit the intended target concentration. Peak and trough collection times should be documented carefully in relation to the time of medication administration.
This procedure is contraindicated for
- Assist in the diagnosis and prevention of toxicity
- Monitor compliance with therapeutic regimen
- Monitor patients who have a pacemaker, who have impaired renal or hepatic function, or who are taking interacting drugs
|Normal levels||Therapeutic effect|
|Subtherapeutic levels||Adjust dose as indicated|
|Toxic levels||Adjust dose as indicated|
|Amiodarone||Hepatic impairment, older results|
|Digoxin||Renal impairment, CHF,* older adults|
|Flecainide||Renal impairment, CHF|
|Lidocaine||Hepatic impairment, CHF|
|Quinidine||Renal and hepatic impairment, CHF, older adults|
Adverse effects of subtherapeutic levels are important. Care should be taken to investigate the signs and symptoms of too little and too much medication. Note and immediately report to the HCP any critically increased or subtherapeutic values and related symptoms.
Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. The notification processes will vary among facilities. Upon receipt of the critical finding the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical finding, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.
Signs and symptoms of pulmonary damage related to amiodarone toxicity include bronchospasm, wheezing, fever, dyspnea, cough, hemoptysis, and hypoxia. Possible interventions include discontinuing the medication, monitoring pulmonary function with chest x-ray, monitoring liver function tests to assess for liver damage, monitoring thyroid function tests to assess for thyroid damage (related to the high concentration of iodine contained in the medication), and electrocardiographic (ECG) monitoring for worsening of arrhythmia.
Signs and symptoms of digoxin toxicity include arrhythmias, anorexia, hyperkalemia, nausea, vomiting, diarrhea, changes in mental status, and visual disturbances (objects appear yellow or have halos around them). Possible interventions include discontinuing the medication, continuous ECG monitoring (prolonged P-R interval, widening QRS interval, lengthening Q-Tc interval, and atrioventricular block), transcutaneous pacing, administration of activated charcoal (if the patient has a gag reflex and central nervous system function), support and treatment of electrolyte disturbance, and administration of Digibind (digoxin immune Fab). The amount of Digibind given depends on the level of digoxin to be neutralized. Digoxin levels must be measured before the administration of Digibind. Digoxin levels should not be measured for several days after administration of Digibind in patients with normal renal function (1 wk or longer in patients with decreased renal function). Digibind cross-reacts in the digoxin assay and may provide misleading elevations or decreases in values depending on the particular assay in use by the laboratory.
Signs and symptoms of disopyramide toxicity include prolonged Q-T interval, ventricular tachycardia, hypotension, and heart failure. Possible interventions include discontinuing the medication, airway support, and ECG and blood pressure monitoring.
Signs and symptoms of flecainide toxicity include exaggerated pharmacological effects resulting in arrhythmia. Possible interventions include discontinuing the medication as well as continuous ECG, respiratory, and blood pressure monitoring.
Signs and symptoms of lidocaine toxicity include slurred speech, central nervous system depression, cardiovascular depression, convulsions, muscle twitches, and possible coma. Possible interventions include continuous ECG monitoring, airway support, and seizure precautions.
The active metabolite of procainamide is N-acetyl procainamide (NAPA). Signs and symptoms of procainamide toxicity include torsade de pointes (ventricular tachycardia), nausea, vomiting, agranulocytosis, and hepatic disturbances. Possible interventions include airway protection, emesis, gastric lavage, and administration of sodium lactate.
Signs and symptoms of quinidine toxicity include ataxia, nausea, vomiting, diarrhea, respiratory system depression, hypotension, syncope, anuria, arrhythmias (heart block, widening of QRS and Q-T intervals), asystole, hallucinations, paresthesia, and irritability. Possible interventions include airway support, emesis, gastric lavage, administration of activated charcoal, administration of sodium lactate, and temporary transcutaneous or transvenous pacemaker.
Amiodarone: Greater Than 2.5 mcg/mL (SI: Greater Than 3.9 micromol/L)
Digoxin: Greater Than 2.5 ng/mL (SI: Greater Than 3.2 nmol/L)
Disopyramide: Greater Than 7 mcg/mL (SI: Greater Than 20.6 micromol/L)
Flecainide: Greater Than 1 mcg/mL (SI: Greater Than 2.41 micromol/L)
Lidocaine: Greater Than 6 mcg/mL (SI: Greater Than 25.6 micromol/L)
Procainamide: Greater Than 10 mcg/mL (SI: Greater Than 42.5 micromol/L); N-Acetyl
Procainamide: Greater Than 40 mcg/mL (SI: Greater Than 170 micromol/L)
Quinidine: Greater Than 6 mcg/mL (SI: Greater Than 18.5 micromol/L)
- Blood drawn in serum separator tubes (gel tubes).
- Drugs that may increase amiodarone levels include cimetidine.
- Drugs that may decrease amiodarone levels include cholestyramine and phenytoin.
- Drugs that may increase digoxin levels or increase risk of toxicity include amiodarone, amphotericin B, diclofenac, diltiazem, erythromycin, ibuprofen, indomethacin, nifedipine, nisoldipine, propafenone, propantheline, quinidine, spironolactone, tetracycline, tiapamil, troleandomycin, and verapamil.
- Drugs that may decrease digoxin levels include albuterol, aluminum hydroxide (antacids), carbamazepine, cholestyramine, colestipol, digoxin immune Fab, hydralazine, hydroxychloroquine, iron, kaolin-pectin, magnesium hydroxide, magnesium trisilicate, metoclopramide, neomycin, nitroprusside, paroxetine, phenytoin, rifabutin, sulfasalazine, and ticlopidine.
- Drugs that may increase disopyramide levels or increase risk of toxicity include amiodarone, atenolol, ritonavir, and troleandomycin.
- Drugs that may decrease disopyramide levels include phenobarbital, phenytoin, rifabutin, and rifampin.
- Drugs that may increase flecainide levels or increase risk of toxicity include amiodarone and cimetidine.
- Drugs that may decrease flecainide levels include carbamazepine, charcoal, phenobarbital, and phenytoin.
- Drugs that may increase lidocaine levels or increase risk of toxicity include beta blockers, cimetidine, metoprolol, nadolol, propranolol, and ritonavir.
- Drugs that may decrease lidocaine levels include phenytoin.
- Drugs that may increase procainamide levels or increase risk of toxicity include amiodarone, cimetidine, quinidine, ranitidine, and trimethoprim.
- Drugs that may increase quinidine levels or increase risk of toxicity include acetazolamide, amiodarone, cimetidine, itraconazole, mibefradil, nifedipine, nisoldipine, quinidine, ranitidine, thiazide diuretics, and verapamil.
- Drugs that may decrease quinidine levels include kaolin-pectin, ketoconazole, phenobarbital, phenytoin, rifabutin, and rifampin.
- Concomitant administration of amiodarone with other medications may result in toxic levels of the other medications related to the suppression of enzyme activity required to metabolize many other medications by amiodarone. It may also potentiate the anticoagulating effects of warfarin, resulting in increased PT values.
- Digitoxin cross-reacts with digoxin; results are falsely elevated if digoxin is measured when the patient is taking digitoxin.
- Digitalis-like immunoreactive substances are found in the serum of some patients who are not taking digoxin, causing false-positive results. Patients whose serum contains digitalis-like immunoreactive substances usually have a condition related to salt and fluid retention, such as renal failure, hepatic failure, low-renin hypertension, and pregnancy.
- Unexpectedly low digoxin levels may be found in patients with thyroid disease.
- Disopyramide may cause a decrease in glucose levels. It may also potentiate the anticoagulating effects of warfarin, resulting in increased PT values.
- Long-term administration of procainamide can cause false-positive antinuclear antibody results and development of a lupuslike syndrome in some patients.
- Quinidine may potentiate the effects of neuromuscular blocking medications and warfarin anticoagulants.
- Concomitant administration of quinidine and digoxin can rapidly raise digoxin to toxic levels. If both drugs are to be given together, the digoxin level should be measured before the first dose of quinidine and again in 4 to 6 days.
Nursing Implications and Procedure
- Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
- Patient Teaching: Inform the patient this test can assist in monitoring for subtherapeutic, therapeutic, or toxic drug levels.
- Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
- Obtain a history of the patient’s cardiovascular system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
- These medications are metabolized and excreted by the kidneys and liver.
- Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus). Note the last time and dose of medication taken.
- Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
- Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
- Note that there are no food, fluid, or medication restrictions unless by medical direction.
- Potential complications: N/A
- Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
- Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
- Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Consider recommended collection time in relation to the dosing schedule. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection, noting the last dose of medication taken. Perform a venipuncture.
- Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
- Promptly transport the specimen to the laboratory for processing and analysis.
- Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
- Nutritional Considerations: Include avoidance of alcohol consumption.
- Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Explain to the patient the importance of following the medication regimen and instructions regarding drug interactions. Instruct the patient to immediately report any unusual sensations (e.g., dizziness, changes in vision, loss of appetite, nausea, vomiting, diarrhea, weakness, or irregular heartbeat) to his or her HCP. Instruct the patient not to take medicine within 1 hr of food high in fiber (as the fiber may decrease absorption by binding some of the medication, reducing its bioavailability). Answer any questions or address any concerns voiced by the patient or family.
- Instruct the patient to be prepared to provide the pharmacist with a list of other medications he or she is already taking in the event that the requesting HCP prescribes a medication.
- Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Testing for aspirin responsiveness/resistance may be a consideration for patients, especially women, on low-dose aspirin therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
- Related tests include ALT; albumin; ALP; apolipoproteins A, B, and E; AST; atrial natriuretic peptide; BNP; blood gases; BUN; CRP; calcium; calcium ionized; chest x-ray; cholesterol (total, HDL, and LDL); CBC platelet count; CK and isoenzymes; creatinine; ECG; glucose; glycated hemoglobin; homocysteine; ketones; LDH and isoenzymes; magnesium; myoglobin; potassium; triglycerides; and troponin.
- See the Cardiovascular System table at the end of the book for related tests by body system.