suppress fast rhythms of the heart ( cardiac arrhythmias ), such as atrial fibrillation , atrial flutter , ventricular tachycardia , and ventricular fibrillation . It is important to stress that these medications do NOT cure the underlying cause of an arrhythmia Normal: depending on your age and physical conditioning 60-80 bpm Tachcarydia: 150-250 bpm Bradycardia: < 60 bpm Irregular heart beat due to extra beats or fibrillation
Antiarrhythmic drugs are grouped into 4 classes using the Vaughan Williams classification , introduced in 1970 Drugs are classfied based on its primary mechanism of its antiarrhythmic effect. However, one of the limitations of the VW classifcations, is that many antiarrhtmic agenst have MULTIPLE MOAs Arrythmias, hypertension, heart failure or myocardial infarctions
sodium, and magnesium levels. Low potassium and magnesium levels can lead to heart rhythm abnormalities, especially in patients already taking digoxin (Lanoxin). Please visit the digoxin (Lanoxin) site for further information.
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competitive inhibitor at autonomic postganglionic cholinergic receptors
↓ in salivary bronchial, & sweat gland secretions; mydriasis; cycloplegia; changes in heart rate; contraction of the bladder detrusor muscle and of the GI smooth muscle; ↓ gastric secretion; and ↓ GI motility
Initially, 800-1600 mg/day PO in single or divided doses for a minimum of 1-3 weeks in a monitored setting until an initial therapeutic response is achieved
followed by 600-800 mg/day PO in one or divided doses for about one month.
Then reduce dosage again to the lowest effective maintenance dose, usually 400 mg/day PO in one or divided doses
initial IV rapid infusion of 150 mg over the first 10 minutes. Then begin a slow IV infusion of 1 mg/min for the next 6 hours (total dose infused = 360 mg). Then, the infusion rate is lowered to 0.5 mg/min for the next 18 hours (total dose infused = 540 mg). After the first 24 hours, a maintenance IV infusion of 0.5 mg/minute (720 mg/day) is recommended.
Cardiovascular: exacerbation of the arrhythmias, CHF (3%) and bradycardia. Cardiac arrhythmias, CHF, sinoatrial node dysfunction (1% to 3%); cardiac conduction abnormalities, hypotension (less than 1%)
CNS: 20% to 40% of patients and including malaise and fatigue, peripheral neuropathy, poor coordination & gait, & tremor and involuntary movements; they are rarely a reason to stop therapy and may respond to dose reductions or discontinuation; Abnormal gait/ataxia, dizziness, lack of coordination, malaise and fatigue, paresthesias, tremor/abnormal involuntary movements (4% to 9%); decreased libido, headache, insomnia, sleep disturbances (1% to 3%).
Dermatologic: ~ 15% of patients, with photosensitivity being most common (approximately 10%). Sunscreen and protection from sun exposure may be helpful, and drug discontinuation is not usually necessary. Prolonged exposure to amiodarone occasionally results in a blue-gray pigmentation; Solar dermatitis/photosensitivity (4% to 9%); alopecia, blue skin discoloration, rash, spontaneous ecchymosis (less than 1%).
Endocrine: Hyperthyroidism, hypothyroidism (1% to 3%).
GI: GI complaints, most commonly anorexia, constipation, N/V (10% to 33%); anorexia, constipation (4% to 9%); abdominal pain (1% to 3%)
Hepatic: Abnormal liver function tests (4% to 9%); nonspecific hepatic disorders (1% to 3%)
Ophthalmic: optic neuropathy and/or optic neuritis, in some cases progressing to corneal degeneration, eye discomfort, lens opacities, macular degeneration, papilledema, permanent blindness, photosensitivity, and scotoma, have been reported . Asymptomatic corneal microdeposits are present in virtually all adult patients who have been on the drug for more than 6 months. Some patients develop eye symptoms of dry eyes, halos, and photophobia. Vision is rarely affected and drug discontinuation is rarely needed. Visual disturbances (4% to 9%)
Respiratory: Fibrosis, pulmonary inflammation (4% to 9%)
Miscellaneous: Abnormal salivation, abnormal taste and smell, coagulation abnormalities, edema, flushing (1% to 3%).
Diuretic Properties Diuretic agent Site of Action & Misc. Chlorothiazide PO/IV Distal Tubule Calcium Reabsorption Increased May transiently increase Lipids, BG and UA Hypomagnesemia (may complicate K+ correction) Severe Potassium Depletion – Creation of Combos ??? Pregnancy categories: B and C Hydrochlorothiazide Indapamide Metolazone (Mykrox) Furosemide Ascending Limb of Henle Ototoxocity (reversible and irreversible) Hypokalemia (supplement with K+) Pregnancy categories: B Torsemide Bumetanide Ethacrynic acid Amiloride Distal and Proximal tubule Impact Hyperkalemia and serum creatinine elevations Avoidance: BUN > 30 mg/dl or SCr > 1.5 mg/dl Triamterene Eplerenone Distal and Aldosterone receptor Impact Same as amiloride and triamterene – avoid K spare combos Spironolactone
po : Initially, 20-80 mg as a single dose; may repeat dose in 6-8 hr. Titrate upward in 20-40 mg increments. The usual dosage is 40-120 mg/day. Max dosage is 600 mg/day.
IV or IM : Initially, 20-40 mg, increasing by 20 mg every 2 hours prn to attain clinical response. Administer IV doses slowly. A max infusion rate of 4 mg/min has been recommended when administering doses >120 mg or for patients with cardiac or renal failure
In February 2008 , the FDA issued a MedWatch in response to an increase in the number of serious adverse events including allergic or hypersensitivity-type reactions with the administration of higher bolus doses of heparin. The reports have mainly involved the use of Baxter multiple-dose vials ; however, there have been reports of these reactions occurring when the combination of multiple- and single-dose vials have been used to administer a bolus dose. In February 2008, Baxter International announced expanding their voluntary recall to include all lots and doses of its Heparin Sodium UPS multi-dose, single-dose vials, and HEP-LOCK heparin flush products . The company initially recalled nine lots of heparin sodium injection multi-dose vials as a precautionary measure due to a higher than usual number of reports of adverse patient reactions involving the product. In March 2008, the FDA announced that the contaminant found in samples of Baxter's heparin was oversulfated chondroitin sulfate, a substance derived from animal cartilage. The FDA also stated that it does not know whether this contaminant caused the adverse events, only that a contaminant has been identified . Investigations continue as to whether this contaminant was added to heparin by accident or intentionally. Customers with questions regarding the Baxter recall may contact the Center for One Baxter at 1-800-422-9837.
Warfarin can cause major or fatal bleeding . Bleeding is more likely to occur during the starting period and with a higher dose (resulting in a higher international normalized ratio [INR]). Risk factors for bleeding include high intensity of anticoagulation (INR of more than 4), 65 years of age and older, highly variable INRs, history of GI bleeding, hypertension, cerebrovascular disease, serious heart disease, anemia, malignancy, trauma, renal function impairment, concomitant drugs, and long duration of warfarin therapy. Regular monitoring of INR should be performed on all treated patients . Those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shorter duration of therapy. Patients should be instructed about prevention measures to minimize risk of bleeding and to report immediately to health care provider signs and symptoms of bleeding
Hemorrhage: Signs of severe bleeding resulting in the loss of large amounts of blood depend upon the location and extent of bleeding. Symptoms include: chest, abdomen, joint, muscle, or other pain; difficult breathing or swallowing; dizziness; headache; low blood pressure; numbness and tingling; paralysis; shortness of breath; unexplained shock; unexplained swelling; weakness