Cardiac glycosides causing

Cardiac glycosides cause a positive inotropic effect which means an increase of the cardiac beat volume by enhanced contraction ability. The reason for this is supposed to be aligned with the direct inhibition of the transport enzyme sodium/ potassium-ATPase. The decrease of sodium ions enhances the calcium ion concentration, which activates the myofibrillic enzyme and inactivates proteins like tropo-myocine and tropomine. Till present, a final proof for this hypothesis is lacking, the toxicity, however, is definitely aligned with these effects [97]. 

Other factors may exhibit synergism in reactions with contrast media. In mice, contrast media with cardiac glycoside cause higher mortality than contrast media alone (593). Incompatibility of contrast media with other pharmacological agents has also been noted... 

In addition, through an effect in the central nervous system cardiac glycosides cause an increase in parasympathetic activity and therefore slow conduction through the AV node, hence their usefulness in atrial flutter and atrial fibrillation. 

The mechanism whereby cardiac glycosides cause a positive inotropic effect and electrophysiological changes is still not completely known despite years of active investigation. Several mechanisms have been proposed, but the most widely accepted mechanism involves the ability of cardiac glycosides to inhibit the membrane-bound Na /K -adenosine triphosphatase (Na /K -ATPase) pump responsible for sodium/potassium exchange. To understand better the correlation between the pump and the mechanism of action of cardiac glycosides on the heart muscle contraction, one has to consider the sequence of events associated with cardiac action potential that ultimately leads to muscular contraction. The process of membrane depolarization/repolarization is controlled mainly by the movement of the three ions, Na", K", Ca ", in and out of the cell. 

Ephedra (sea grape, ma-huang, yellow horse) ephedra sinica Relieves colds, improves respiratory function, headaches, diuretic effects 3heart rate, psychosis l hedra should only be used after consulting with the physician. Many restrictions apply and the herb can cause serious reactions. Do not use with cardiac glycosides, monoamine oxidase inhibitor halothane, guanethidine, (MAOIs) or oxytocin. Do not use with 3. John s wort or in weight loss formulas. 

Parenteral therapy The dangers of parenteral use of quinidine are increased in the presence of AV block or absence of atrial activity. Administration is more hazardous in patients with extensive myocardial damage. Use of quinidine in digitalis-induced cardiac arrhythmia is extremely dangerous because the cardiac glycoside may already have caused serious impairment of intracardiac conduction system. Too rapid IV administration of as little as 200 mg may precipitate a fall of 40 to 50 mm Hg in arterial pressure. 

Mannitol (OsmitroL others) [Osmotic Diuretic] Uses Cerebral edema, T lOP/ICP, renal impair, poisonings Action Osmotic diuretic Dose Test dose 0.2 g/kg/dose IV over 3-5 min if no diuresis w/in 2 h, D/C Oliguria 50-100 g IV over 90 min T lOP 0.5-2 g/kg IV over 30 min Cerebral edema 0.25-1.5 g/kg/dose IV >30 min Caution [C, ] w/ CHF or volume overload Contra Anuria, dehydration, HE, PE Disp Inj SE May exacerbate CHF, N/V/D Interactions t Effects OF cardiac glycosides X effects OF barbiturates, imipramine, Li, salicylates EMS Monitor ECG for hypo-/hyperkalemia (T wave changes) OD May cause dehydration, t urine frequency/amount hypotension and CV collapse symptomatic and supportive... 

The side-effects of cardiac glycosides are mostly caused by electrophysiological/neuronal phenomena. Gastro-intestinal adverse reactions are probably triggered by effects on the central nervous system. Various types of cardiac arrhythmias are caused by the influence of the drugs on nodal tissues in the heart. The risk of arrhythmia is strongly enhanced by low plasma potassium concentrations. 

Cardiac glycosides increase contraction of the cardiac sarcomere by increasing the free calcium concentration in the vicinity of the contractile proteins during systole. The increase in calcium concentration is the result of a two-step process first, an increase of intracellular sodium concentration because of Na+,K+ ATPase inhibition and second, a relative reduction of calcium expulsion from the cell by the sodium-calcium exchanger (NCX in Figure 13-1) caused by the increase in intracellular sodium. The increased cytoplasmic calcium is sequestered by SERCA in the SR for later release. Other mechanisms have been proposed but are not well supported. 

Cardiac glycosides affect all excitable tissues, including smooth muscle and the central nervous system. The gastrointestinal tract is the most common site of digitalis toxicity outside the heart. The effects include anorexia, nausea, vomiting, and diarrhea. This toxicity is caused in part by direct effects on the gastrointestinal tract and in part by central nervous system actions. 

Cholecalciferol [Vitamin D3] (Delta D) [Vitamin/Dietary Supplement] Uses Dietary supl to Rx vit D deficiency Action T Intestinal Ca2+ absorption Dose 400-1000 Int Units/d PO Caution [A (D doses above the RDA), +] Contra T Ca2+, hypervitaminosis, allergy Disp Tabs SE Vit D tox Interactions T Risk of arrhythmias w/ cardiac glycosides X effects w/ cholestyramine, colestipol, mineral oil, orlistat, phenobarbital, phenytoin EMS Can cause vit D tox (Tin serum Ca2+ weakness, AMS, Gl upset and cardiac arrhythmias) OD May cause T risk of vitD tox give IV fluids... 

Uses Acute CHF, ischemic cardiomyopathy Action Inotrope w/ vasodilator Dose IV bolus 0.75 mg/kg over 2-3 min maint 5-10 mcg/kg/min, 10 mg/kg/d max i if CrCl <10 mL/min Caution [C, ] Contra Bisulfite allergy Disp Inj SE Monitor fluid, electrolyte, renal changes Interactions Diuretics cause significant hypovolemia T effects OF cardiac glycosides EMS Avoid diuretic use, can cause profound hypovolemia incompatible w/ dextrose solns monitor ECG for hypokalemia (flattened T waves) OD May cause profound hypotension use IV fluids w/ caution d/t fluid buildup in lungs, pressors may be used... 

---