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Document<br />

12<br />

Polypeptide Modulators of Sodium Channel Function as a Basis for the<br />

Development of Novel Cardiac Stimulants<br />

Raymond S. Norton<br />

Biomolecular Research Institute, Parkville, Victoria, Australia<br />

I. Introduction<br />

Page 295<br />

Cardiovascular diseases remain one of the major causes of premature death in western societies. Chronic<br />

congestive heart failure (CHF) in particular is a common disease with a poor prognosis, median survival<br />

times after the onset of heart failure being 1.7 years in men and 3.2 years in women [1]. Current<br />

treatment relies on diuretics to reduce fluid volume, vasodilators to decrease the work load of the heart,<br />

and positive inotropic agents to increase cardiac contractility [2]. The most commonly prescribed of the<br />

positive inotropes is the cardiac glycoside digoxin (Figure 1) [3]. Although this drug has been in<br />

therapeutic use for over two hundred years, its efficacy in patients with a sinus rhythm has remained<br />

controversial, and evidence for its beneficial effects is quite recent [3–5]. It is also possible that these<br />

beneficial effects are not due solely to the positive inotropic activity of digoxin and that its<br />

neurohormonal effects may also be important [2, 5–7] Nevertheless, digoxin remains a widely used drug<br />

[3] and it follows that a suitable replacement or adjunct would find access to a significant market<br />

worldwide.<br />

The incentive to develop such a replacement follows from the low therapeutic index of digoxin [8,9] and<br />

the relatively common occurrence of side effects due to digitalis toxicity. In the 1960s and 1970s,<br />

20–30% of patients receiving digitalis experienced serious toxicity and about one quarter of this group<br />

died [6, 10]. Digitalis toxicity is manifest in CNS side-effects such as<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_295.html [4/5/2004 5:17:59 PM]

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