FIGURE 5. If resistance to furosemide results or other factors (eg, a high salt meal) dictate that more diuresis is needed, 1 of 2 strategies may be used: First is to administer a higher dosage, as shown with the red pharmacodynamic curve. The increase in dosage increases the urine level of the diuretic but provides only a small increase in time in the effective range, enhancing diuresis (red arrow) but increasing risk for toxicity. A better approach, although problematic in terms of owner compliance, is to administer multiple doses throughout the day. As shown in this figure, administering the same dosage 3 times triples the time in the effective range and avoids the risk for toxicity.
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