Which time frame describes the onset of action for intravenous (IV) heparin?

Immediate

5 to 10 minutes

20 minutes

1 hour

Answer and Explanation

The Correct Answer is A

Choice A reason: Intravenous heparin has an immediate onset, as it rapidly enhances antithrombin activity, inhibiting thrombin and factor Xa, preventing clot formation. This quick action makes it ideal for acute conditions like pulmonary embolism, providing instant anticoagulation, with effects measurable by aPTT within minutes of administration.

Choice B reason: A 5- to 10-minute onset is too slow for IV heparin, which acts immediately upon entering the bloodstream. Subcutaneous heparin has a delayed onset (20-60 minutes), but IV delivery ensures rapid anticoagulant effects, making this timeframe incorrect for IV administration.

Choice C reason: A 20-minute onset is inaccurate for IV heparin. Its immediate binding to antithrombin provides instant anticoagulation, unlike oral anticoagulants like warfarin, which take days. The 20-minute timeframe may apply to subcutaneous heparin, not IV, which acts within seconds to minutes.

Choice D reason: A 1-hour onset is incorrect for IV heparin, which provides immediate anticoagulation by enhancing antithrombin’s inhibition of clotting factors. This rapid action is critical for acute thrombotic conditions. A 1-hour delay applies to drugs with slower absorption, not IV heparin’s direct action.

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Correct Answer is A

Explanation

Choice A reason: Warfarin overdose causes excessive anticoagulation, increasing bleeding risk by inhibiting vitamin K-dependent clotting factors (II, VII, IX, X). Vitamin K reverses this by restoring clotting factor synthesis, correcting INR and stopping gastrointestinal bleeding, making it the standard treatment for warfarin toxicity.

Choice B reason: Vitamin E has no role in reversing warfarin toxicity. It is an antioxidant with no effect on clotting factor synthesis or warfarin’s mechanism. Its use may be associated with bleeding risk in high doses, making it inappropriate for managing warfarin-induced gastrointestinal bleeding.

Choice C reason: Protamine sulfate reverses heparin, not warfarin. Heparin enhances antithrombin activity, and protamine neutralizes it. Warfarin’s effect on vitamin K-dependent factors is unrelated, and protamine has no impact on warfarin toxicity or gastrointestinal bleeding, making it an incorrect choice.

Choice D reason: Potassium chloride treats hypokalemia, not warfarin toxicity. Warfarin’s bleeding complications result from inhibited clotting factor synthesis, not electrolyte imbalances. Potassium chloride is irrelevant to reversing anticoagulation or managing gastrointestinal bleeding caused by excessive warfarin, making this an inappropriate treatment.

A. Tendonitis and tendon rupture B. Hypotension and tachycardia C. Double vision and floaters D. Numbness and tingling

Correct Answer is A

Explanation

Choice A reason: Levofloxacin, a fluoroquinolone, is associated with tendonitis and tendon rupture, particularly in older adults. It disrupts collagen synthesis, weakening tendons like the Achilles, especially in patients over 60 or on corticosteroids. Monitoring for tendon pain is critical to prevent debilitating injury during therapy.

Choice B reason: Hypotension and tachycardia are not primary adverse effects of levofloxacin. Fluoroquinolones may cause QT prolongation, but cardiovascular effects are rare. Their main toxicities include tendon damage and CNS effects, making this an incorrect choice for monitoring in this patient.

Choice C reason: Double vision and floaters are not typical levofloxacin side effects. Fluoroquinolones may cause CNS effects like dizziness or confusion, but visual disturbances like these are more associated with drugs like chloroquine. Tendon issues are a more significant concern with levofloxacin.

Choice D reason: Numbness and tingling are not common with levofloxacin. While fluoroquinolones can cause CNS side effects like seizures in rare cases, peripheral neuropathy is less frequent. Tendonitis and rupture are more prominent risks, especially in older patients, making this an incorrect monitoring priority.

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Which time frame describes the onset of action for intravenous (IV) heparin?

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Naxlex Comprehensive Predictor Exams

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Correct Answer is A

Explanation

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Correct Answer is A

Explanation

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