Phenytoin and Fosphenytoin

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Questions and Answers

Which dosage form of phenytoin has a salt factor of 0.92?

Capsule (correct)
Injection
Suspension
Chewable tablets

What is the concentration range for minor CNS depression caused by phenytoin?

15-20 ug/mL (correct)
40-50 ug/mL
20-30 ug/mL
30-40 ug/mL

At what concentration range does ataxia, slurred speech, and incoordination occur as a result of phenytoin toxicity?

50-60 ug/mL
30-40 ug/mL (correct)
20-30 ug/mL
40-50 ug/mL

What concentration range is associated with mental status change, severe confusion and lethargy, and coma due to phenytoin toxicity?

50-60 ug/mL (A) Signup and view all the answers

Which dosing method should take into consideration the salt factor of phenytoin?

Changing dosage form (D) Signup and view all the answers

Phenytoin is primarily used for the treatment of which type of seizures?

Tonic-clonic seizures (C) Signup and view all the answers

What is the mechanism of action of phenytoin?

Inhibition of sodium ion channels (B) Signup and view all the answers

What is the main difference between phenytoin and fosphenytoin formulations?

Fosphenytoin is rapidly converted to phenytoin, while phenytoin is not (A) Signup and view all the answers

What is the equation for the pharmacokinetics of phenytoin?

$\frac{\text{dx}},{\text{dt}} = \frac{V_{\max}\text{\ x\ }C_{\text{ss}}},{K_{m} + C_{\text{ss}}}$ (B) Signup and view all the answers

What is the main difference between Vmax and Km?

Vmax is the maximum rate of drug metabolism, while Km is the drug concentration at which the rate of metabolism is half of Vmax (D) Signup and view all the answers

Which equation is used to calculate body mass index (BMI)?

$\frac{Total\ Body\ weight\ (kg)},{\text{Heigh}t^{2}(meters)}$ (B) Signup and view all the answers

Which of the following BMI ranges corresponds to normal weight?

Normal weight: 18.5 – 24.99 kg/m2 (C) Signup and view all the answers

What is the equation for calculating body surface area (BSA)?

$\sqrt{\frac{\text{height\ }\left( \text{cm} \right) \times \ weight\ (kg)},{3600}}$ (A) Signup and view all the answers

When is a patient considered morbidly obese based on BMI?

Obesity Class III (morbid obesity): > 40 kg/m2 (C) Signup and view all the answers

What is the equation for calculating ideal body weight (IBW) for males?

50 kg + 2.3 kg (inches > 5 feet) (B) Signup and view all the answers

What is the equation for calculating adjusted body weight (ABW) using a correction factor of 0.4?

ABW = IBW + 0.4 (C) Signup and view all the answers

What is the purpose of adjusted body weight (ABW) calculations?

To determine the dosage of aminoglycosides (B) Signup and view all the answers

Which equation represents the calculation for adjusted body weight (ABW)?

ABW = IBW + (TBW - IBW) (A) Signup and view all the answers

What is the impact of obesity on hepatic drug clearance?

Obesity has no impact on hepatic drug clearance (B) Signup and view all the answers

Which type of drugs may show an increase, decrease, or no change in plasma protein binding in obesity?

Drugs primarily bound to α1-acid glycoprotein (D) Signup and view all the answers

What is the equation for renal clearance?

Renal clearance = Glomerular filtration rate (GFR) - Tubular secretion + Tubular reabsorption (A) Signup and view all the answers

What are the physiological changes in obesity that affect drug distribution?

Increased plasma protein binding and increased adipose tissue mass (B) Signup and view all the answers

What is the equation for predicting changes in volume of distribution for hydrophilic (polar) compounds in obese individuals?

Vd = Same as in non-obese individuals (B) Signup and view all the answers

What is the impact of obesity on the half-life of phenytoin in obese patients compared to normal weight patients?

The half-life of phenytoin is longer in obese patients (A) Signup and view all the answers

What is the impact of obesity on the volume of distribution of lithium in obese individuals compared to non-obese individuals?

The volume of distribution of lithium is lower in obese individuals (A) Signup and view all the answers

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