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Glomerular filtration rate – While GFR is a key measure of kidney function, it is often estimated based on creatinine clearance rather than measured directly in routine practice. Direct creatinine clearance testing is more precise in this setting.

Urine specific gravity – This measures urine concentration and hydration status but does not accurately evaluate overall renal function or filtration capacity.

Urine pH – This indicates the acidity or alkalinity of urine, which can help in diagnosing some metabolic or urinary disorders, but it does not reflect kidney filtration efficiency.

“To achieve drug action, drugs are moved by four processes.” – This describes the pharmacokinetic phase, which involves absorption, distribution, metabolism, and excretion, not the pharmaceutic phase.

“For the drug to cross the biologic membrane, the drug becomes a solution.” – While dissolution into a solution is part of the pharmaceutic phase, this statement focuses only on one step and does not capture the full definition of the phase.

“In this phase, drugs are concentrated and a biologic or physiologic response occurs.” – This describes the pharmacodynamic phase, where the drug interacts with receptors to produce effects, not the pharmaceutic phase.

Twice a day – Unnecessary for a drug with such a prolonged half-life, as this could lead to excessive drug accumulation and an increased risk of sedation or toxicity.

Three times a day – Appropriate for short-acting medications but not for long-acting barbiturates like phenobarbital.

Four times a day – This frequent dosing is used for drugs with very short half-lives; with phenobarbital, it would cause dangerously high plasma drug levels and adverse effects.

Oral – Drugs taken orally are absorbed through the GI tract and pass through the liver via the portal circulation, undergoing extensive first-pass metabolism, which reduces bioavailability. This is not ideal for patients with significant liver impairment.

Rectal – While partial absorption from the lower rectum can bypass the liver, a significant portion of rectal blood flow still goes through the portal vein, meaning some first-pass metabolism still occurs.

Sustained-release oral tablet – Although it provides slow, steady drug release, it is still absorbed in the GI tract and subject to the first-pass effect, making it unsuitable for avoiding reduced bioavailability in this scenario.

It reduces the drug’s potency, decreasing risk of toxicity – Crushing does not inherently reduce drug potency; instead, it can lead to faster absorption and possibly increased toxicity if the entire dose is released at once.

It ensures the drug is dissolved only in acidic pH environments – Enteric coatings are made to dissolve in alkaline, not acidic, environments. This statement reflects a misunderstanding of the drug’s design.

It eliminates the possibility of delayed absorption – While crushing can speed absorption, the primary concern is loss of targeted release and site-specific absorption, not just timing.

It refers only to the rate of GI drug dissolution – Bioavailability involves both the rate and extent of absorption into systemic circulation, not just GI dissolution.

Oral drugs generally have bioavailability close to 100% – Most oral drugs have less than 100% bioavailability due to incomplete absorption and first-pass metabolism in the liver.

The first-pass effect increases oral bioavailability – The first-pass effect decreases oral bioavailability because a portion of the drug is metabolized in the liver before reaching systemic circulation.

Decreased drug effect due to more binding – Low albumin leads to less binding, not more. This would increase, not decrease, the drug’s effect.

Accelerated liver metabolism – Albumin levels do not directly influence liver metabolism. The liver processes drugs based on enzyme activity, not plasma protein levels.

Delayed renal elimination – While protein binding can affect filtration, low albumin primarily impacts drug distribution, not elimination rate.