<p>Which of the drugs qualifies as a partial agonist?</p><p>Drug C: even at the highest concentration, only a fraction of the maximal response can be achieved</p><p>A patient appears in the emergency room with a history of ingesting vinegar at a party where marijuana was smoked. The pH of his urine was found to be 2.0. What effect would this pH have had on 11-nor delta9-THC carboxylic acid (THC- COOH), a weak acid metabolite of marijuana? A. the THC-COOH would be ionized B. the concentration of THC-COOH in urine would be decreased C. the concentration of THC-COOH in urine would be increased D. the excretion of THC-COOH would be facilitated E. none of the above </p><p>B. the concentration of THC-COOH in urine would be decreased: Lowering the pH of the urine (increasing urine H ion concentration) would increase the percentage of THC that is unionized (e.g. THC-COO- + H+ -> THC- COOH). This will increase passive re-absorption of the drug (lack of “trapping” in the urine) across cell membranes in the kidney, and lower the amount that stays in the renal filtrate (urine). The full effect of digoxin in slowing the heart rate after a single i.v. dose may require 6-8 hours to develop. Which of the following is the most likely explanation? A. rapid renal clearance B. long distribution phase C. extensive protein binding D. long elimination half-life E. small volume of distribution</p><p>B. long distribution phase: It takes 6-8 hours for digoxin in the plasma to equlibrate (distribute into) peripheral tissues such as the heart. Thus the peak effect is delayed after giving a loading dose of digoxin </p><p>Phenobarbital and warfarin were administered together to a patient with a myocardial infarction over a period of 7 days. During this time, the warfarin dosage was adjusted to get a 20% increase in coagulation time. On day 8, the patient discontinued the phenobarbital but continued to take the warfarin for the next 2 weeks. What effect would be expected with respect to warfarin? A. plasma level would be increased B. plasma level would be decreased C. prothrombin time would be decreased D. warfarin binding to plasma protein would be decreased A. plasma level would be increased: Phenobarbital is a good inducer of cytochrome P-450, a major drug-metabolizing enzyme. Discontinuation of phenobarbital will result in a decrease in this effect, lower levels of drug-metabolizing enzymes, and increased plasma levels of warfarin .Eliminating phenobarbital would also not decrease the amount of warfarin binding to plasma proteins. </p>