Exam 2005 (A) - PHA 5515 Exam Form A Total 120 points Read...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: PHA 5515 April 13, 2005 Exam Form A Total: 120 points Read each question carefully before answering. Answer only the question that is written on the page; don’t add any of your own parts to it. Remember the Academic Dishonesty Policy; keep your eyes on your own paper. Please turn in the test and answer sheets when you have finished. Good Luck! True/False (2 pt) Phenobarbital, phenytoin, carbamazepine, ethoxsuximide and valproate (Depakote®) are some commonly used anti-epileptic drugs. Phenytoin and carbamazepine are selectively effective in treating patients with tonic-clonic seizures while ethoxsuximide is selectively effective in treating absence seizures. Valproate and phenobarbital are effective in decreasing the incidence of both tonic-clonic and absence seizures (Figures 1 and 2). You suspect that these efficacies are based on the ability of these drugs to block either voltage-sensitive calcium (CA) or sodium (NA) channels in the brain. Therefore you measure and compare the efficacies and potencies of these drugs to displace the specific binding of 3 H-valproate from these ion channels in homogenized brain samples. Which of the following conclusions would be valid after examining the resulting competition curves shown in Figure 3? 1. Valproate and phenobarbital can bind to both CA and NA channels but the IC 50 values for the two subtypes are more alike for valproate than they are for phenobarbital. 2. Ethoxsuximide can not bind specifically to any valproate receptors at nanomolar concentrations. 3. About one third of the binding sites occupied by 3 H-valproate also bind phenytoin and carbamazepine (the NA channels) while the other two thirds of the receptors only bind ethoxsuximide (the CA channels). 4. Ethoxsuximide would be able to compete for at least a portion of specific binding if a competition curve were performed using 3 H- phenytoin as the radiolabeled drug. 5. Phenobarbital would be able to compete for at least a portion of specific binding if a competition curve were performed using 3 H-carbamazepine as the radiolabeled drug. 6. Valproate clearly has a lower affinity for the CA channel site compared to its affinity for the NA channel site. 7. You would suspect that 66% of the valproate receptors (CA channels) are involved in the effects of these drugs on absence seizures. 8. You would suspect that 34% of the valproate receptors (NA channels) are involved in the effects of these drugs on tonic-clonic seizures. 9. Phenobarbital is an agonist at the inhibitory binding site on the NA channels. 10. Ethoxsuximide is a partial agonist at the inhibitory site on the CA channels. 11. Valproate clearly has a lower affinity for the CA channel site compared to ethoxsuximide’s affinity for the CA channel site. 20 40 60 80 100 0.01 0.03 0.1 0.3 1 3 10 30 100 300 1000 3000 Drug Dose (mg) Efficacy against tonic-clonic seizures phenobarb....
View Full Document

{[ snackBarMessage ]}

Page1 / 15

Exam 2005 (A) - PHA 5515 Exam Form A Total 120 points Read...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online