Question 11#

Flumazenil can reverse the effects of an overdose of which of the following drugs?

A. Opioids

C. Flumazenil is an antagonist of benzodiazepine receptors at the GABAA complex. It is used to reverse sedative effects of benzodiazepines used in anaesthesia and in management of benzodiazepine overdose. As a result of this effect, it can precipitate benzodiazepine withdrawal seizures and can also precipitate anxiety in patients with anxiety/ panic disorder. It is not used to treat benzodiazepine withdrawal symptoms. It is not useful for any other drug toxicity or abuse as mentioned in the question. Naloxone is used in opioid overdose.

Reference:

1. Taylor et al., eds. The Maudsley Prescribing Guidelines, 8th edn. Taylor and Francis, 2005, p. 317

Question 12#

Regarding depot preparations, which of the following statements is FALSE?

A. Depot medications are useful in cases of non-compliance

E. Depot antipsychotic drugs have the following advantages: they decrease the risk of problems associated with medication non-compliance and undergo significantly less first-pass metabolism. The disadvantages include the fact that, once injected, the drug cannot be removed and hence adverse effects or adverse drug interactions are less reversible. An associated complication is injection site reaction. Depot risperidone is an aqueous suspension of risperidone in a glycolic acid–lactate copolymer matrix. The copolymer is slowly hydrolysed, resulting in the gradual release of risperidone. As depot risperidone is water based, it causes fewer reactions than the other oil-based preparations.

Reference:

1. Grant S and Fitton A. Risperidone: a review of its pharmacology and therapeutic potential in the treatment of schizophrenia. Drugs 1994; 48: 253–273.

Question 13#

Which one of the following is NOT a CYP3A4 inducer?

A. St. John’s wort

E. Fluoxetine is an inhibitor of CYP450 enzymes. CYP1A2 is inhibited by fluvoxamine and duloxetine, and induced by phenytoin. CYP2D6 is inhibited by fluoxetine, paroxetine, sertraline, and duloxetine. CYP3A4 is inhibited by fluoxetine, nefazodone, and sertraline and is induced by carbamazepine, phenobarbital, and phenytoin. CYP2C9/10/19 is inhibited by fluvoxamine, fluoxetine, moclobemide, sertraline, and minimally by venlafaxine. St John’s wort induces CYP3A4. CYP3A4 metabolizes carbamazepine, oral contraceptives, atypical antipsychotics, Z hypnotics, benzodiazepines, and calcium channel blockers.

Reference:

1. Taylor et al., eds. The Maudsley Prescribing Guidelines, 8th edn. Taylor and Francis, 2005, p. 180.

Question 14#

Which of the following statements about first-order kinetics is false?

A. A fraction of the drug is eliminated per unit time

D. In first order kinetics, a constant fraction of the drug in the body is eliminated per unit time. The rate of elimination is proportional to the amount of drug in the body. The majority of psychiatric drugs are eliminated in this way. Volume of distribution is the amount of drug in the body divided by the concentration in the blood. So a drug that is highly lipid soluble and redistributes into fat has a high volume of distribution (Vd). These drugs stay out of the blood most of the time and, as a result, will have a long half-life. The lesser the clearance of the drug, the longer the half-life; so half-life is inversely proportional to the clearance. Digoxin is highly lipid soluble and has a long half-life.

Reference:

1. Gelder MG et al., eds. New Oxford Textbook of Psychiatry. Oxford University Press, 2000, p. 1287.

Question 15#

Which of the following is a butyrophenone?

A. Risperidone

C. Risperidone is a benzisoxazole; quetiapine is a dibenzothiazepine; clozapine and is a dibenzodiazepines; olanzapine is a thienobenzodiazepine; sulpiride and amisulpiride are substituted benzamides; chlorpromazine is a phenothazine; and haloperidol is a butyrophenone.

Reference:

1. Johnstone EC et al., eds. Companion to Psychiatric Studies, 7th edn. Churchill Livingstone, 2004, p. 259.