Correct Answer c chlorothiazide D

Explanation

1%=1000mg in a 100ml solution is the a starting point.

Therefore 1ml=10mg. 

Therefore 2ml=20mg

Therefore 10ml=100mg

Question 207

Regarding efficacy, which of the follwing statements is correct?

• 
  A It can be measured with a quantal dose response curve
  
• 
  B Partial agonists have higher maximal efficacy than full agonists
  
• 
  C It is the maximum effect a drug can bring about regardless of dose Correct Answer
  
• 
  D It is the drugs ability to produce 50% of its maximal effect
  

Explanation

Efficacy is measured by a graded dose response curve and not a quantal dose response curve. By definition partial agonists have a lower efficacy than full agonists

Question 208

Regarding t1/2, which of the following statements is true?
Your answer was not correct

• 
  A It can be poor predictor of clearance Correct Answer
  
• 
  B Is not affected by age
  
• 
  C Is not related to Vd
  
• 
  D Is related to volume of distribution and protein binding Your Answer
  

Explanation

T1/2 = 0.7 x VD/CL. There is a relation to the Vd. Disease states can affect T1/2. Renal impairment, which occurs in 2/3 of the elderly, will lengthen the half-life of most drugs. There is no relation to protein binding

Question 209

Which of the following is an example of a phase II biotransformation?
Your answer was not correct

• 
  A Oxidation Your Answer
  
• 
  B Reduction
  
• 
  C Methylation Correct Answer
  
• 
  D Hydrolysis
  

Explanation

Phase one reactions are hydration, oxidation and reduction. Phase two reactions are glucuronidation, acetylation, glutathione conjugation, glycine conjugation, sulfate conjugation, methylation, and water conjugation

Question 210

With regard to properties of a drug, which of the following statements is correct?
Your answer was correct

• 
  A Efficacy is the maximum response produced by a drug Correct Answer
  
• 
  B Spare receptors are present if Kd 50 is the same as EC 50.
  
• 
  C Potency is the same as affinity.
  
• 
  D TD50 is the concentration of a drug necessary to produce toxic effects 50 % of the time
  

Explanation

Spare receptors are present if the EC50

Potency: how much of a drug that is required to produce an effect.

Affinity: how tight the drug binds to its receptors.

TD50 is the dose required to produce toxic effects in 50% of patients.

Question 211

Which of the following statements regarding Naloxone is false?
Your answer was not correct

• 
  A Intravenous administration reverses opioid effects in 1-2min
  
• 
  B Naloxone has equal affinity for mu, kappa and delta receptors Correct Answer
  
• 
  C Naloxone is a pure antagonist
  
• 
  D Tolerance to naloxone does not develop Your Answer
  

Explanation

Naloxone is a pure antagonist. It has a very high affinity for mu receptors and a lower affinity for the other receptor binding sites.  Naloxone has a half life of 1-2 hours when given by injection and 10 hours when taking via the oral route.  Although naloxone is well absorbed via the oral route it undergoes rapid first pass metabolism. IVI administration reverses opioid toxicity in 1-3 minutes. There is no tolerance to the antagonistic action of these agnets, nor does withdrawal of naloxone after chronic administration precipitate an abstinence syndrome

Question 212

Which of the following is an example of Type 1 biotransformation reactions?
Your answer was not correct

• 
  A Methylation Your Answer
  
• 
  B Acetylation
  
• 
  C Hydrolysis Correct Answer
  
• 
  D Glucuronidation
  

Explanation

Phase one reactions are hydration, oxidation and reduction. Phase two reactions are glucuronidation, acetylation, glutathione conjugation, glycine conjugation, sulfate conjugation, methylation, and water conjugation

Which of the following statements regarding the bioavailability of a drug is correct?

• 
  A Must be 100% if given by inhalation.
  
• 
  B Is high if the drug is hydrophilic.
  
• 
  C Is equal to 1 (the extraction ratio)
  
• 
  D Is 70% for orally administered Digoxin. Correct Answer
  

Explanation

Inhalation gives a bioavailability of 5 to <100%. Hydrophilic and lipophilic drugs can have low rates of bioavailability. Too lipophilic, the drug will not be soluble enough to cross the water layer adjacent to the cell. The bioavailability of the drug (F) can be predicted from the extent of absorption (f) and the extraction ration (ER). F=f x (1-ER). 10% bioavailability is only via intravenous administration

What is the half life of Lignocaine?

• 
  A 10 minutes
  
• 
  B 30 minutes Your Answer
  
• 
  C 60 minutes
  
• 
  D 120 minutes Correct Answer
  

Explanation

Lignocaine has a t1/2 of 1-2 hours

Question 215

Calculate the half life of Digoxin in a 70 kg patient with a renal clearance of 8.4L/min and volume distribution of 5 L/Kg
Your answer was not correct

• 
  A 14 hours
  
• 
  B 29 hours Correct Answer
  
• 
  C 36 hours Your Answer
  
• 
  D 44 hours
  

Explanation

T1/2 = 0.7 x (VD/CL)

Question 216

Which of the following statements is correct?

The volume of distribution...

• 
  A Is proportional to half life. Correct Answer
  
• 
  B Is calculated by dividing the amount of drug by it's clearance
  
• 
  C If high suggests homogeneous distribution throughout tissues Your Answer
  
• 
  D If low suggests homogeneous distribution throughout tissues
  

Explanation

 Vd is an apparent volume.

The volume of distribution= amount of drug in the body/ concentration of the drug in blood or plasma.

Drugs with a high VD have higher extravascular concentrations than intravascular and are not homogenously distributed.

T1/2 = 0.7 x (VD / CL)

Question 217

How many mg in 2ml of a 0.5% weight per volume solution?

• 
  A 10mg Correct Answer
  
• 
  B 1 mg
  
• 
  C 100mg
  
• 
  D 5mg
  

Explanation

1%=1000mg in a 100ml solution is the a starting point.

Therefore 1ml=5mg. 

Therefore 2ml=10mg

Question 218

Which of the following is an example of a phase I reaction?
Your answer was correct

• 
  A Sulphation
  
• 
  B Glucuronidation
  
• 
  C Hydration Correct Answer
  
• 
  D Acetylation
  

Explanation

Phase one reactions are hydration, oxidation and reduction.

Phase two reactions are glucuronidation, acetylation, glutathione conjugation, glycine conjugation, sulfate conjugation, methylation, and water conjugation

Question 219

Calculate a Phenytoin loading dose for a 70 kg male; Target concentration 10 mg/L, Vd 0.5 L/kg

• 
  A 350 mg Correct Answer
  
• 
  B 300 mg
  
• 
  C 400 mg
  
• 
  D 3500 mg
  

Explanation

The LD = VD (l/kg) x TC. Therefore 0.5 x 70 =35L.

Question 220

Regarding irreversible antagonists, which of the following statements is correct?
Your answer was correct

• 
  A Require regeneration of receptors for further agonist action Correct Answer
  
• 
  B Can be displaced by increasing concentration of agonist
  
• 
  C Can be displaced by increasing potency of agonist
  
• 
  D Can be displaced by increasing efficacy of agonist
  

Explanation

Competitive antagonists can be overcome by sufficiently high concentration of agonists. Irreversible antagonists cannot. Consequently, the duration of action of such an irreversible antagonists relatively independent of its own rate of elimination and more dependent upon the rate of turnover of receptor molecules

Question 221

Which of the following drugs has a half-life of 6 hours?
Your answer was correct

• 
  A Diazepam
  
• 
  B Aspirin
  
• 
  C Digoxin
  
• 
  D Atenolol Correct Answer
  

Explanation

Aspirin's half life in 3-5hrs (first order kinetics) and 15hrs (zero order kinetics).

Digoxin’s half life is 40 hrs

Diazepam’s is 20-40hrs

Question 222

Which volatile anaesthetic is the least metabolized?
Your answer was correct

• 
  A Desflurane Correct Answer
  
• 
  B Sevoflurane
  
• 
  C Halothane
  
• 
  D Isoflurane
  

Explanation

The extent of hepatic metabolism, the order (most to least) of inhaled anaesthetic are methoxyflurane, halothane, enflurane, sevoflurane, isoflurane, desflurane, nitrous oxide. Nitrous oxide undergoes zero metabolism.

Question 223

Which of the following is an amide local anaesthetic agent?

• 
  A Benzocaine Your Answer
  
• 
  B Tetracaine
  
• 
  C Cocaine
  
• 
  D Prilocaine Correct Answer
  

Explanation

All the rest are Ester type local anaesthetics. Examples of Amide local anaesthetics are: lignociane, mepivacaine, bupivacaine, etidocaine and ropivacaine

Question 224

In pseudo (plasma) cholinesterase deficiency which of these two drugs will have a prolonged effect?

• 
  A Succinylcholine and Esmolol Your Answer
  
• 
  B Remifentanil and Esmolol
  
• 
  C Succinylcholine and Procaine Correct Answer
  
• 
  D Mivacurium and Esmolol
  

Explanation

Pseudocholinesterase deficiency will result in a prolonged effect of the following: succinylcholine, mivacurium, procaine, and cocaine. Iatrogenic causes of lower plasma pseudocholinesterase activity include medications such as the following:

• 
  Anticholinesterase inhibitors
  
• 
  Bambuterol
  
• 
  Chlorpromazine
  
• 
  Contraceptives
  
• 
  Cyclophosphamide
  
• 
  Echothiophate eye drops
  
• 
  Esmolol
  
• 
  Glucocorticoids
  
• 
  Hexafluorenium
  
• 
  Metoclopramide
  
• 
  Monoamine oxidase inhibitors
  
• 
  Pancuronium
  
• 
  Phenelzine
  

Question 225

Prolonged duration of neuromuscular blockade is seen following a vecuronium infusion.  Which of the following is the possible cause?

• 
  A Acidosis Your Answer
  
• 
  B Hypothermia Correct Answer
  
• 
  C Hyperkalaemia
  
• 
  D Long term steroid use
  

Explanation

In rare cases, long-term use of neuromuscular blocking drugs to fascilitate mechanical ventilation in ICU settings may be associated with prolonged paralysis and/or skeletal muscle weakness.  Patients may have received other drugs such as broad spectrum antibiotics, narcotics and steroids and may have severe diseases which lead to electrolyte imbalances, hypoxic episodes of varying duration, acid-base imbalance, hyperthermia and extreme debilitation any of which may enhance the actions of a neuromuscular blocking agent. 

Hypothermia (25 to 28°C) has been associated with a decreased requirement for nondepolarizing neuromuscular blocking agents.

Question 226

Which of these drugs can be used to treat central anticholinergic syndrome?

 
Your answer was not correct

• 
  A Physostigmine Correct Answer
  
• 
  B Benztropine Your Answer
  
• 
  C Pyridostigmine
  
• 
  D Atropine
  

Explanation

Physositgmine is the only carbamate that is well absorbed form all sites (lungs, skin, eye, gut) and is distributed into the central nervous system. 

Question 227

Which of the following opioids have INACTIVE metabolites? 

 
Your answer was not correct

• 
  A Oxycodone Your Answer
  
• 
  B Morphine
  
• 
  C Methadone Correct Answer
  
• 
  D Codeine
  

Explanation

Morphine=hydromorphone.

Codeine= hydrocodone.

Oxycodone= oxymorphone.

Pethidine = norpethidine

Unlike codeine, morphine, hydromorphone, pethidine or oxycodone, methadone has no active metabolites and is therefore a good choice for patients at risk for toxicity from metabolite accumulation

Question 228

With the MAOI tranylcypromine, which drug will be least problematic?

• 
  A Propofol Correct Answer
  
• 
  B Pethidine
  
• 
  C Ephedrine Your Answer
  
• 
  D Phenylephrine
  

Explanation

Tranylcypromine is a MAOI, which will inhibit the catabolism of dietary amines. When foods containing tyramine are ingested, the patient may develop a hypertensive crisis. The mechanism is poorly understood but is thought that tyramine displaces noradrenaline from the storage vesicles. Therefore all drugs with sympathommimetic properties will be problematic when associated with MAOIs. Pethidine is associated with serotonin syndrome when given with the MAOI drug group

Question 229

Which drug does NOT have antiemetic properties when used as an?

• 
  A Ketamine Correct Answer
  
• 
  B Ondansetron
  
• 
  C Midazolam
  
• 
  D Dexamethasone
  

Explanation

Ketamine does not have antiemetic properties but is often used with propofol=Ketofol, as Propofol has antiemetic effects. The antiemetic effect is stated in Katzung, but there is some controversy as to whether it really does. See below.

In a study reported in the clinical journal of anaesthetics it stated that many anaesthesiologists used propofol for its antiemetic effect. There is strong evidence for its antiemetic efficacy after anaesthesia maintained by a propofol infusion and also for its use in the post anaesthetic patient. However, there is little evidence to support its use purely at induction of anaesthesia or using it at the beginning or end of a case in an attempt to reduce postoperative nausea and vomiting. This is especially true in cases lasting longer than a few minutes

Question 230

Which of the following inhaled gases are metabolised greater than 10%?

 
Your answer was not correct

• 
  A Isoflurane Your Answer
  
• 
  B Sevoflurane
  
• 
  C Halothane Correct Answer
  
• 
  D Nitrous oxide
  

Explanation

Metabolism of inhaled anaesthetics:

Nitrous oxide 0%.

Sevoflurane 2-5%.

Isoflurane- <2%.

Halothane >40%.

Enflurane-8%. 

Question 231

Which of the following is most likely to cause raised intracranial pressure?

• 
  A Ketamine Correct Answer
  
• 
  B Propofol
  
• 
  C Thiopentone
  
• 
  D Nitrous oxide
  

Explanation

Ketamine markedly increases cerebral blood flow, cerebral oxygen consumption and intracranial pressure. Inhaled anaesthetics decrease the metabolic rate of the brain but do increase cerebral blood flow. Nitrous oxide increases cerebral blood flow the least. Thiopentone decreases cerebral metabolism, oxygen consumption and cerebral blood flow. Propofol reduces cerebral blood flow and cerebral metabolism

Question 232

The following cause an increase in intra-abdominal pressure?

• 
  A Neostigmine
  
• 
  B Suxamethonium Correct Answer
  
• 
  C Morphine
  
• 
  D Metoclopramide Your Answer
  

Explanation

In some patients especially muscular ones, the fasiculations associated with suxamethonium will cause a rise in intra gastric pressure from 5-40cmH20. The result of which may cause vomiting and aspiration. This effect is not seen with the non depolarising muscle relaxants

Question 233

The following increase intra-ocular pressure?
Your answer was not correct

• 
  A Hypoventilation
  
• 
  B Ketamine
  
• 
  C Suxamethonium Correct Answer
  
• 
  D Halothane Your Answer
  

Explanation

Intraocular pressure increases following administration of suxamethonium. It occurs 1 min after injection, is maximal at 2-4 min and starts to subside after 5min. The mechanism may involve contractions of tonic myofibrils or transient dilation of chorodial blood vessels. Despite this increase, the use of suxamethonium is not contraindicated unless the anterior chamber is to be opened.

Question 234

Thiopentone is a “short-lasting” barbiturate because?

• 
  A It is administrated by IV injection
  
• 
  B It is bound to the “sleep centre” in the brain
  
• 
  C It is rapidly distributed throughout the body Correct Answer
  
• 
  D It is metabolised rapidly by brain and liver
  

Explanation

It is “short lasting” because of the rapid removal form brain tissue into the other highly vascularised tissues and is redistributed to muscle, fat and eventually all body tissues. It is only metabolised at a rate of 12-16% following a single dose. It facilitates the action of GABA and increase the opening of the Cl channels.

Question 235

Which of the following may be administered via the tracheal mucosa?

• 
  A Calcium chloride
  
• 
  B Suxamethonium
  
• 
  C Lignocaine Correct Answer
  
• 
  D Theophylline Your Answer
  

Explanation