Your answer was not correct

• 
  A Felodopine Your Answer
  
• 
  B Verapamil
  
• 
  C Nifedipine Correct Answer
  
• 
  D Diltiazem
  

Explanation

Diltiazem-oral onset of action >30m. Nifedipine-oral onset of action 5-20m. Verapimil-oral onset of action is 30m. Felodipine oral onset of action  is 2-5hrs

Question 175

Which of the following statements regarding verapamil is correct?
Your answer was correct

• 
  A It is a positive inotrope
  
• 
  B It inhibits activated and inactivated sodium channels
  
• 
  C It is a dihydropyridone
  
• 
  D It is an example of a class IV antiarrhythmic Correct Answer
  

Explanation

Verapamil is a negative inotropic drug (calcium channel blocker). It slows conduction through the SA and the AV nodes. Blockade of the calcium channel results in a decrease in cardiac contractility, a decrease in the sinus node pacemaker rate, and AV node conduction velocity. It blocks L type voltage gated calcium channels. It is not part of the dihydropyridine group

Question 176

Which of the following drugs does not prolong the refractory period of normal cells?
Your answer was correct

• 
  A Amiodorone
  
• 
  B Lignocaine Correct Answer
  
• 
  C Quinidine
  
• 
  D Sotalol
  

Explanation

Amiodarone class 1A III, prolongs AP/QRS and ERP. Sotalol class III-prolongs QT and ERP.

Quinidine class 1A Prolongs AP/QRS but also prolongs ERP/QT. Lignocaine class 1B- only effects ischaemic tissue and shortens the ERP. Procainamide class 1A prolongs AP/QRS and prolongs ERP/QT. Remember that class 1C prolongs the AP but has no effect on the QT/ERP

Question 177

Which of the following statements regarding adenosine is correct?

• 
  A Its receptors are ion channels
  
• 
  B It increases AV nodal conduction
  
• 
  C It enhances potassium conductance Correct Answer
  
• 
  D It has a half life of 2 minutes
  

Explanation

Adenosine binds to a G protein receptor and activated CAMP. Its mechanism of action involves enhanced potassium conductance and inhibition of CAMP induced calcium influx. The result of these actions are marked hyperpolarization and suppression of calcium dependent action potentials. It is the drug of choice for the termination of supraventricular tachycardia as it directly inhibits AV nodal conduction and increases the AV node refractory period. It has less effect on the SA node. Half-life <10s. It is less effective in the presence of adenosine receptor blockers such as theophylline, caffeine and increased by adenosine uptake inhibitors such as dipyridamole

Question 178

All of the following drugs may increase the effect of digoxin except?
Your answer was correct

• 
  A Verapamil
  
• 
  B Amiodorone
  
• 
  C Frusemide
  
• 
  D Carbamazepine Correct Answer
  

Explanation

Other drugs which potentiate digoxin effect include: quinidine, NSAIDs, calcium channel blocker- (not in humans though). Antibiotics that alter gut flora may increase bioavailability, and catecholamines may sensitize the myocardium to digitalis induced arrhythmias.

Verapamil and amiodarone reduce digoxin clearance.

Regarding dgoxin, which of the following answers is correct?

• 
  A It is a negative inotrope Your Answer
  
• 
  B It has atropine like effects on heart acetylcholine receptors
  
• 
  C It inhibits central vagal effects
  
• 
  D It increases ventricular excitability Correct Answer
  

Explanation

Digoxin is a positive inotrope. It increases ventricular excitability, which increases contraction, ventricular ejection, and cardiac output. The increased output eliminates the stimuli evoking increased sympathetic outflow; both heart rate and vascular tone diminish. With decreased end diastolic fiber tension (the result of increased systolic ejection and decreased filling pressure), heart size and oxygen demand decreases. Finally, increased renal blood flow improves glomerular filtration and reduces aldosterone driven sodium reabsorption. It has cardioselective parasympathomimetic effects. Cardiac glycosides inhibit the Na/K ATPase pump. Low K and MG and a high CA potentiate digitalis

Question 180

In normal cells, which of the following drugs shortens the refractory period?
Your answer was not correct

• 
  A Amiodarone
  
• 
  B Quinidine Your Answer
  
• 
  C Lignocaine Correct Answer
  
• 
  D Procainamide
  

Explanation

Amiodarone class 1A III, prolongs AP/QRS and ERP. Sotalol class III-prolongs QT and ERP.

Quinidine class 1A Prolongs AP/QRS but also prolongs ERP/QT.

Lignocaine class 1B- only effects ischaemic tissue and shortens the ERP.

Procainamide class 1A prolongs AP/QRS and prolongs ERP/QT.

Remember that class 1C prolongs the AP but has no effect on the QT/ERP

Question 181

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

• 
  A Leukopenia is a common side effect Your Answer
  
• 
  B It reduces platelet aggregation by the irreversible inhibition of the ADP-receptor Correct Answer
  
• 
  C It has no GI side effects
  
• 
  D It inhibits prostaglandin metabolism
  

Explanation

Ticlopidine, unlike aspirin, has no effect on prostaglandin metabolism.

GIT symptoms do occur: 20% may suffer dyspepsia, nausea and diarrhea. 5% GIT haemorrhage.

Only 1% of patients develop leucopenia. TTP may also occur.

Question 182

In which condition is Low molecular weight heparin levels in plasma not necessary to measure?
Your answer was not correct

• 
  A Obesity Your Answer
  
• 
  B Liver insufficiency Correct Answer
  
• 
  C Renal insufficiency
  
• 
  D Pregnancy
  

Explanation

Weight based dosing of LMWH results in predictable pharmakokinetics and plasma levels in patients with normal renal function. Therefore, LMWH levels are not generally measured except in the setting or renal insufficiency, obesity (body wt >150kg) and pregnancy

Question 183

Which of the following drugs does not increase the action of warfarin?
Your answer was correct

• 
  A Metronidazole
  
• 
  B Amiodarone
  
• 
  C Disulfiram
  
• 
  D Phenobarbitone Correct Answer
  

Explanation

Drugs that decrease INR (increase metabolism): vitamin k, diuretics, barbiturates, rifampicin, cholestyramine

Drugs that increase INR (decrease metabolism): phenylbutazone, metronidazole, miconazole, trimethoprim, sulphamethoxazole, sulfinpyrazone, disulfram, cimetadine, amiodarone and cephalosporin’s

Regarding warfarin, which of the following statements is correct?

• 
  A It is broken down in the GIT
  
• 
  B It has a half life of 6 hours
  
• 
  C It decreases thromboplastins Correct Answer
  
• 
  D It is 75% protein bound Your Answer
  

Explanation

Warfarin has a bioavailability of 100%. Over 99% of warfarin is bound to plasma albumin, which may contribute to its small volume of distribution, its long half-life of 36hrs and it lack of urinary excretion of unchanged drug. The traditional term “thromboplastin” refers to a phospholipid-protein extract of tissue (usually lung, brain, or placenta) that contains both the tissue factor and phospholipid necessary to promote activation of factor X by factor VII. Warfarin’s anticoagulant effect results from a balance between partially inhibited synthesis and unaltered degradation of the four vitamin K dependant clotting factors- 2, 7, 9, 10

Question 185

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

• 
  A LMW fractions have more effect on thrombin than HMW fractions
  
• 
  B It may cause alopecia Correct Answer
  
• 
  C It inhibits antithrombin III
  
• 
  D Protamine is a competitive antagonist of heparin
  

Explanation

LMW heparin inhibits activated factor X but has less effect on antithrombin - and on the coagulation in general - than HMW heparin. Heparin’s biological activity is dependant upon the plasma potease inhibitor antithrombin III. In the presence of heparin the antithrombin-clotting factor complex (which inhibits clot formation) is accelerated 1000 fold. Heparin accelerates  this antithrombin protease inhibitory reaction against clotting factors IIa, IXa, and Xa by forming equimolar stable complexes with them Protamin binds to heparin and forms a complexes devoid of anticoagulant activity

Question 186

Heparin induced mild thrombocytopenia is caused by?
Your answer was not correct

• 
  A Release of lipoprotein lipase Your Answer
  
• 
  B Platelet aggregation. Correct Answer
  
• 
  C Thrombosis
  
• 
  D Anti-platelet antibodies
  

Explanation

Heparin induced thrombocytopenia is transient and occurs within the first 5 days. A smaller subset of patients may develop an antibody-mediated cause of thrombocytopenia that is associated with thrombosis. In this instance, the heparin-induced antibody is directed against the heparin platelet factor 4 complex. These antigen-antibody complexes bind to the Fc receptor on adjacent platelets, causing aggregation and paradoxical thromboembolism

Question 187

Which of the following statements regarding streptokinase is true?
Your answer was not correct

• 
  A It activates the plasminogen that is bound to fibrin
  
• 
  B It is a complex lipopolysaccharide. Your Answer
  
• 
  C It is synthesised by the human kidney
  
• 
  D It binds to the endogenous plasminogen Correct Answer
  

Explanation

Streptokinase is a protein (but not an enzyme in itself) synthesized by streptococci. It combines with the proactivator plasminogen.

The kidney synthesizes urokinase.

tPA peferentially activate plasminogen that is bound to fibrin

Question 188

Which statment is not true of warfarin?
Your answer was not correct

• 
  A It has 100% bioavailability Your Answer
  
• 
  B It is 99% protein bound
  
• 
  C It affects vitamin K synthesis
  
• 
  D Half life is 6 hours Correct Answer
  

Explanation

Warfarin’s half-life is 36hrs.

Question 189

If a patient is on warfarin, which of the following drugs cause an increased INR?
Your answer was not correct

• 
  A Cholestyramine
  
• 
  B Amiodorone Correct Answer
  
• 
  C Rifampicin Your Answer
  
• 
  D Barbituates
  

Explanation

Drugs that decrease INR (increase metabolism): vitamin k, diuretics, barbiturates, rifampicin, cholestyramine

Drugs that increase INR (decrease metabolism): phenylbutazone, metronidazole, miconazole, trimethoprim, sulphamethoxazole, sulfinpyrazone, disulfram, cimetadine, amiodarone and cephalosporin’s

Regarding fibrinolytics, select the correct answer.

• 
  A tPA does not occur naturally
  
• 
  B All thrombolytics act to convert free plasminogen to plasmin.
  
• 
  C Urokinase is a human product Correct Answer
  
• 
  D APSAC lack the streptococcal antigen
  

Explanation

Fibrinolytics act by converting plasminogen to plasmin. Urokinase is a human enzyme synthesized by the kidney. APSAC- anisoylated plasminogen streptokinase activator complex- consists of a complex of purified human plasminogen and bacterial streptokinase that has been acylated to protect the enzyme’s active site. tPA occurs on the endothelial cells of vessels

Question 191

Which statement is correct regarding fibrinolytics?
Your answer was not correct

• 
  A Streptokinase is a human product
  
• 
  B Aminocaproic acid is an inhibitor of fibrinolysis Correct Answer
  
• 
  C Gastrointestinal bleed within the previous 12 months is a contraindication Your Answer
  
• 
  D TIMI trial shows that GI haemorrhage is the most common adverse effect
  

Explanation

Streptokinase is a streptococcal bacterial protein.

A GIT bleed in the last 2-4 weeks or an active peptic ulcer is a contraindication to fibrinolysis.

TIMI trial showed that haemorrhagic stroke is the most common side effect.

Urokinase is a cheap human enzyme.

Question 192

Which if the following clotting factor proteases does Heparin not inhibit

• 
  A Va Correct Answer
  
• 
  B IIa Your Answer
  
• 
  C IXa
  
• 
  D Xa
  

Explanation

Heparin is a heterogenous mixture of sulphated mucopolysaccarides extracted from porcine or bovine intestine. It is used in the first and third trimester of pregnant when indicated. Warfarin is used in the second trimester. It must be given IV or in the cleaxane form, subcutaneously. Protamine sulphate neutralizes heparin directly. Heparin is of animal origin and should be used with caution in patients with allergy. Increased loss of hair and transient alopecia has been reported. Long term heparin is associated with osteoporosis and spontaneous fractures. Mineral corticoid deficiency is also associated with long term heparin usage. Heparin accelerates antithrombin protease inhibitory reaction against clotting factors IIa, IXa, and Xa by forming equimolar stable complexes with them

Question 193

Which of the following drugs does not interact with warfarin?
Your answer was not correct

• 
  A Cephalosporins
  
• 
  B Phenobarbitone
  
• 
  C Loop diuretics Your Answer
  
• 
  D Benzodiazepines Correct Answer
  

Explanation

Drugs that decrease INR (increase metabolism): vitamin k, diuretics, barbiturates, rifampicin, cholestyramine

Drugs that increase INR (decrease metabolism): phenylbutazone, metronidazole, miconazole, trimetoprim, sulphamethoxazole, sulfinpyrazone, disulfram, cimetadine, amiodarone and cephalosporin’s

Question 194

What drug does not affect  the metabolism of warfarin?

• 
  A Phenobarbiton
  
• 
  B Rifampicin
  
• 
  C Cimetidine
  
• 
  D Benzodiazepines Correct Answer
  

Explanation

Drugs that decrease INR (increase metabolism): vitamin k, diuretics, barbiturates, rifampicin, cholestyramine. Hypothyroidism also increases metabolism.

Drugs that increase INR (decrease metabolism): phenylbutazone, metronidazole, miconazole, trimetoprim, sulphamethoxazole, sulfinpyrazone, disulfram, cimetadine, amiodarone and cephalosporin’s

How does Cromolyn reduce bronchial reactivity?

• 
  A Relaxing smooth muscle cells
  
• 
  B Inhibiting eosinophil chemotactic factor
  
• 
  C Direct bronchodilation
  
• 
  D Inhibiting mediated mast cell degranulation. Correct Answer
  

Explanation

Cromolyn does not inhibit the IGE interaction with the agonist or the mast cell but rather once the complex is formed it prevents the degranulation of the mast cell

Question 195

How does Cromolyn reduce bronchial reactivity?
Your answer was correct

• 
  A Relaxing smooth muscle cells
  
• 
  B Inhibiting eosinophil chemotactic factor
  
• 
  C Direct bronchodilation
  
• 
  D Inhibiting mediated mast cell degranulation. Correct Answer
  

Explanation

Cromolyn does not inhibit the IGE interaction with the agonist or the mast cell but rather once the complex is formed it prevents the degranulation of the mast cell

Question 196

Regarding Ipratropium, which of the following statements is correct?
Your answer was not correct

• 
  A Causes miosis
  
• 
  B Inhibits mast cells Your Answer
  
• 
  C Readily enters the CNS
  
• 
  D It has an onset 1-3mins after administration Correct Answer
  

Explanation

Ipratropiums onset of action is 1-3 min and has a duration of action of 4-6hrs. It blocks acetylcholine causing bronchodilitation. It does not cause miosis nor does it enter the CNS

Question 197

Salbutamol may cause all the following except
Your answer was correct

• 
  A Hyperkalemia Correct Answer
  
• 
  B Decreased PO2 initially
  
• 
  C Skeletal muscle tremor
  
• 
  D Weakness
  

Explanation

Salbutamol is used in the acute treatment of hyperkalemia. In children, following large a amount, salbutamol can produce severe vomiting.

Question 198

All of the following drugs cause DIRECT bronchodilation EXCEPT
Your answer was correct

• 
  A Disodium cromoglycate Correct Answer
  
• 
  B Theophylline
  
• 
  C Adrenaline
  
• 
  D Atropine
  

Explanation

Disodium cromoglycate are only of value when taken prophylactically. When used as aerosols they inhibit both antigen and exercise induced asthma. Chronic usage slightly reduces the overall level of bronchial reactivity. These drugs however, have no effect on airway smooth muscle tone and are ineffective in reversing asthmatic bronchospams

Question 199

Which is an effect of methylxanthines?
Your answer was not correct

• 
  A Stimulation of cell surface adenosine receptors Your Answer
  
• 
  B Negative inotropic effect
  
• 
  C Increased strength of muscle contraction Correct Answer
  
• 
  D Weak anti-diuresis
  

Explanation

The methyxanthines have effects on the CNS, kidney, CVS, GIT and skeletal and smooth muscle. The therapeutic effect is not just confined to the airways (bronchodilitation), they also strengthen the contractions of isolated skeletal muscles and have potent effects in improving contractility and reducing fatigue of the diaphragm in patients with COPD. They cause mild cortical arousal with increased alertness and deferral of fatigue. They cause both positive inotropic and chronotropic effects on the heart. They are weak diuretics. They inhibit surface cell adenosine receptors- these receptors cause smooth muscle airway contraction and promote histamine release.

Question 200

The Beta 2 sympathomimetic with the longest duration of action is?
Your answer was not correct

• 
  A Isoprotenerol Your Answer
  
• 
  B Salmeterol Correct Answer
  
• 
  C Sotalol
  
• 
  D Terbutaline
  

Explanation

Femoterol is also a long acting agonist

Question 201

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

• 
  A It is a positive chronotrope and inotrope Correct Answer
  
• 
  B It reduces GFR Your Answer
  
• 
  C It is thought to increase blood viscosity
  
• 
  D It has a Vd of 10L/kg
  

Explanation

Theophylline increases GFR and is thought to decrease blood viscosity. It is the most potent drug for bronchodilitation. VD= 0.3-0.7L/Kg

Question 202

Regarding theophylline, which of the following is not an overdose effect?
Your answer was not correct

• 
  A Seizures
  
• 
  B Hypokalaemia Your Answer
  
• 
  C Hypocalcaemia Correct Answer
  
• 
  D Tachycardia
  

Explanation

Theophylline toxicity also produces hypoMg and HypoPO4

Question 203

Which of the following drugs does not possess bronchodilator activity?
Your answer was not correct

• 
  A Atropine
  
• 
  B Sodium cromoglycate Correct Answer
  
• 
  C Theophylline
  
• 
  D Adrenaline Your Answer
  

Explanation

Sodium Cromoglycate has no effect on bronchial smooth muscle tone. It is ineffective in reversing asthmatic bronchospasm. It is used for the prophylactic treatment of exercise and allergen induced asthma. It inhibits cell activation by alteration in function of cell membrane chloride channels. It prevent mast cell degranulation.

Question 204

Regarding pharmacokinetics, which of the following statements is true?
Your answer was correct

• 
  A Efficacy is measured by gram-for-gram effect
  
• 
  B Potency is maximal drug effect.
  
• 
  C Potency is dose of maximal effect.
  
• 
  D Efficacy is the maximal effect of a drug Correct Answer
  

Explanation

Potency is the dose required to bring about 50% of the drug’s maximal effect. Efficacy is only measured by a graded dose response curve and not by a quantal dose response curve

Question 205

Regarding therapeutic index, which of the following statements is correct?
Your answer was not correct

• 
  A It is the ratio of ED50/LD50 Your Answer
  
• 
  B It is the ratio of TD50/ED50 Correct Answer
  
• 
  C High therapeutic index means a drug is dangerous
  
• 
  D Potent drugs are more likely to have a high therapeutic index.
  

Explanation

Therapeutic index is relationship of the dose of a drug required to produce a desired effect to that which produces an undesirable effect. Drugs with a high TI are safer. Potency of drugs has no relationship to the TI

Question 206

10 ml of 1% weight to volume is equal to:
Your answer was not correct

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