MCEM Pharmacology

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MCEM Pharmacology
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Core Content

• Need to have a detailed knowledge of the
  principles underlying the pharmacological
  management of conditions in the ED. In
  particular
• CNS Analgesics anaesthetics sedatives
• Respiratory Beta agonists anti-cholinergic
  agents
• Cardiac anti-arhythmics inotropes nitrates
• Infection antibiotics and antiviral agents
• GI antacids proton pump inhibitors anti
  spasmodics laxatives anti diarrhoeal
• Coagulation Heparin warfarin thrombolysis
  FFP protamine aspirin
• Anti inflamm. NSAID steroids
• Diabetes oral hypoglycaemic agents anti
  hyperglycaemic agents glucagon insulin
• Antidotes

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Question 1

• The following are true of drugs used in the
  treatment of ventricular arrhythmias
• Lignocaine toxicity is rare when used as an
  intravenous infusion as the half life is less
  than 20 minutes
• Amiodarone may cause clinical hyperthyroidism
• ß blockers increase automaticity by blocking the
  effects of endogenous catacholamines
• Lignocaine is a negative inotrope

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Q1. Answer - F T F T

• Lignocaine is a class Ib antiarrhythmic drug. It
  blocks the sodium channel. It depresses
  conduction of premature beats and conduction
  through ischaemic tissue. It shortens the action
  potential, although this is not associated with
  changes on the 12 lead ECG. . The half life is
  approximately 1.5 hours, although this is
  extended to up to 10 hours in severe cardiac
  failure or shock. Steady state following
  infusion is not achieved for 6 hours
  (approximately four elimination half lives). As
  such lignocaine toxicity is not uncommonly seen
  in association with intravenous infusions. The
  most common features associated with lignocaine
  toxicity are neurological, but lignocaine also
  has negatively inotropic effects and may cause AV
  block.
• ß blockers reduce automaticity of the SA and AV
  nodes by competitively inhibiting intrinsic
  catecholamine binding to ß adrenoreceptors.
• Amiodarone is a highly effective treatment for
  many ventricular and supraventricular
  arrhythmias. This efficacy is compromised by the
  wide range of side effects, including pulmonary
  infiltrates and fibrosis, corneal deposits,
  photosensitivity, neuropathy and hyper or
  hypothyroidism

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Question 2

• The following drugs may cause acute haemolytic
  anaemia
• Trimethoprim
• Nitrofurantoin
• Nalidixic acid
• Methicillin

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Q.2 Answer F T T T

• Common Antibiotic Causes of drug-induced
  haemolytic anaemias
• Penicillin / Ampicillin / Methicillin
• 2nd 3rd Generation Cephalosporins
• Nitrofurantoin

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Question 3

• Anticoagulation in patients taking warfarin may
  be affected by treatment with
• Ampicillin
• Ibuprofen
• Aspirin
• Morphine

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Q.3 Answer T T T F

• Something similar has been asked in past
• The interactions with NSAIDs and Aspirin are
  somewhat debatable but are considered to
  enhance.
• Most antibiotics will enhance effect
• Those NOT
• Trimethoprim / Tetracyclines
• Rifampicin REDUCES EFFECT

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Question 4

• Acute dystonic reactions may occur following oral
  admistration of
• Prochlorperazine
• Diazepam
• Metoclopramide
• Haloperidol

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Q.4 Answer T F T T

• Although dystonic reactions are occasionally dose
  related, these reactions are more often
  idiosyncratic and not predictable.
• They appear to result from drug-induced
  alteration of dopaminergic-cholinergic balance in
  the basal ganglia.
• Most drugs produce dystonic reactions by dopamine
  D2 receptor blockade, which leads to an excess of
  striatal cholinergic output.
• Agents that balance dopamine blockade with
  muscarinic M1 receptor blockade are less likely
  to produce a dystonic reaction.

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Question 5

• With respect to the clotting cascade
• Warfarins main action is on the Intrinsic
  pathway
• Warfarin affects production of Factors III,
  VII,IX, X
• Heparin affects thrombin and the Intrinsic
  pathway
• Prothrombin Complex Concentrate contains factors
  IX and X

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Q.5 Answer F F T T

• Warfarins main effects are on the extrinsic
  pathway and Vitamin K dependent factors II, VII,
  IX X
• Heparins main effects act via potentiation of
  Antithrombin III

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Question 5

• Regarding oral hypoglycemic agents
• Metformin is cleared by hepatic metabolism
• Metformin acts by stimulating insulin release
• Glipizide has its main effects by improving
  insulin sensitivity
• Glucophages are more likely to cause hypoglycemic
  episodes than sulphonylureas

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Q.5 Answers F F F F

• Glipizide (sulfonylurea) acts by stimulating
  insulin release and is cleared by hepatic
  hydroxylation can cause hypoglycemia
• Metformin (biguanide) reduces hepatic release,
  gut absorption of glucose and peripheral
  utilisation. It is cleared by renal excretion and
  does not cause hypoglycemia in isolation.

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Question 6

• The following drugs have their main direct
  effects at the receptors listed
• Adrenaline alpha-1, beta-12
• Noradrenaline alpha-1 beta-2
• Phenylephrine alpha-1 beta-1
• Dobutamine beta-12

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Q.6 Answers T F F F

• Adrenaline has effects on all alpha/beta
  receptors.
• Noradrenaline has effects on all but beta 2
• Dobutamine has its main effects on beta1
• Phenylephrine on alpha 1 receptors

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Question 7

• The following statements regarding local
  anaesthetics are correct
• They work by decreasing the resting action
  potential of nerve cells
• They work by blocking sodium channels
• The maximum dose of bupivacaine is 2mg/kg
• The initial signs of overdose is cardiac
  dysrhythmias

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Q.7 Answer F T T F

• Local anaesthetics act mainly on sodium channels,
  but do not effect the resting or threshold
  potential, they prolong the repolarisation phase.
• In overdose, neurological sequelae are noted
  first
• Maximum dose of common drugs

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• Suxamethonium is a non depolarising neuromuscular
  blocker
• The normal dose of suxamethonium is 10-20 mg/kg
• Suxamethonium is associated with bradycardia
• Ketamine is a bronchodilator
• Propofol is not associated with cardiovascular
  depression

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• Suxamethonium is a non depolarising neuromuscular
  blocker
• FALSE - is a depolarising blocker producing
  profound paralysis within 30-45 s
• The normal dose of suxamethonium is 10-20 mg/kg
• FALSE 1.5-2mg/kg
• Suxamethonium is associated with bradycardia
• TRUE esp in children who are sensitive to
  muscarinic effects of suxamethonium
• Ketamine is a bronchodilator
• TRUE
• Propofol is not associated with cardiovascular
  depression
• FALSE

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• The following anti-dotes and poisons are
  correctly paired
• Ethylene Glycol Ethanol/ Fomepizole
• B Blockers Glucagon/Atropine
• Cyanide Sodium Nitrite/Sodium thiosuphate/Dicobat
  e Edetate
• Methanol Ethanol/Folmepizole
• Organophosphates Fomepazole

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• The following anti-dotes and poisons are
  correctly paired
• Ethylene Glycol Ethanol/ Fomepizole
• TRUE
• B Blockers Glucagon/Atropine
• TRUE
• Cyanide Sodium Nitrite/Sodium thiosuphate/Dicobat
  e Edetate
• TRUE (also ?)
• Methanol Ethanol/Fomepazole
• TRUE
• Organophosphates Fomepazole