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Questions and Answers

What is the primary receptor that cardio-selective beta blockers bind to in cardiac tissue?

  • α1 receptor
  • β1 receptor (correct)
  • α2 receptor
  • β2 receptor

    • What is a potential risk factor for toxicity when taking beta blockers?

  • Young patients
  • Patients with hypertension
  • Patients with asthma
  • Patients with established ischemic heart disease (correct)

    • What is a common clinical feature of beta blocker toxicity?

  • Tachypnea
  • Hypertension
  • Bradycardia (correct)
  • Tachycardia

    • What is a characteristic of non-selective beta blockers?

    <p>Equal affinity for β1 and β2 receptors</p> Signup and view all the answers

    What is the term for the Na+ channel blocking effects of some beta blockers?

    <p>Quinidine-like effects</p> Signup and view all the answers

    What is the timeframe for the onset of toxicity with non-sustained release beta blockers?

    <p>Within 6 hours</p> Signup and view all the answers

    What is the timeframe for the onset of toxicity with sustained release beta blockers?

    <p>Within 8 hours</p> Signup and view all the answers

    What is a characteristic of some beta blockers, also known as 'intrinsic sympathomimetic activity'?

    <p>Partial agonist activity at adrenoceptors</p> Signup and view all the answers

    What is the therapeutic range of theophylline concentrations?

    <p>10-20 mg/L</p> Signup and view all the answers

    What is the suggested treatment for Theophylline-Related Agitation and Anxiety?

    <p>Benzodiazepines</p> Signup and view all the answers

    What complication can occur due to theophylline toxicity?

    <p>Rhabdomyolysis</p> Signup and view all the answers

    What is the purpose of measuring plasma theophylline concentrations?

    <p>To determine the severity of toxicity</p> Signup and view all the answers

    What is the reason to avoid haloperidol in treating Theophylline-Related Agitation and Anxiety?

    <p>It lowers seizure threshold</p> Signup and view all the answers

    Why should charcoal haemoperfusion be considered for patients with Theophylline toxicity?

    <p>It enhances theophylline clearance to a greater extent than haemodialysis</p> Signup and view all the answers

    What is the recommended interval for repeating measurements of plasma theophylline concentrations in severe poisoning?

    <p>Every 2-4 hours</p> Signup and view all the answers

    What is the alternative to charcoal haemoperfusion if it is not available?

    <p>Haemodialysis</p> Signup and view all the answers

    What is the apparent half-life of theophylline in cases of overdose?

    <p>20-30 hours</p> Signup and view all the answers

    What is a common cardiac effect of theophylline toxicity?

    <p>Sinus tachycardia</p> Signup and view all the answers

    What is the suggested dose of Diazepam for treating convulsions in adults?

    <p>10-20 mg</p> Signup and view all the answers

    Why should potassium replacement be done cautiously in Theophylline toxicity?

    <p>Because of normal total body potassium burden despite systemic hypokalaemia</p> Signup and view all the answers

    What is the purpose of the grading system for acute theophylline toxicity?

    <p>To determine the severity of toxicity</p> Signup and view all the answers

    What is the suggested dose of Lorazepam for treating convulsions in adults?

    <p>1-4 mg</p> Signup and view all the answers

    What is the initial management step in patients with acute theophylline toxicity?

    <p>Ensure a clear airway and adequate ventilation</p> Signup and view all the answers

    What is the case report that has been successful in enhancing theophylline elimination after overdose?

    <p>Continuous Veno-Venous Haemofiltration</p> Signup and view all the answers

    What type of agents are streptokinase and urokinase?

    <p>Non-specific agents</p> Signup and view all the answers

    What is the half-life of factor VII?

    <p>5 hours</p> Signup and view all the answers

    What is the purpose of monitoring prothrombin time?

    <p>To monitor the INR</p> Signup and view all the answers

    What is the effect of enzyme inhibitors of hepatic microsomal enzymes on bleeding risk?

    <p>Increases the risk of bleeding</p> Signup and view all the answers

    What is the impact of genetic variability on warfarin dosing?

    <p>It affects warfarin dosing variability between patients</p> Signup and view all the answers

    What is the difference in potency between S-warfarin and R-warfarin?

    <p>S-warfarin is 5 times more potent</p> Signup and view all the answers

    What is the half-life of racemic warfarin?

    <p>35 hours</p> Signup and view all the answers

    What is the reversal agent for warfarin?

    <p>Vitamin K</p> Signup and view all the answers

    What is the characteristic of long-acting anticoagulants?

    <p>They have a zero-order elimination, leading to a long duration of action</p> Signup and view all the answers

    What is the minimum dose of vitamin K to be given to a child?

    <p>250 micrograms/kg</p> Signup and view all the answers

    What is the management for warfarin excess in patients not normally on warfarin?

    <p>Monitor the INR to guide therapy</p> Signup and view all the answers

    Why should vitamin K be delayed after activated charcoal use?

    <p>Because charcoal absorbs vitamin K</p> Signup and view all the answers

    What is unfractionated heparin dosed in?

    <p>Units</p> Signup and view all the answers

    What is the effect of repeat dosing of unfractionated heparin?

    <p>Anticoagulant action increases</p> Signup and view all the answers

    What is the purpose of monitoring APTT?

    <p>To monitor the effect of heparin</p> Signup and view all the answers

    What is the difference between unfractionated heparin and low-molecular-weight heparins (LMWHs)?

    <p>LMWHs do not affect APTT, unfractionated heparin does</p> Signup and view all the answers

    What is the management of prolonged APTT without bleeding?

    <p>No further acute treatment is required</p> Signup and view all the answers

    What happens to intravenous heparins?

    <p>They are rapidly broken down</p> Signup and view all the answers

    Study Notes

    Theophylline Toxicity

    • Acute theophylline toxicity can cause dilated pupils, hallucinations, and convulsions.
    • Factors that inhibit CYP activity can alter theophylline clearance, leading to prolonged elimination after overdose.
    • Complications of theophylline toxicity include rhabdomyolysis, cardiac arrhythmias, and ventricular tachycardia or fibrillation.

    Therapeutic Range and Toxicity Assessment

    • Therapeutic range of theophylline concentrations: 10-20 mg/L (55-110 micromol/L).
    • Acute toxic effects correlate well with serum theophylline concentrations.
    • Plasma theophylline concentrations should be measured urgently in patients with clinical features of toxicity.
    • Repeat measurements every 2-4 hours in severe poisoning (>60 mg/L).

    Management of Theophylline Toxicity

    • Ensure a clear airway and adequate ventilation and oxygenation.
    • Monitor oxygen saturation, especially in patients with underlying respiratory disease.
    • Vitamin K can be used as a reversal agent in warfarin overdose.

    Warfarin Toxicity

    • Warfarin toxicity can cause bleeding, which is the most important clinical effect of anticoagulant excess.
    • Risk factors for warfarin toxicity include elderly individuals, patients with underlying clotting abnormalities, and patients with liver disease.
    • Genetic variability can affect warfarin dosing, and genetic factors may assist in preventing therapeutic over-anticoagulation.
    • Warfarin consists of R- and S-warfarin isomers, with S-warfarin being up to five times more potent than R-warfarin.

    Reversal Agent and Management of Warfarin Excess

    • Vitamin K can competitively reactivate vitamin K epoxide-reductase to overcome warfarin's action.
    • Speed of recovery depends on vitamin K dose and clotting factor re-synthesis rates.
    • Phenindione is an alternative vitamin K antagonist to warfarin, but it is more likely to cause adverse reactions.

    Long-Acting Anticoagulants

    • Difenacoum and brodifacoum are long-acting anticoagulants that are more potent than warfarin.
    • They have a very long duration of action, requiring prolonged therapy and monitoring over several months.

    Beta-Blocker Toxicity

    • Beta-blockers can cause competitive antagonism at the beta-adrenergic receptor.
    • Clinical effects may vary due to functional crossover between receptor subtypes.
    • Highly beta1 selective agents (e.g., bisoprolol, atenolol) have less affinity to beta2 receptor in respiratory tissue.
    • Non-selective agents (e.g., propranolol) have Na+ channel blocking effects sometimes termed 'quinidine-like effects' or 'membrane stabilizing activity'.
    • Partial agonist activity at adrenoceptors can lead to 'intrinsic sympathomimetic activity' (ISA).

    Management of Beta-Blocker Toxicity

    • Cardiovascular features of toxicity include bradycardia, hypotension, and heart block.
    • Treatment involves supportive care, including management of bradycardia and hypotension according to standard ALS algorithms.
    • Consider charcoal haemoperfusion or haemodialysis for severe toxicity.

    Heparin and Low-Molecular-Weight Heparins

    • Unfractionated heparin is a complex mixture of different molecular weights, not a single molecule.
    • Heparin breakdown products are smaller heparin-like molecules and are also active anticoagulants.
    • Low-molecular-weight heparins (LMWHs) avoid the problem of variable activity and have more activity against factor X and less against activated factor II.
    • LMWHs are normally prescribed as a weight-related dose, adjusted for renal function.
    • Monitoring of heparin effect is done using the activated partial thromboplastin time (APTT).

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