Local Anaesthetics Properties
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Questions and Answers

What is the mechanism of action of local anesthetics on nociceptors?

  • Increasing the release of neurotransmitters from nociceptors
  • Blocking the action potential by blocking voltage-gated K+ channels
  • Decreasing the sensitivity of nociceptors to noxious stimuli
  • Blocking the action potential by blocking voltage-gated Na+ channels (correct)

    • Which of the following local anesthetics is metabolized in the liver by dealkalisation?

  • Articaine
  • Bupivacaine (correct)
  • Lidocaine
  • Prilocaine

    • Which of the following factors affects the tissue absorption of local anesthetics?

  • pH and ionization
  • Lipid solubility
  • Potency and pKa
  • All of the above (correct)

    • Which of the following local anesthetics is known to cause methaemoglobinemia?

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

    Which of the following local anesthetics has the highest lipid solubility?

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

    What is the primary mechanism of action of local anaesthetics?

    <p>By inhibiting the influx of sodium ions through voltage-gated channels</p> Signup and view all the answers

    What factor affects the tissue absorption of local anaesthetics?

    <p>Lipid solubility</p> Signup and view all the answers

    How does local pH affect the action of local anaesthetics?

    <p>Increased pH decreases the action of local anaesthetics</p> Signup and view all the answers

    What is the relationship between pKa and potency of local anaesthetics?

    <p>Lower pKa values result in higher potency</p> Signup and view all the answers

    Why is lipid solubility important for local anaesthetics?

    <p>It affects the tissue absorption</p> Signup and view all the answers

    What is the form of local anaesthetics that penetrates both the tissue and nerve membrane?

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

    What is the effect of an acidic pH on the absorption of local anaesthetics?

    <p>Decrease in absorption</p> Signup and view all the answers

    What is the significance of pKa value in local anaesthetics?

    <p>It is the pH at which 50% of the drug is ionised and 50% is present as a base</p> Signup and view all the answers

    What is the effect of higher pKa values on the potency of local anaesthetics?

    <p>Decrease in potency</p> Signup and view all the answers

    What is the effect of greater lipid solubility on the potency of local anaesthetics?

    <p>Increases potency</p> Signup and view all the answers

    What is the maximum safe dose of lidocaine/lignocaine for a patient?

    <p>500mg</p> Signup and view all the answers

    Which of the following local anesthetics has a short duration of action and is used for infiltration and nerve block?

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

    What is the pKa of articaine, which affects its ionization and potency?

    <p>7.8</p> Signup and view all the answers

    Which of the following local anesthetics has a high lipid solubility and is used for epidurals?

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

    What is the duration of action of lidocaine/lignocaine without adrenaline?

    <p>1.5 hours</p> Signup and view all the answers

    What type of nerve fibres are most affected by local anaesthetics?

    <p>Smaller neuronal alpha-delta (A-δ) fibres</p> Signup and view all the answers

    What determines the plasma concentration of local anaesthetics?

    <p>The dose of the drug administered</p> Signup and view all the answers

    What is a common symptom of central nervous system toxicity of local anaesthetics?

    <p>Light-headedness</p> Signup and view all the answers

    What is a common allergenic compound produced during the metabolism of ester-type local anaesthetics?

    <p>Para-aminobenzoic acid (PABA)</p> Signup and view all the answers

    What is an important consideration when choosing a local anaesthetic for dentistry in pregnant women?

    <p>Avoiding octapressin</p> Signup and view all the answers

    What is the primary method of administration for local anaesthetics?

    <p>Topical application or local injection</p> Signup and view all the answers

    Why do amino ester local anaesthetics have a shorter half-life?

    <p>Because they are metabolized by cholinesterase enzymes</p> Signup and view all the answers

    What is unique about cocaine as a local anaesthetic?

    <p>It causes vasoconstriction by inhibiting noradrenaline re-uptake</p> Signup and view all the answers

    What determines the potency of a local anaesthetic?

    <p>The lipid solubility of the local anaesthetic</p> Signup and view all the answers

    What is the significance of the pKa of a local anaesthetic?

    <p>It determines the degree of ionization of the local anaesthetic</p> Signup and view all the answers

    What is the primary factor that determines the duration of action of local anesthetics?

    <p>Lipid solubility</p> Signup and view all the answers

    What is the effect of vasoconstrictors on the local anaesthetic action?

    <p>Faster onset of anaesthesia</p> Signup and view all the answers

    What is the order of blockade of nerve fibres when a local anesthetic is deposited in proximity to a peripheral nerve?

    <p>Outer mantle to core</p> Signup and view all the answers

    What is the function of adrenaline (epinephrine) in local anaesthetics?

    <p>Acts as a vasoconstrictor</p> Signup and view all the answers

    What is the consequence of vasoconstriction on the local anaesthetic half-life?

    <p>Longer half-life</p> Signup and view all the answers

    What is the advantage of using felypressin (octapressin) as a vasoconstrictor?

    <p>It has a weaker effect on cardiac response</p> Signup and view all the answers

    What is the effect of vasoconstrictors on operative and post-operative haemorrhage?

    <p>Reduction in haemorrhage</p> Signup and view all the answers

    What is the classification of local anaesthetics based on their duration of action?

    <p>Short, intermediate, and long acting</p> Signup and view all the answers

    What is the consequence of using a local anaesthetic with a higher lipid solubility?

    <p>Faster onset of anaesthesia</p> Signup and view all the answers

    What is the disadvantage of using vasoconstrictors in local anaesthetics?

    <p>Alterations in cardiovascular response</p> Signup and view all the answers

    What is the primary mechanism by which pseudocholinesterase enzyme metabolizes ester-type local anesthetics in plasma?

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

    Which of the following factors affects the tissue absorption of local anesthetics?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of a lower pKa value on the potency of local anesthetics?

    <p>Increased potency</p> Signup and view all the answers

    What is the significance of lipid solubility in local anesthetics?

    <p>It affects the tissue absorption of local anesthetics</p> Signup and view all the answers

    What is the effect of acidic pH on the ionization of local anesthetics?

    <p>Increased ionization</p> Signup and view all the answers

    What is the primary site of action of local anaesthetics?

    <p>Voltage-gated Na+ channels</p> Signup and view all the answers

    What is the effect of acidic pH on the absorption of local anaesthetics?

    <p>Decreased absorption</p> Signup and view all the answers

    What is the relationship between pKa and potency of local anaesthetics?

    <p>Lower pKa values result in higher potency</p> Signup and view all the answers

    Why is lipid solubility important for local anaesthetics?

    <p>It affects the tissue absorption of the anaesthetic</p> Signup and view all the answers

    What determines the potency of a local anaesthetic?

    <p>All of the above</p> Signup and view all the answers

    What is the form of local anaesthetics that binds to the inactivation site of the Na+ channel, keeping the channel closed?

    <p>Ionic form (BH+)</p> Signup and view all the answers

    What is the effect of an acidic pH on the absorption of local anaesthetics?

    <p>Decreases absorption</p> Signup and view all the answers

    What determines the equilibrium between the lipid-soluble base (B) and the ionic form (BH+)?

    <p>Both A and B</p> Signup and view all the answers

    What is the effect of a lower pKa value on the onset of action of local anaesthetics?

    <p>Speeds up the onset of action</p> Signup and view all the answers

    What is the consequence of greater lipid solubility on the potency and duration of local anaesthetics?

    <p>Increases potency and duration</p> Signup and view all the answers

    What is the primary mechanism of action of local anaesthetics on nerve fibres?

    <p>They block the sodium channels</p> Signup and view all the answers

    What is the main factor that affects the tissue absorption of local anaesthetics?

    <p>The lipid solubility of the drug</p> Signup and view all the answers

    What is the effect of acidic pH on the ionization of local anaesthetics?

    <p>It increases the ionization of the local anaesthetic</p> Signup and view all the answers

    What is the relationship between pKa and potency of local anaesthetics?

    <p>Lower pKa values result in higher potency</p> Signup and view all the answers

    What is the significance of lipid solubility in local anaesthetics?

    <p>It affects the potency of the local anaesthetic</p> Signup and view all the answers

    What is the primary factor that determines the potency of local anesthetics?

    <p>Lipid solubility</p> Signup and view all the answers

    What happens to the ionization of local anesthetics in an acidic pH?

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

    What is the significance of pKa in local anesthetics?

    <p>Determines the potency of the anesthetic</p> Signup and view all the answers

    What determines the tissue absorption of local anesthetics?

    <p>All of the above</p> Signup and view all the answers

    What is the advantage of using a local anesthetic with higher lipid solubility?

    <p>Greater potency</p> Signup and view all the answers

    What is the primary mechanism by which local anaesthetics act on nerve endings?

    <p>Blocking the action potential in nerve fibres</p> Signup and view all the answers

    What is the primary factor that affects the tissue absorption of local anaesthetics?

    <p>Lipid solubility of the anaesthetic</p> Signup and view all the answers

    What happens to the ionization of local anaesthetics in an acidic pH environment?

    <p>It increases the ionization of the anaesthetic</p> Signup and view all the answers

    What is the relationship between pKa and potency of local anaesthetics?

    <p>Lower pKa values result in higher potency</p> Signup and view all the answers

    Why is lipid solubility important for local anaesthetics?

    <p>It affects the tissue absorption of the anaesthetic</p> Signup and view all the answers

    What happens to the nerve fibers located in the outer mantle of the nerve when a local anesthetic is deposited in proximity to a peripheral nerve?

    <p>They are blocked first</p> Signup and view all the answers

    How does the presence of vasoconstrictors affect the duration of action of local anesthetics?

    <p>It increases the duration of action</p> Signup and view all the answers

    What is the result of adding vasoconstrictors to local anesthetics on operative and post-operative haemorrhage?

    <p>It decreases haemorrhage</p> Signup and view all the answers

    What is the classification of local anesthetics based on their duration of action?

    <p>Short, intermediate, and long acting</p> Signup and view all the answers

    What is the effect of lipid solubility on the potency of local anesthetics?

    <p>Higher lipid solubility increases potency</p> Signup and view all the answers

    What is the primary mechanism of action of vasoconstrictors in local anesthetics?

    <p>They decrease blood flow</p> Signup and view all the answers

    How does the concentration of vasoconstrictors affect their action?

    <p>Higher concentrations increase their action</p> Signup and view all the answers

    What is the disadvantage of using vasoconstrictors in local anesthetics?

    <p>They alter cardiovascular response</p> Signup and view all the answers

    How does the presence of vasoconstrictors affect the local anaesthetic half-life?

    <p>It increases the half-life</p> Signup and view all the answers

    What is the effect of vasoconstrictors on the onset of anaesthesia?

    <p>It hastens the onset of anaesthesia</p> Signup and view all the answers

    What is the effect of a lower pKa value on the potency of local anaesthetics?

    <p>It increases the potency</p> Signup and view all the answers

    What determines the tissue absorption of local anaesthetics?

    <p>Lipid solubility of the anaesthetic</p> Signup and view all the answers

    What is the primary mechanism of action of local anaesthetics on nociceptors?

    <p>Blocking voltage-gated sodium channels</p> Signup and view all the answers

    What determines the potency of a local anaesthetic?

    <p>Lipid solubility</p> Signup and view all the answers

    What is the effect of acidic pH on the ionization of local anaesthetics?

    <p>It increases the ionization</p> Signup and view all the answers

    What is the effect of increasing pH on the ionization of local anaesthetics?

    <p>Reduced ionization and increased potency</p> Signup and view all the answers

    What is the primary determinant of the equilibrium between the ionized and nonionized forms of local anesthetics?

    <p>pH of the tissues</p> Signup and view all the answers

    What determines the rate of tissue absorption of local anaesthetics?

    <p>pKa value and pH of the tissue</p> Signup and view all the answers

    In which form do local anesthetics bind to the inactivation site of the Na+ channel?

    <p>Ionized (BH+) form</p> Signup and view all the answers

    What is the primary mechanism of action of local anaesthetics on nerve conduction?

    <p>Inhibition of sodium ion influx</p> Signup and view all the answers

    What is the relationship between pKa and potency of local anaesthetics?

    <p>Lower pKa values result in higher potency</p> Signup and view all the answers

    What is the consequence of a higher pKa value for local anesthetics?

    <p>Slower onset of action</p> Signup and view all the answers

    What is the primary reason why local anesthetics are less effective in inflamed tissue?

    <p>Decreased pH</p> Signup and view all the answers

    What is the significance of lipid solubility in local anaesthetics?

    <p>It affects the potency and tissue absorption</p> Signup and view all the answers

    What is the effect of greater lipid solubility on the duration of action of local anesthetics?

    <p>Increased duration</p> Signup and view all the answers

    What is the primary factor that affects the absorption of local anaesthetics into the nerve tissue?

    <p>Lipid solubility of the anaesthetic</p> Signup and view all the answers

    What is the significance of the pKa of a local anaesthetic?

    <p>It affects the potency of the anaesthetic</p> Signup and view all the answers

    What is the main mechanism of action of local anaesthetics on nerve fibres?

    <p>They block the conduction of impulses along the nerve fibre</p> Signup and view all the answers

    What is the effect of acidic pH on the ionization of local anaesthetics?

    <p>It increases the ionization of the anaesthetic</p> Signup and view all the answers

    What determines the lipid solubility of a local anaesthetic?

    <p>The structure of the anaesthetic molecule</p> Signup and view all the answers

    What is the effect of a higher pKa value on the potency of local anaesthetics?

    <p>It decreases the potency</p> Signup and view all the answers

    What is the primary mechanism by which local anaesthetics block nerve conduction?

    <p>By inhibiting sodium channels</p> Signup and view all the answers

    What is the effect of lipid solubility on the potency of local anaesthetics?

    <p>It increases the potency</p> Signup and view all the answers

    What is the effect of acidic pH on the ionization of local anaesthetics?

    <p>It increases ionization</p> Signup and view all the answers

    What is the significance of pKa in local anaesthetics?

    <p>It determines the ionization</p> Signup and view all the answers

    What is the effect of an acidic pH on the ionization of local anesthetics?

    <p>Increases the ionization of local anesthetics</p> Signup and view all the answers

    What is the primary mechanism by which lipid solubility affects the potency of local anesthetics?

    <p>Increased lipid solubility allows for faster diffusion across the nerve membrane</p> Signup and view all the answers

    What is the primary mechanism of action of local anesthetics on nociceptors?

    <p>Blocking the sodium channels on the nerve membrane</p> Signup and view all the answers

    What is the significance of pKa in local anesthetics?

    <p>pKa determines the ionization of local anesthetics at physiological pH</p> Signup and view all the answers

    What is the effect of higher lipid solubility on the tissue absorption of local anesthetics?

    <p>Higher lipid solubility increases the tissue absorption of local anesthetics</p> Signup and view all the answers

    What is the effect on the potency of a local anaesthetic if its pKa value is decreased?

    <p>It increases</p> Signup and view all the answers

    Why do local anaesthetics with higher lipid solubility have a longer duration of action?

    <p>They are more tightly bound to nerve membranes</p> Signup and view all the answers

    What is the mechanism by which local anaesthetics block nerve conduction?

    <p>They block sodium channels</p> Signup and view all the answers

    What is the effect of acidic pH on the ionization of local anaesthetics?

    <p>It increases the unionized form</p> Signup and view all the answers

    What is the primary factor that determines the tissue absorption of local anaesthetics?

    <p>Lipid solubility</p> Signup and view all the answers

    What is the effect of vasoconstrictors on the duration of action of local anaesthetics?

    <p>It increases the duration of action</p> Signup and view all the answers

    What is the effect of higher lipid solubility on the potency of local anaesthetics?

    <p>It increases the potency</p> Signup and view all the answers

    What is the relationship between pKa and potency of local anaesthetics?

    <p>A lower pKa value increases potency</p> Signup and view all the answers

    What is the mechanism by which vasoconstrictors, such as adrenaline, increase the duration of action of local anaesthetics?

    <p>They decrease the blood flow to the injection site</p> Signup and view all the answers

    What is the effect of a higher pKa value on the potency of local anaesthetics?

    <p>It decreases the potency</p> Signup and view all the answers

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