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Pharm1Test3LA
Pharm1 Test3 Local Anesthetics
| Question | Answer |
|---|---|
| Local anesthetics reversibly block the <blank> and <blank> of nerve impulses. | Generation and propagation. |
| What is bi-directional blockade? | Can block function in all excitable cells; thus can alter both sensory and motor function. |
| LA's level of effect depends on what four factors? | Agent used, route of administration, drug concentration at site, and lipophilicity. |
| What are the routes of LA administration? | Used topically on skin or mucous membranes, or peripheral, central and spinal via parenteral route. Also occasional use rectally or ophthalmically. |
| LA are some of the world's most widely used drugs. Some are also used as... | Antiarrhythmics. |
| The lipophilicity of the aromatic group controls the LA's ability to... | Penetrate the nerve sheath and enter the nerve membrane. |
| Most LA are weak bases that can exist in what two forms(will alter function at site)? | Freebase and positively charged form. |
| Most solutions are weakly acidic and alkalinization prior to use increases free base form which... | Increases lipid solubility and shortens onset time. |
| LA have lipophilic and hydrophilic regions. What is the lipophilic group? | Aromatic ring. |
| What is the LA's hydrophilic region? | Usually an amine (ionizable). |
| The LA's lipophilic and hydrophilic regions are joined by an amide or an ester, which is important for... | Metabolism and allergies. |
| Increasing lipid solubility <blank> onset time and <blank> duration. | Decreases, increases. |
| All usable LA have pKa's between... | 7.5-9.0 |
| LA act to decrease the permeability of the membrane to sodium ions. How? | These agents bind to sites in the Na+ channel of the voltage gated Na+ channels, thus inhibiting Na+ inflow during depolarization. |
| Low conc. of LA's decreases both the rate of rise and the height of the action potential. Higher concentrations can... | Abolish it totally. |
| What do LA do to the firing threshold and propagation time? | Increase them. |
| In myelinated fibers, where do LA's attack? | At the Nodes of Ranvier. |
| True or false. Sodium channel made up of an alpha subunit comprised of 16 additional subunits, and additional beta subunits. | False. Sodium channel made up of an alpha subunit comprised of 4 additional subunits, and additional beta subunits. |
| Where in the Sodium channel is the Sodium pore? | The alpha subunit. |
| LA bind to what kind of Sodium channel? | The closed, inactivated channel, freezing it in that form. |
| How is K ion flow affected by LA? | K+ outflow may also be inhibited somewhat, but not nearly to the extent of Na+. |
| How do LA's act? | Most act by binding to inner portion of Na+ channel. |
| In LA, small diameter nerves are affected first, then larger diameter nerves due to... | The number of channels to be blocked (greater in large fibers). |
| In LA, more rapidly stimulated fibers are also blocked first due to more frequent opening of Na+ channels, and the ability of the LA's to get into channel to bind. True or false? | True. |
| Sensory fibers tend to be triggered more frequently than motor fibers, and so tend to be... | Blocked first by LA. |
| What is the order of fibers affected by LA? | Autonomic, then sensory, then motor. |
| What are some natural toxins that kill by blocking Na channels? | Tetrodotoxin - from pufferfish and saxitoxin – from red tide microorganisms (paralytic shellfish poisoning), work by similar mechanism, blocking outer mouth of Na+ channel. |
| What is the order of recovery from fibers affected by LA? | Motor, sensory, autonomic. |
| How do LA work as antiarhythmics? | Due to the blockade of Na+ channels in myocardial tissues, with an effective decrease in firing rate, and passage of signals through conductive fibers. |
| How are LA used topically? | Decrease pain of wounds, burns, mucous membrane. |
| How are LA used via infiltration? | Injected around area - i.e. - for surgery. |
| How are LA used for regional nerve block? | Injected close to nerve that innervates the area to be anesthetized. |
| How are LA used for spinals? | Injected into lumbar subarachnoid space to get to nerves in that area going to various body sites. |
| How are LA used for epidurals? | Given inside spine above the dura mater. |
| How are LA used IV? | Usually for surgery on a specific limb. |
| Onset of anesthesia with LA is usually fastest with what two agents? | Lidocaine and Prilocaine. Procaine and tetracaine are slower. |
| Why is epi given with LA? | To attempt to increase duration. This is not always effective. |
| What locals have the shortest duration? | Procaine and Chloroprocaine (15-30 mins). |
| What locals have intermediate duration? | Lidocaine and Prilocaine (30-90 mins). |
| What local has the longest duration? | Tetracaine (2-3 hours). |
| Benzocaine shows the fastest onset when applied to mucous membranes, then... | Lidocaine and cocaine. |
| Duration for topical LA? | 30-60 mins. |
| Sensitivity reactions are more common with what kind of LA? | Esters. |
| Some LA preps include what additives that increase sensitivity risk? | Tartrazine and sulfites. |
| Systemic absorption of LA can lead to cardiotoxicity and what CNS symptoms? | Sedation, dizziness, disorientation, tremors, seizures, respiratory arrest. |
| Neurotoxicity is more common in what kinds of LA? | Epidural and subarachnoid. |
| Cauda equina syndrome can occur from epidurals and spinals. What is this? | Severe compression of the cauda equina resulting in loss of bowel or bladder function, loss of sensation in the buttocks and groin, and weakness in the legs. |
| What topical LA can cause methhemoglobinemia? | Prilocaine, Benzocaine, Lidocaine, Cetacaine. |
| What happens in methhemoglobinemia? | Oxidization of hemoglobin. |
| Except for allergic or hypersensitivity reactions, actual risk for most patients is fairly low. Why? | Due to their use in small amounts in a localized area for most procedures. |
| What is the metabolism of LA amides? | Primarily via hepatic microsomal enzymes. Metabolism via multiple steps |
| What is the metabolism of LA esters? | Metabolized by plasma and other esterases. |
| How are the LA classified? | By their structure, depending on whether the compound has an ester or amide linkage (or neither). |
| What are the LA esters? | Benzocaine (Oragel), Procaine (Novocain), Chloroprocaine (Nesacaine), Tetracaine (Pontocaine), Cocaine, and Cetacaine (Cetylite). |
| Why is Benzocaine(Oragel) only used topically? | It's poorly water soluble. |
| Excessive absorption of Benzocaine(Oragel) can lead to what? | Methemoglobinemia. |
| What is the pKa of Benzocaine(Oragel)? | 3.5. |
| What was the first synthetic LA? | Procaine(Novocaine). |
| Procaine(Novocaine) has a slower onset with <blank> duration and <blank> potency | Short, weak. |
| True or false: Procaine(Novocaine) is highly systemically toxic. | False. Fairly low systemic toxicity. |
| Procaine(Novocaine) is best used for... | Infiltration and nerve blocks. |
| Procaine(Novocaine)'s use has been superseded by what better agents? | Amides. |
| Chloroprocaine (Nesacaine) has a low systemic toxicity, a <blank> onset and <blank> duration. | rapid, short. |
| Since toxicity is low, Chloroprocaine(Nesacaine) is used in what concentrations? | High concentrations. |
| How is Chloroprocaine(Nesacaine) used? | Infiltration, nerve block, IV and epidurals. |
| Tetracaine(Ponticaine) is ten times more potent than Procaine, but also... | Ten times more toxic. |
| Tetracaine(Ponticaine) has a <blank> duration with <blank> onset. | Long, slow. |
| Why is Tetracaine(Ponticaine) mainly used in spinal anesthesia? | Barriers decrease diffusion and decrease toxicity risk. |
| Tetracaine(Ponticaine) is active topically, but what limits its use? | Absorption across mucous membranes. |
| Cocaine is derived from what part of the coca plant? | The leaves. |
| What level controlled substance is Cocaine? | C-II. |
| Cocaine is too toxic for use other than... | Topically. |
| In addition to its LA effect, Cocaine has potent... | Vasoconstrictive and addictive effects. |
| When do we usually use Cocaine in anesthesia? | Topically on mucous membranes, such as nasal cavities or oropharyngeal cavities prior to surgery, and packed post-op to decrease bleeding and pain. |
| Cetacaine (Cetylite) is a topical agent for local skin disorders and is used on various mucous membranes, except... | The eye. |
| Cetacaine(Cetylite) is a mixture of what three drugs? | Benzocaine, Tetracaine, and Butyl Aminobenzoate. |
| When do we use Cetacaine(Cetylite)? | Topically, rectally or as a spray to inhibit the gag reflex (during bronchoscope exam, etc). |
| What are the LA amides? | Lidocaine (Xylocaine), Prilocaine (Citanest), Mepivacaine (Carbocaine), Bupivacaine (Marcaine), Articaine (Septocaine), and Ropivacaine (Naropin). |
| What is the most commonly used LA? | Lidocaine(Xylocaine). |
| Lidocaine(Xylocaine) has <blank> onset with <blank> duration | Rapid, intermediate. |
| Lidocaine(Xylocaine) causes vasodilation, so many formulations contain... | Epinephrine. |
| Prilocaine (Citanest) is similar to Lidocaine in properties, but less... | Vasodilation. |
| Prilocaine(Citanest) has <blank> onset with <blank> duration. | Rapid, intermediate. |
| True or false: Prilocaine(Citanest) causes methemoglobinemia most often of the amides. | False. It is the least toxic of the amides, but can still cause methemoglobinemia. |
| Mepivacaine(Carbocaine) is used similarly to Lidocaine. How is it used? | Infiltration, nerve block, epidural. |
| True or false. Mepivacaine(Carbocaine) is a topical anesthetic. | False. Has no topical effect. |
| Why don't we use Mepivacaine(Carbocaine) in OB? | Biotransformation in fetus is prolonged. |
| Mepivacaine(Carbocaine) is a racemic mixture. It is similar to what other two anesthetics? | Bupivacaine and Ropivacaine. |
| True or false: Bupivacaine(Marcaine) is a highly potent drug with a long duration and slower onset. | True. |
| How does the toxicity of Bupivacaine(Marcaine) compare to Lidocaine(Xylocaine)? | It is much more toxic(cardiotoxic). |
| How is Bupivacaine(Marcaine) used? | Infiltration nerve block, epidural and spinal anesthesia. |
| Bupivacaine(Marcaine) is more likely to cause... | Adverse effects. |
| Articaine (Septocaine) is only available in U.S. in combination with... | Epinephrine. |
| Articaine(Septocaine) has a rapid onset and short duration. When is it used? | Dental and periodontal procedures. |
| Why does Articaine(Septocaine) have such rapid metabolism? | It has both an ester and an amide group. |
| Articaine(Septocaine) has a low toxicity due to its... | Rapid metabolism. |
| Ropivacaine (Naropin) has a long duration, similar to Bupivacaine, but less... | Cardiotoxic. |
| Bupivacaine's cardiotoxicity is due to what isomer? | R-isomer. |
| Ropivicaine(Naropin) is purified and contains only what isomer? | S-isomer. |
| Less lipid soluble, and more rapidly <blank> than Bupivacaine. | Metabolized. |
| How do we use Ropivicaine(Naropin)? | Infiltration, nerve block, epidural, spinal. |
| What LA is neither an amide nor an ester? | Pramoxine (Proctofoam). |
| How is Pramoxine(Proctofoam) used? | Topical agent for relief of hemorrhoids, rectal pain and itching of skin disorders (pruritus). |
| What is Pramoxine(Proctofoam) commonly mixed with? | Many products (ex. Hydrocortisone, calamine). |
| True or false: Pramoxine(Proctofoam) is used to abolish the gag reflex. | False. It has a weak potency and will not completely obliterate the gag reflex. |
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