2 - Local Anaesthetics Flashcards
Local anaesthetics are either:
(1) Injectable
(2) Topical
True
Injectable anaesthetics are:
(1) Amide - Bupivacaine, Lignocaine, Mepivacaine
(2) Ester - Procaine, Cocaine, Tetracaine
(3) Antihistamines - Diphenhydramine
True
Topical anaesthetics are:
(1) Amide - Dibucaine, Lignocaine, Mixture of Lignocaine + Prilocaine (EMLA)
(2) Ester - Benzocaine
(3) Ether - Pramoxine
(4) Ketone - Diclonine
(5) Antihistamines - Diphenhydramine, Doxepine
(6) Substance P depletors - Capsaicin
True
EMLA = eutectic mixture of local anaesthetics
Both amide (lignocaine, Mepivacaine, Bupivacaine) and ester (procaine, benzocaine) local anaesthetic compounds have an aromatic (lipophilic) portion, an amine (hydrophilic) portion, and an intermediate chain (ester or amide)
True
Lipophilicity (from protein binding) appears to correlate with the intrinsic potency of the anaesthetic
True (Bupivacaine is highly lipophilic compared to lignocaine and therefore much more potent, with a longer duration of action)
Absorption of lignocaine (amide) and other injectable local anaesthetics into the systemic circulation in influenced by properties of the agent itself
True
Absorption of lignocaine (amide) and other injectable local anaesthetics into the systemic circulation in influenced by presence of a vasoconstrictor in the injected solution
True (adrenaline reduces absorption)
Absorption of lignocaine (amide) and other injectable local anaesthetics into the systemic circulation in influenced by quantity of the drug injected
True
Absorption of lignocaine (amide) and other injectable local anaesthetics into the systemic circulation in influenced by technique of the injection
True
With the exception of cocaine (has potent vasoconstrictive effects), all other local anaesthetics have varying degrees of vasodilator effects and adrenaline is often added for its haemostatic effect
True
The vasoconstriction caused by adrenaline delays the absorption of the anaesthetic agent, thereby prolonging the anaesthetic effect
True
Without adrenaline, the approximate duration of action of lignocaine is 30-60 mins
True
With adrenaline, the duration of action of lignocaine is extended to 120-360 mins
True (Without adrenaline, the approximate duration of action of lignocaine is 30-60 mins)
Skin and subcutaneous tissues of the face and scalp exhibit higher significant absorption than the trunk or extremities owing to the increase relative density of blood vessels, therefore duration of anaesthesia may be briefer in these highly vascularised areas
True
Injection of the Anaesthetic agents too deeply into subcutaneous fat may give inadequate analgesia particularly on the scalp, resulting in the requiremeant for larger volumes of local anaesthetic injection and increased systemic drug absorption
True
Incorrect local anaesthetic infiltration technique may also lead to direct intravascular injection and risking systemic toxicity
True
Protein binding is the property of local anaesthetics that relates to the relative lipophilicity of the agent
True
Lignocaine = 60-80% protein bound with elimination half-life of 1.5-2 hours
Bupivacaine = 82-96% protein bound with elimination half-life of 5 hours
Amide local anaesthetics (lignocaine, Bupivacaine, Mepivacaine, prilocaine) is metabolised in the liver through hydrolysis by hepatic microsomal enzymes (Cytochrome P450) in the endoplasmic reticulum of hepatocytes
True (metabolism can be dramatically impaired in patients with significant liver dysfunction, therefore putting the patients at risk for systemic toxicity when relatively high volumes are used)
Metabolism of amide local anaesthetics (lignocaine, Bupivacaine, Mepivacaine, prilocaine) can be dramatically impaired in patients with significant liver dysfunction, therefore putting the patients at risk for systemic toxicity when relatively high volumes are used
True (metabolised in the liver by microsomal Cytochrome P450 enzymes)
Lignocaine is specifically metabolised by CYP3A4
True (substrate of CYP3A4)
Ester local anaesthetics (procaine, benzocaine) are metabolised very rapidly in the blood by pseudocholinesterase through hydrolysis to form aromatic acids and amino alcohols
True (in contrast, amides are metabolised in the liver) - approx 4% of the population is deficient in pseudocholinesterase, potentially resulting in slow metabolism
Both amides (lignocaine, Bupivacaine, Mepivacaine, prilocaine) and esters (procaine, benzocaine) are eliminated through renal excretion
True
Lignocaine has a complex excretion process as it is metabolised by CYP3A4 in the liver and then excreted into the bile , but is then reabsorbed from the GI tract and excreted in the urine
True (simplified version = metabolised in the liver, excreted in the kidneys)
Amide and Ester Local anaesthetics prevent nerve depolarisation/block conduction in nerves by minimising or preventing the influx of sodium ions into the nerve axon cell membrane
True (lipophilic portion of the drug allows penetration of the cell membrane, hydrophilic portion of the drug interact with the sodium channels on the inner surface of the cell membrane)
Through prevention of nerve depolarisation, amide and ester local anaesthetics block type C pain and itch nerve fibres
True
Local anaesthetics work on all nerves although have different propensities to block conduction depending on the nerve characteristics
True (Small diameter myelinated nerves such as pain and temperature fibres I.e. Type A delta fibres are more sensitive to blockade by local anaesthetics)
Small diameter myelinated nerves are more sensitive to blockade by local anaesthetics
True (relevant small myelinated nerve fibres are the type A delta fibres that carry pain and temperature sensations)
The larger myelinated nerve fibres are more resistant to blockade by local anaesthetics
True (larger myelinated nerve fibres are the type A alpha fibres that carry touch and pressure sensations)
The largest myelinated nerve fibres are most resistant to local anaesthetic blockade
True (the largest and most resistant myelinated nerve fibres are the type A alpha fibres that control propioception and motor function)
Myelinated nerve fibres are more resistant to local anaesthetics that unmyelinated nerve fibres
True
Temporary motor paresis may occur if high volumes of local anaesthetic are used
True
Temporary motor paresis may occur if dep placement of the local anaesthetic occurs in an area where deeper motor fibres are present under the more superficial sensory cutaneous nerves
True (can be seen commonly when anaesthetising skin on the temple overlying the temporal branch of the facial nerve)
The maximum dose of lignocaine without adrenaline is 4.5mg/kg (up to 300mg)
True (lignocaine concentration is 1mg/ml)
The maximum dose of lignocaine with adrenaline is 7mg/kg (up to 500mg)
True (lignocaine concentration is 1mg/ml)
The duration of action of Bupivacaine is 120-240 mins when used without adrenaline
True
The duration of action of Bupivacaine is 180-420 mins when used with adrenaline
True
The maximum dose of Bupivacaine without adrenaline is 175mg
True
The maximum dose of Bupivacaine with adrenaline is 225mg
True
The onset of action of lignocaine is <2 mins
True
The onset of action of Bupivacaine is 5 mins
True
Lignocaine is FDA approved for:
(1) infiltrative anaesthesia
(2) regional nerve block
(3) topical anaesthesia
True
Lignocaine is used off-label for:
(1) tumescent anaesthesia
(2) postherpetic neuralgia
(3) pruritus
True
Papillary dermal injection is most painful and creates more tissue distortion but gives instantaneous anaesthesia and such a depth of injection may be indicated in situations that require very rapid onset of anaesthesia
True
Subcutaneous is the least painful plane of injection, however this depth of injection provides less effective anaesthesia for epidermal and dermal procedures unless the anaesthetic is allowed to diffuse into adjacent tissue planes over several minutes
True
A favoured method of infiltration involves injection anaesthetic slowly as the needle is advanced into the deep dermis at the junction of the subcutaneous tissue as this method strikes a balance allowing relatively rapid onset of anaesthesia with less injection pain
True
Use of pH-buffered lignocaine (achieved using 1 part sodium bicarbonate with 9 parts lignocaine) reduces pain of injection
True
Warming the local anaesthetic to 40 degree Celsius can reduce injection pain
True
Adding hyaluronidase to lignocaine results in enhanced tissue dispersion of lignocaine and less tissue distortion, although it increases the pain of injection and reduces the duration of anaesthesia
True (also contains thimerosal, to which patents may be allergic)
Placing lignocaine-soaked gauze in an open wound for several minutes to allow topical absorption of the local anaesthetic prior to re-injection for lacerations and in MOHs surgery
True
Ring blocks may be useful in obtaining skin biopsies for microbiologic culture as direct infiltration of the anaesthetic with preservatives into the tissue to be smokes may lead to false negative bacterial cultures owing to the antibacterial effects of the preservatives
True
Regional nerve blocks are commonly used on the face, wrist, ankle, and digits and is useful to treat large areas such as for facial laser resurfacing
True (2% lignocaine commonly used -no need for adrenaline as no vasoconstriction needed)
The main risks with regional nerve block include laceration of nerve trunks
True
The main risks with regional nerve block include intravascular injection
True
The main risks with regional nerve block include temporary motor paralysis
True
The tumescent technique achieves longer lasting regional anaesthesia by direct infiltration of large volumes of dilute lignocaine with lower concentrations of adrenaline
True
Adverse effects of local anaesthetics are uncommon
True (adverse effects of the vasoconstrictive agent is more common than the actual anaesthetic agent itself)
Adverse reactions to local anaesthetics can be toxic or allergic in nature
True
Lignocaine toxicity primarily involves CNS toxicity and Cardiotoxicity
True
CNS toxicity = drowsiness, circumoral paraesthesia, lingual paraesthesia, tinnitus, nystagmus, ataxia, hallucinations, twitching, anxiety, restlessness, tremor, seizures, coma, apnoea
The is an overlap between the signs and symptoms of lignocaine toxicity and systemic effects of adrenaline such as anxiety, restlessness and tremor
True (given that the lignocaine dose limit is not exceeded, it can be assumed that these symptoms are from adrenaline + the absence of tinnitus and circumoral paraesthesia also supports the effects are due to adrenaline instead)
IV lipid emulsion (20%) infusion has been safely used and effectively improve survival and reverse the CNS and cardiovascular symptoms of lignocaine toxicity
True
The effects of lignocaine toxicity on the cardiovascular system are due to blocking of sodium channels which leads to decreased cardiac contractility, hypotension, bradycardia, and respiratory depression
True (Bupivacaine also exerts the sa,e effect, but 4 X more potency than lignocaine as a reflection of its potency compared to lignocaine)
Bupivacaine toxicity may also cause fatal dysrhythmias (ventricular fibrillation) as it dissociates more slowly/incompletely from the sodium channels
True
Allergic reaction make up <1% of all adverse reactions to local anaesthetics
True
Local anaesthetic allergic reaction may either be due to the:
(1) anaesthetic itself (true anaesthetic allergy)
(2) preservatives such as parabens and sulfites
True (esters are more commonly associated with allergic reactions)
Esters are more commonly associated with allergic reactions than amides
True (one of the primary factors leading to decline in usage of esters)
The 2 types of allergic reaction to local anaesthetics are:
1) anaphylactic reactions (type I IgE hypersensitivity
(2) delayed reactions (type IV hypersensitivity)
True
There is no cross-reaction between amides and esters
True (from patch testing results) - although if the patient has had an anaphylactic reaction then thorough evaluation by an allergist is recommended as class switching in anaphylaxis reactions has never been proven to be completely safe
If no safe local anaesthetic can be determined based on allergic reaction history, infiltration of diphenhydramine (antihistamine) or even saline can provide reasonable local anaesthesia in selected instances
True
Transient or minor reactions frequently caused by adrenaline include anxiety
True
Transient or minor reactions frequently caused by adrenaline include headache
True
Transient or minor reactions frequently caused by adrenaline include tremor
True
Transient or minor reactions frequently caused by adrenaline include restlessness
True
Transient or minor reactions frequently caused by adrenaline include palpitations
True
Vasovagal reactions may occur due to the injection procedure and are not an effect of the local anaesthetic agent
True
Drugs that induce CYP3A4 system may theoretically increase lignocaine clearance and reduce lignocaine blood levels
True (lignocaine is a substrate of CYP3A4 metabolism in the liver) - this has no clinical signifance in dermatologic use as rapid clearance would only enhance the safety profile of its use
Drugs that inhibit CYP3A4 system may theoretically reduce lignocaine clearance and increase lignocaine blood levels
True (consider reducing the doses lignocaine for tumescent anaesthesia and when administering large volumes of infiltrative anaesthesia)
Bupivacaine offers prolonged duration of anaesthesia as much as 4X the duration of plain lignocaine, although it’s onset of action may be slower
True (due to lipid solubility)
More lipid soluble anaesthetic agents (Bupivacaine) are more potent, and this increased potency correlates with increased potential for both CNS toxicity and cardiovascular toxicity
True
Lignocaine is classified as pregnancy category B and the use during pregnancy is generally acceptable, but should be considered cautiously
True (Bupivacaine and Mepivacaine are relatively contraindicated owing to the risk of Fetal bradycardia)
Adrenaline is classified as pregnancy category C, although it is believed that it is unlikely that doses used in dermatologic surgery would have significant effect
True (it is prudent to discuss the use of any medication in pregnancy with the patient’s obstetrician if any questions arise)
EMLA (eutectic mixture of local anaesthetics) is the prototype topical anaesthetic cream consisting of lignocaine and prilocaine (both amides)that can deliver adequate skin analgesia
True
Lignocaine 2.5%
Prilocaine 2.5%
Mixing the crystalline forms of lignocaine and prilocaine in a 1:1 ratio (EMLA) gives this combination a lower melting point than either agent alone
True (eutectic mixture which is a liquid at room temperature and subsequently able to be suspended in an oil in water emulsion)
Lignocaine 2.5%
Prilocaine 2.5%
EMLA is a highly concentrated Louis combination of lignocaine and prilocaine that promotes enhanced penetration over the crystalline form of either drug individually in a cream base
True (as the melting point is lower for the drugs combined than either agent alone)
The amount or a large systemically absorbed depends on the duration and surface area of application
True (skin blood flow, skin thickness and presence of skin pathology lead to altered absorption)
Skin blood flow, skin thickness (particularly of the stratum corneum) and presence of skin pathology lead to altered absorption of EMLA
True
Skin blood flow, skin thickness (particularly of the stratum corneum) and presence of skin pathology affects the onset of action of EMLA
True
Skin blood flow, skin thickness (particularly of the stratum corneum) and presence of skin pathology affects the efficacy of EMLA
True
Skin blood flow, skin thickness (particularly of the stratum corneum) and presence of skin pathology affects the duration of action of EMLA
True
EMLA is absorbed faster on the face
True
Prilocaine (amide) is metabolised in the liver by hepatic microsomal cytochrome P450 enzymes similar to lignocaine, but at a faster rate
True
Prilocaine (amide) is excreted in the kidney
True (similar to lignocaine)
EMLA is FDA approved of topical analgesia of normal intact skin
True
If EMLA is applied under an occlusive dressing such as Tegaderm in a quantity of 1-2g/10cm2, the onset of significant analgesia occurs by approximately 60 mins
True
There is onset of dermal analgesia if EMLA is continuously occluded for up to 3 hours, and this effect persists for up to 1-2 hours after removal of the cream
True
The depth of analgesia from EMLA up to a maximum of 5mm, increases with increasing duration of application
True
EMLA has been FDA approved as pre-operative analgesia before laser surgery
True (treating port wine stains, laser-assisted hair removal)
EMLA is FDA approved to achieve analgesia during ulcer debridement
True
EMLA has been used for postherpetic neuralgia
True (but the large area to be treated and the need for occlusion limits the routine use of EMLA in this situation)
EMLA cream may cause systemic effects and local effects
True
Methaemoglobinaemia is the most serious systemic effect of EMLA cream, and is a unique effect of Prilocaine
True (a metabolite of Prilocaine is thought to cause oxidation of haemoglobin to methaemoglobin, which has a reduced the oxygen carrying capacity than normal haemoglobin as the release of oxygen is less efficient) - patients at risk of methaemoglobinaemia should not use EMLA
Methaemoglobinaemia from Prilocaine (as a component of EMLA cream) results in tissue hypoxia
True
Patients at risk for methaemoglobinaemia should not use EMLA (includes patients with congenital or idiopathic methaemoglobinaemia and infants under 12 months taking any methaemoglobin-inducing agents)
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
Methaemoglobinaemia induced by Prilocaine (in EMLA cream) either resolves spontaneously or can be hastened by IV methylene blue in severe symptomatic cases
True
Sites treated with EMLA can experience stinging
True
Sites treated with EMLA can experience burning
True
Sites treated with EMLA can experience pruritus
True
Sites treated with EMLA can experience blanching
True
Sites treated with EMLA can experience erythema
True
Sites treated with EMLA can experience contact urticaria
True
Sites treated with EMLA can experience purpura
True
Sites treated with EMLA can experience petechia
True
Allergic contact dermatitis to the Prilocaine within EMLA cream can occur
True
Corneal abrasions may occur when EMLA is applied near the eyes for patient undergoing facial laser treatments
True (extreme caution should be exercised in this area because the alkalinity of the EMLA product can result in a chemical burn, the symptoms of which may be masked at first by the anaesthetic effect of the product)
Conjunctivitis may occur when EMLA is applied near the eyes for patient undergoing facial laser treatments
True (extreme caution should be exercised in this area because the alkalinity of the EMLA product can result in a chemical burn, the symptoms of which may be masked at first by the anaesthetic effect of the product)
G6PD deficiency is a relative contraindication to EMLA use
True (risk of Prilocaine-induced methaemoglobinaemia)
Significant cardiac disease is a relative contraindication to EMLA use
True (cardiovascular toxicity with the amides and esters)
Signifance hepatic disease is a relative contraindication to EMLA use
True (both lignocaine and prilocaine are metabolised in the liver by Cytochrome P450 enzymes)
EMLA is classified as pregnancy category B
True
The following analgesic drugs may increase the risk of methaemoglobinaemia especially when used with EMLA:
(1) acetaminophen
(2) acetanilid
(3) phenacetin
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
The following anaesthetic drugs may increase the risk of methaemoglobinaemia especially when used with EMLA:
(1) benzocaine (ester)
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
The following anti-convulsants drugs may increase the risk of methaemoglobinaemia especially when used with EMLA:
(1) phenytoin
(2) phenobarbital
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
The following antimalarial drugs may increase the risk of methaemoglobinaemia especially when used with EMLA:
(1) chloroquine
(2) hydroxychloroquine
(3) pamaquine
(4) primaquine
(5) quinine
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
The following nitrates/related drugs may increase the risk of methaemoglobinaemia especially when used with EMLA:
(1) nitrates and nitrites
(2) nitrofurantoin
(3) nitroglycerin
(4) nitroprusside
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
The following sulfonamides/sulfones drugs may increase the risk of methaemoglobinaemia especially when used with EMLA:
(1) dapsone
(2) sulfamethoxazole
(3) trimethoprim/sulfamethoxazole
True (methaemoglobinaemia is a unique adverse effect from Prilocaine within EMLA cream)
Topical lignocaine is used primarily to treat pain or pruritus
True
EMLA (lignocaine/Prilocaine) is more effective than TAC (Tetracaine/adrenaline/cocaine) when used as anaesthesia for laceration repair in children
True
A 5% Lignocaine patch is FDA approved for postherpetic neuralgia
True
Topical benzocaine (ester) is available in multiple formulations for skin an mucosal application for the temporary relief of pain and itching associated with burns, insect bites, and minor skin irritation
True
Topical benzocaine (ester) is a potent sensitiser more Lilley to induce allergy of applied to and area of concomitant dermatitis, broken or fissured skin
True
Patients allergic to topical benzocaine (ester) may cross-react with other ester local anaesthetics as supported by patch testing data
True (delayed type IV hypersensitivity, never been associated with immediate IgE type hypersensitivity leading to anaphylaxis although it is prudent to avoid giving systemic local anaesthetics to patients with a topical sensitivity to an agent in the same class)
Topical benzocaine has also been associated with methaemoglobinaemia in paediatric patients
True (similar to Prilocaine)
Topical Dyclonine (ketone) is used for:
(1) temporary relief of pain and itching associated with post-operative wounds
(2) mucosal anaesthetic before endoscopic procedures
True
Allergic contact dermatitis to topical Dyclonine (ketone) has been reported
True
Topical Pramoxine (ether) is commonly used as an antipruritic agent
True
Topical Dibucaine (amide) is commonly used in haemorrhoidal preparations
True
Adrenaline is most often used in dermatology as a vasoconstrictor injected with a local anaesthetic
True
Adrenaline prolongs the effect of the local anaesthetic
True
Adrenaline reduces the systemic absorption of the local anaesthetic
True
Adrenaline aids in haemostasis
True
Adrenaline is an endogenous catecholamine produced by the adrenal medulla
True
Adrenaline is synthesised in the body by tyrosine
True
Although adrenaline is both an alpha and beta adrenergic agonist, it is the alpha-adrenergic properties that cause vasoconstriction
True
Alpha-adrenergic = vasoconstriction (increase systemic vascular resistance and thereby increasing blood pressure)
Beta1-adrenergic = increase heart rate and cardiac contractility (increase cardiac output)
Beta2-adrenergic = bronchodilation
When given subcutaneously, the maximum vasoconstrictive effect of adrenaline takes place within 7-15 mins and a 60 mins duration of action
True
Adrenaline is rapidly inactivated in tissue primarily by enzymatic transformation to metadrenaline or normetadrenaline which are then conjugated in the liver and excreted in the kidneys
True (also undergoes direct degradation in the liver by MAO and catechol O-methyltransferase) - all these metabolic pathways results in production of vanillylmandelic acid in the urine
Adrenaline is more effective as a vasoconstrictor when used with lignocaine than with Bupivacaine or Mepivacaine because these latter 2 agents already have a delayed onset of action due to higher protein binding/lipophilicity
True
Adrenaline is FDA approved as a haemostatic agent
True
Adrenaline is FDA approved to prolong the action of local anaesthetics
True
Adrenaline is FDA approved to treat acute hypersensitivity reactions such as anaphylaxis and anaphylactoid reactions due to drugs or insect stings
True
Adrenaline is absolutely contraindicated in patients with sensitivity to sodium metabisulphite
True
Adrenaline is absolutely contraindicated in patients with phaeochromocytoma due to risk of hypertension
True
Adrenaline may cause palpitations (cardiac effects)
True (beta-adrenergic effect)
Adrenaline may cause dysrhythmias (cardiac effect)
True (beta adrenergic effect)
Adrenaline may cause hypertension (cardiac effect)
True (alpha and beta adrenergic effect)
Patients with IHD are more susceptible to dysrhythmias and compromised coronary blood flow from adrenaline owing to tachycardia and increased cardiac output
True (adrenaline relatively contraindicated in patients with cardiac disease)
Healthy patients = 50 mL of 1:100 000 adrenaline
Heart disease = 20 mL of 1:100 000 adrenaline
Severe heart disease = 4 mL of 1:100 000 adrenaline
Adrenaline may cause restlessness, tremor and headache (CNS effects)
True
Adrenaline may cause hyperglycaemia leading to lactic acidosis in patients with diabetes (endocrinologic effects)
True
Patients with poorly controlled hyperthyroidism are at risk of hypertension when treated with adrenaline
True
Adrenaline is relatively contraindicated in angle-closure glaucoma
True (adrenaline has sympathomimetic effects)
Lignocaine with adrenaline in reasonably conservative anaesthesia volumes may generally be used safely in the ears, nose and penis as these sites have excellent collateral flow
True (traditionally taught that adrenaline is not to be used in these areas as the vasoconstrictive effects may compromise circulation)
Lignocaine with adrenaline may be used safely in small volumes for infiltrative local analgesia of fingers and toes in patients who do not have vascular compromise
True (no evidence supporting the dogma that infiltrative analgesia and blocks produce digital necrosis)
Use of adrenaline in anaesthetics is generally safe in skin grafts, although plain lignocaine can be considered for patients who are likely to have compromised vasculature requiring these grafts
True
Malignancy hypertension has occurred in patients on non-cardioselective beta-blockers such as propanolol after receiving adrenaline infiltrative anaesthetic
True (thought to be due to alpha-adrenergic stimulation of peripheral vascular receptors from adrenaline is causing the vasoconstriction, while the beta2-adrenergic receptors which normally oppose their action are blocked by the propanolol) - although the infrequency nature of the occurrence with low doses of adrenaline in dermatologic surgery makes discontinuing these beta-blockers unnecessary
TCA (amitriptyline, imipramine) can enhance the sympathomimetic adverse cardiac effects of adrenaline (tachycardia and palpitations) as co-administration potentiates the anti-cholinergic effects on the heart
True
Antihistamines (chlorpheniramine, diphenhydramine) can enhance the sympathomimetic adverse cardiac effects of adrenaline (tachycardia and palpitations)
True
Thyroid replacement (thyroxine) can enhance the sympathomimetic adverse cardiac effects of adrenaline (tachycardia and palpitations)
True
Digoxin can enhance the sympathomimetic adverse cardiac effects of adrenaline (tachycardia and palpitations)
True
Quinidine can enhance the sympathomimetic adverse cardiac effects of adrenaline (tachycardia and palpitations)
True
Antipsychotic agents (haloperidol) can reverse the sympathomimetic adverse cardiac effects of adrenaline
True
Adrenaline is used in dermatologic surgery to maximise the anaesthetic effect and minimise the adverse effects of local anaesthetic agents
True
Capsaicin is a naturally occurring substance from hot chilli peppers
True
Topical capsaicin lotion/cream may be used as an adjuvant topical analgesic
True (effective only if applied consistently and frequently over time)
Topical capsaicin is FDA approved in the treatment of postherpetic neuralgia
True
Burning sensation is the main and most frequent adverse effect of topical capsaicin
True (80% of treated patients, the burning sensation diminishes with continued use over 1-2 weeks)
Pruritus is one of the adverse effects of topical capsaicin
True
Erythema is one of the adverse effects of topical capsaicin
True
Coughing is one of the adverse effects of topical capsaicin
True
Sneezing is one of the adverse effects of topical capsaicin
True
Patients using topical capsaicin should be cautioned to wash their hands after application to prevent inadvertent administration to uninvolved skin or mucous membranes
True
Superficial erosions is one of the adverse effects of topical capsaicin
True
Topical capsaicin may potentially delay wound healing if applied to abraded or broken skin
True (toxic to keratinocytes and fibroblasts in vitro)
Onset of analgesia from topical capsaicin is noted within 1-2 weeks with 3-5 X daily applications, however maximal analgesia may be delayed for 4-6 weeks
True
After each topical application of capsaicin, the analgesic effects last 3-6 hours
True
Injectable diphenhydramine (antihistamine) is an alternative local anaesthetic in lignocaine-sensitive (or other amide-sensitive) patients
True (mechanism of action similar to amide and ester anaesthetics which involve blockage of the sodium channels)
Diphenhydramine is more painful on injections than lignocaine injection for infiltrative anaesthetic, but is as effective as lignocaine in producing local anaesthesia
True
Diphenhydramine (antihistamine) infiltrative anaesthetic can cause somnolence
True (crosses the blood brain barrier as with the other sedating first generation antihistamines)
The most serious potential adverse effect of injectable diphenhydramine is tissue irritancy causing tissue necrosis, including digital necrosis resulting in amputation
True (these cases were associated with the higher dose 5% diphenhydramine and could be dose related, it may prove useful to use the 1% dose and avoid injection into areas where collateral circulation may be limited)
Diphenhydramine (antihistamine) may be used as as injectable anaesthetic and a topical anesthetic
True
Topical diphenhydramine (antihistamine) has been marketed for temporary relief of minor pain and pruritus
True
Topical diphenhydramine (antihistamine) is a potent sensitiser and can result in widespread dermatitis with subsequent systemic administration of diphenhydramine or related agents
True
Topical diphenhydramine (antihistamine) has been associated with severe systemic reactions in paediatric patients including death
True (increase body surface area in paediatric population resulting in diphenhydramine toxicity)
Application of topical diphenhydramine (antihistamine) to large areas of skin increases systemic absorption and may result in toxicity
True
Application of topical diphenhydramine (antihistamine) to skin with an impaired dermal barrier such as in eczema or varicella increases systemic absorption and may result in toxicity
True
Application of topical diphenhydramine (antihistamine) after bathing increases systemic absorption and may result in toxicity
True
