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PubMedDate not supplied

Allergy to local anesthetics in dentistry. Myth or reality?

BACKGROUND: Local anesthetics are drugs frequently used in dentistry. Although they are usually well-tolerated drugs, sometimes, they can cause adverse reactions of different kinds and severity. True incidence of local anesthetics' allergic reactions is unknown. OBJECTIVES: To evaluate the incidence of immediate adverse events in subjects who required local anesthetic injection to receive dental treatment; to assess the incidence of anaphylactic allergic reactions among those recorded as adverse events; to analyze the relationship between these patients' atopic antecedents and documented allergic reactions. MATERIAL AND METHODS: A prospective, open-label, non-comparative study including a total of 5,018 subjects who received local anesthetics during dental treatment, despite their age, was carried on in 7 either private or public odontological assistance centers. All the reactions that could appear during the first hour following the anesthetic act were assessed. RESULTS: Twenty-five adverse reactions were diagnosed, representing 0.5% of the studied population. None of them was due to an allergic cause. Most of them (22/25) were mild, quickly reversible, psychogenic or vasovagal reactions. One of the cases was related to defects of the anesthetic technique. The remaining two cases, which were initially considered as possibly due to an allergic cause, were discarded after being studied with skin and dose provocative challenge tests with the anesthetic. CONCLUSION: The allergic reactions to the local anesthetics are very rare and most of the adverse reactions are psychogenic/vasovagal. These facts should be known by the physician and by the dentist in order to minimize the frequent fears and "myths" about the use of local anesthetics at the dentist office.

Adolescent↗
PubMed2002

Local anesthetics for facial plastic procedures.

The use of local anesthetic in facial plastic surgical procedures is well established as an effective and safe mode of anesthesia delivery. Local infiltration of anesthesia may be used alone for minor surgical procedures, or it may be used with general anesthesia or intravenous sedation and analgesia for more complex, lengthy procedures. When considered independently, the use of local anesthetic agents has undeniable limitations. Local anesthetics can cause toxicity and side effects. Injection of local anesthetics for subcutaneous infiltration frequently is painful until sensory anesthesia occurs. Local anesthetics have limited efficacy with respect to the intensity and duration of sensory blockade that can be achieved. In some situations, use of local anesthesia with the maintenance of an awake patient also may be undesirable for the surgeon and impractical for the patient. Despite these shortcomings, local anesthetics are fundamentally ideal for use in facial plastic surgery.

Anesthetics, Local↗
PubMed2003

[Local anesthetics. Differences and similarities in the "-cains"].

Local anesthetics provoke reversible blockade of nerves by interaction with sodium channels in membranes of nerves. The uncharged molecular configuration of the local anesthetic penetrates the membrane from the outside and the charged configuration then interacts with the sodium channel from the inside. The potency of a local anesthetic is determined mainly by lipid solubility, the time of onset by the pK(a) of the substance and the duration of action by protein binding. Local anesthetic molecules consist of a hydrophilic tertiary amine and a lipophilic aromatic system combined by an ester or amide linkage. Local anesthetics may therefore be classified as aminoester or aminoamide compounds. Aminoesters are hydrolysed by plasmacholinesterase whereas aminoamides undergo metabolisation in the liver. Aminoamides cause fewer allergic reactions. Local anesthetics show dose-dependent CNS and cardiac toxicity. Reports of toxicity, mainly involving bupivacaine and etidocaine initiated the development of ropivacaine which is the first aminoamide marketed as a pure S-enantiomer. Recently introduced was levo-bupivacaine, the S-enantiomer of bupivacaine.

Anesthetics, Local↗
PubMed1984

Adsorption of local anesthetics on phospholipid membranes.

In order to elucidate various types of adsorption modes of local anesthetics in membranes, a study of local anesthetic adsorption on lipid membranes was made by measuring electrophoretic mobility of phospholipid vesicles in the presence of local anesthetics of various concentrations in the vesicle suspension solution. The amounts of local anesthetics to be adsorbed on the membrane surface were deduced from the electrophoretic mobility of a phosphatidylcholine vesicle at various concentrations of the cationic form of local anesthetics. The order of surface adsorption of local anesthetic was dibucaine greater than tetracaine greater than procaine. A surface partition coefficient, Ks = 1/ACs, was introduced, where A is the membrane surface area per local anesthetic molecule adsorbed and Cs the surface concentration of local anesthetics. The amounts of local anesthetic adsorbed on phosphatidylserine membrane were much greater than that of the phosphatidylcholine membrane. It was deduced that the major factor for this large adsorption was due to the enhancement of cationic forms of local anesthetic concentrations at the charged membrane surface. Divalent cations inhibited such surface adsorption of local anesthetics by reducing surface concentrations of local anesthetics where the surface potential of the negatively charged membrane surface was influenced by the presence of divalent cations in the solution as well as by the reduction of fixed surface charges due to divalent cation binding. Some association modes of local anesthetics on nerve membranes are discussed with the results obtained in the above adsorption study.

Adsorption↗
PubMed1993

Effect of a topical anesthetic cream (EMLA) in reducing pain caused by infiltration of local anesthetic in eyelid surgery.

EMLA (eutectic mixture of local anesthetics) cream is a topical formulation of a mixture of lidocaine and prilocaine. It has been used to achieve local analgesia after application under an occlusive dressing. We carried out a double-blind randomized controlled clinical trial to assess the effect of 5% EMLA (25 mg/mL of lidocaine and of prilocaine) in reducing the pain caused by infiltration of local anesthetic in eyelid surgery. Pain was assessed by means of a modified visual analogue scale ranging from 0 (no pain) to 10 (excruciating pain) in 25 consecutive patients (average age 65 years) undergoing bilateral eyelid surgery. Clinical significance was defined as a difference in pain scores of 3 or more between EMLA and placebo. The mean pain scores for EMLA and placebo were 3.1 and 4.0 respectively, a nonsignificant difference. The EMLA preparation was found not to be clinically effective in reducing pain caused by infiltration of local anesthetic in eyelid surgery.

Aged↗
PubMed1995

Effects of verapamil on spinal anesthesia with local anesthetics.

The primary mode of action of local anesthetics is through sodium channel and axonal conduction blockade. Local anesthetics also have extensive effects on presynaptic calcium channels that must function to stimulate the release of neurotransmitters. Thus, interference with calcium channel conductance may enhance spinal anesthesia with local anesthetics. The present study was designed to investigate the effects of the intrathecal calcium channel blocker, verapamil, on the spinal anesthesia from lidocaine and tetracaine. Male Sprague-Dawley rats were chronically implanted with lumbar intrathecal catheters. Tail-flick (TF) and mechanical paw pressure (MPP) tests were used to assess thermal and mechanical nociceptive threshold, respectively. Motor function was assessed using a modified Langerman's scale. Intrathecal lidocaine or tetracaine alone showed the prolongation of TF latency, the increase of MPP threshold, and the increase in motor function scale in a time- and dose-dependent manner. Although intrathecal verapamil alone demonstrated neither sensory nor motor block at the doses used (50-200 micrograms), the combination of lidocaine (20, 50, 100, or 200 micrograms) or tetracaine (10, 20, 50, or 100 micrograms) and verapamil (50 micrograms) produced the more potent and prolonged antinociception and motor block when compared with local anesthetics alone. We interpreted these results to indicate that the intrathecal calcium channel blocker, verapamil, potentiates spinal anesthesia with local anesthetics.

Anesthesia, Spinal↗
PubMed1997

Structure-affinity relationships and stereospecificity of several homologous series of local anesthetics for the beta2-adrenergic receptor.

UNLABELLED: Local anesthetics inhibit binding of ligands to beta2-adrenergic receptors (beta2ARs), and, as a consequence, inhibit intracellular cAMP production. We hypothesized that among homologous local anesthetics, their avidity at inhibiting binding of tritiated dihydroalprenolol (3H-DHA) to beta2ARs would increase with increasing length of alkyl substituents and would demonstrate stereospecificity. Specific binding of 3H-DHA to human beta2ARs was assayed in the presence of six different members of the 1-alkyl-2,6-pipecoloxylidide class of local anesthetics (including mepivacaine, ropivacaine, and bupivacaine), the R(+) and S(-) bupivacaine enantiomers, lidocaine, prilocaine, etidocaine, procaine, and tetracaine. Avidity of binding to beta2ARs increased with increasing length of the alkyl chain (pKi values = 2.4, 3.6, 4.3, 4.1, 4.1, 5.9 for the methyl [mepivacaine], ethyl, S(-)propyl [ropivacaine], butyl [bupivacaine], pentyl, and octyl derivatives, respectively). We found no evidence for bupivacaine stereospecificity (pKi values = 4.3 and 4.9 for the S(-) and R(+) isomers, respectively). Other amide and ester local anesthetics also showed increasing potency with increasing length of alkyl substituents (pKi values = 3.6, 3.8, and 4.3 for lidocaine, prilocaine, and etidocaine; 4.2 and 5.6 for procaine and tetracaine, respectively). The correlation between increased inhibition of beta2AR binding and alkyl chain length resembles the correlation between local anesthetic potency at nerve block and increased alkyl chain length. The lack of clear stereospecificity is consistent with the relatively low potency these agents demonstrate at inhibition of beta2AR binding. Finally, the relatively potent inhibition of beta2ARs by etidocaine, tetracaine, and bupivacaine suggests that their propensity for cardiovascular depression after accidental intravenous overdose could result from beta2AR or beta1AR blockade and inhibition of cAMP production. IMPLICATIONS: Local anesthetics demonstrate a rank order of avidity for displacing ligands from beta2-adrenergic receptors such that larger molecules displace ligands at lower concentrations than smaller local anesthetic molecules. This relationship between molecular size and receptor avidity could explain the greater propensity for cardiovascular toxicity of relatively large local anesthetics such as bupivacaine.

Adrenergic beta-2 Receptor Antagonists↗
PubMed1984

Studies on rabbit corneal permeability of local anesthetics (I).

To elucidate the pharmacokinetics of local anesthetics with respect to corneal permeability in the rabbit, we examined the relationship between the corneal permeability velocities of three agents, cocaine X HCl, procaine X HCl and tetracaine X HCl and corneal hydration. The corneal permeability velocity constants (k) of these three ester-type local anesthetics were approximately 0.5-6.0 X 10(-6) cm/sec and the membrane permeability constants of these agents were approximately 0.5-4.0 X 10(-7) cm2/sec, whereas the rabbit corneal hydration values were 3.2-4.2. Tetracaine X HCl with the strongest topical anesthetic action showed the greatest corneal hydration and the smallest corneal permeability velocity constant among these local anesthetics. Rabbit corneal permeability decreased with increasing molecular length of the agents. Permeability of these local anesthetics in the rabbit cornea appears to result from passive transport. As corneal hydration values and the corneal permeability constant increased with greater topical anesthetic activity, it appears that the degree of inhibition of Na+-K+ ATPase activity is associated with the order of topical anesthetic activity in a similar manner as general anesthetics.

Anesthetics, Local↗
PubMed2003

[Tissue toxicity of local anesthetics. An in vivo trial].

AIM: Local anesthetics are often administered intra-articularly after knee surgery. The aim of this study was to determine differences in irritancy of local anesthetics in an in vivo test performed on the chorioallantoic membrane of hen's eggs (HET-CAM test) to evaluate the specific irritation score. METHOD: After incubation for 9 days, the chorioallantoic membrane was prepared and then exposed to different local anesthetics (Naropin, Scandicain,Carbostesin,Xyloneural). RESULTS: We found no irritating values for the tested substances. No vascular injuries of the chorioallantoic membrane could be detected. Therefore, the irritation score was measured according to the standard protocol with an irritation score=0. CONCLUSION: Our results show that local anesthetics often used in clinics do not provoke severe vascular injuries as a sign of tissue toxicity. Therefore, the customary concentrations can be recommended for clinical use.

Allantois↗
PubMedDate not supplied

Preparation of pH-adjusted local anesthetics.

Characteristics of alkalinized local anesthetics are poorly described with regard to stability and precipitation. Current fixed-volume methods of alkalinization often result in unstable, precipitated solutions of unpredictable pH. We determined a stable, nonprecipitating, anesthetic mixture and used it in a randomized double-blind crossover study of 21 patients to evaluate alkalinized anesthetic solutions in reducing pain on injection. Our solution significantly reduced pain associated with retrobulbar injection (analysis of variance, P = .0362) but not that associated with Nadbath injection. Fixed-volume alkalinization is not recommended because complications can result with the use of precipitated anesthetics.

Anesthesia, Local↗