Methemoglobinemia associated with prilocaine use in neonatal circumcision

Topical anaesthesia for needle-related pain in newborn infants

BACKGROUND

Hospitalised newborn neonates frequently undergo painful invasive procedures that involve penetration of the skin and other tissues by a needle. One intervention that can be used prior to a needle insertion procedure is application of a topical local anaesthetic.

OBJECTIVES

To evaluate the efficacy and safety of topical anaesthetics such as amethocaine and EMLA in newborn term or preterm infants requiring an invasive procedure involving puncture of skin and other tissues with a needle.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Embase and CINAHL up to 15 May 2016; previous reviews including cross-references, abstracts, and conference proceedings. We contacted expert informants. We contacted authors directly to obtain additional data. We imposed no language restrictions.

SELECTION CRITERIA

Randomised, quasi-randomised controlled trials, and cluster and cross-over randomised trials that compared the topical anaesthetics amethocaine and eutectic mixture of local anaesthetics (EMLA) in terms of anaesthetic efficacy and safety in newborn term or preterm infants requiring an invasive procedure involving puncture of skin and other tissues with a needle DATA COLLECTION AND ANALYSIS: From the reports of the clinical trials we extracted data regarding clinical outcomes including pain, number of infants with methaemoglobin level 5% and above, number of needle prick attempts prior to successful needle-related procedure, crying, time taken to complete the procedure, episodes of apnoea, episodes of bradycardia, episodes of oxygen desaturation, neurodevelopmental disability and other adverse events.

MAIN RESULTS

Eight small randomised controlled trials met the inclusion criteria (n = 506). These studies compared either EMLA and placebo or amethocaine and placebo. No studies compared EMLA and amethocaine. We were unable to meta-analyse the outcome of pain due to differing outcome measures and methods of reporting. For EMLA, two individual studies reported a statistically significant reduction in pain compared to placebo during lumbar puncture and venepuncture. Three studies found no statistical difference between the groups during heel lancing. For amethocaine, three studies reported a statistically significant reduction in pain compared to placebo during venepuncture and one study reported a statistically significant reduction in pain compared to placebo during cannulation. One study reported no statistical difference between the two groups during intramuscular injection.One study reported no statistical difference between EMLA and the placebo group for successful venepuncture at first attempt. One study similarly reported no statistically significant difference between Amethocaine and the placebo group for successful cannulation at first attempt.Risk for local redness, swelling or blanching was significantly higher with EMLA (typical risk ratio (RR) 1.65, 95% confidence interval (CI) 1.24 to 2.19; typical risk difference (RD) 0.17, 95% CI 0.09 to 0.26; n = 272; number needed to treat for an additional harmful outcome (NNTH) 6, 95% CI 4 to 11; I² = 92% indicating considerable heterogeneity) although not for amethocaine (typical RR 2.11, 95% CI 0.72 to 6.16; typical RD 0.05, 95% CI -0.02 to 0.11, n = 221). These local skin reactions for EMLA and amethocaine were reported as short-lasting. Two studies reported no methaemoglobinaemia with single application of EMLA. The quality of the evidence on outcomes assessed according to GRADE was low to moderate.

AUTHORS' CONCLUSIONS

Overall, all the trials were small, and the effects of uncertain clinical significance. The evidence regarding the effectiveness or safety of the interventions studied is inadequate to support clinical recommendations. There has been no evaluation regarding any long-term effects of topical anaesthetics in newborn infants.High quality studies evaluating the efficacy and safety of topical anaesthetics such as amethocaine and EMLA for needle-related pain in newborn term or preterm infants are required. These studies should aim to determine efficacy of these topical anaesthetics and on homogenous groups of infants for gestational age. While there was no methaemoglobinaemia in the studies that reported methaemoglobin, the efficacy and safety of EMLA, especially in very preterm infants, and for repeated application, need to be further evaluated in future studies.

Blood concentration of prilocaine and lidocaine after the use of topical anesthesia (Oraqix® ) in lacerated wounds

BACKGROUND/AIM

Soft tissue injuries have been reported as being sutured using only topical anesthesia applied in the laceration wound. The objective of this study was to assess the pharmacokinetic profile of components of Oraqix^® (2.5% prilocaine and 2.5% lidocaine) when applied in a laceration as compared to intact skin application in the mouse.

MATERIALS AND METHODS

A total of 200 BALB/c male mice were used in this study. The mice were divided into three groups: group A: shaved and laceration group (80 mice); B: shaved and intact skin group (80 mice); and C: control group (shaved, no treatment; 40 mice) which underwent the same procedures but without application of Oraqix^® . Blood samples were collected over 90 min. Plasma sample analysis employing liquid chromatography coupled with the tandem mass spectrometric (LC-MS/MS) method was used to determine plasma concentrations of lidocaine and prilocaine. Pharmacokinetic analysis of mouse plasma concentrations was carried out by standard non-compartmental methods.

RESULTS

Absorption of both lidocaine and prilocaine was rapid. C_max and AUC values of lidocaine were significantly increased by fourfold and twofold, respectively, in lacerated mouse skin compared to intact skin. Similarly, prilocaine's C_max and AUC values were also increased by 2.5-fold and fourfold, respectively, in lacerated skin compared to intact skin.

CONCLUSION

When Oraqix^® was applied directly into the skin laceration, the plasma concentration of lidocaine and prilocaine was significantly increased as compared to when applied on intact skin. The present study, albeit in mice, indicates that the plasma levels of lidocaine and prilocaine can reach very high levels when the thermosetting gel Oraqix^® is placed directly in wounds.

A pharmacokinetic study of a topical anesthetic (EMLA® ) in mouse soft tissue laceration

The use of topical anesthesia instead of injection of local anesthetics for managing soft tissue lacerations in the emergency situations may be a relief for both patients and surgeons. Topical anesthesia in the form of a cream eutectic mixture of local anesthetics (EMLA®) containing 2.5% lidocaine and 2.5% prilocaine has been reported as an efficient anesthetic on skin before venipuncture anesthesia and as an alternative to injection anesthesia in some minor surgery situations. The aim of this study was to compare the pharmacokinetics of EMLA® when applied in a laceration with topical skin application in the mouse. A total of 120 Albino Laboratory-bred strain mouse (BALB-c) male mice were divided into three groups with regard to application mode of EMLA®. Group A: with laceration, 48 mice; Group B: on intact shaved skin, 48 mice; Group C: control group (24 mice) with same procedures but without application of EMLA®. Blood levels were collected at 0, 10, 20, 30, 45, 60, 75, and 90 min post-EMLA® application. Plasma sample analysis was carried out by employing liquid chromatography coupled with tandem mass spectrometric (LC-MS/MS) method, and the pharmacokinetic analysis of the mouse plasma samples was estimated by standard non-compartmental methods. The pharmacokinetic parameters of lidocaine and prilocaine were significantly altered following EMLA® application to lacerated mouse skin in contrast to intact skin. The absorption of lidocaine and prilocaine was rapid following application of EMLA® to lacerated and intact mouse skin. Maximum drug plasma concentration (C(max) ) and area under the drug plasma concentration-time curve (AUC) values of lidocaine were significantly increased by 448.6% and 161.5%, respectively, following application of EMLA to lacerated mouse skin in comparison with intact mouse skin. Similarly, prilocaine's C(max) and AUC values were also increased by 384% and 265.7%, respectively, following EMLA application to lacerated mouse skin, in contrast to intact skin. Further pharmacokinetic studies on different carriers of lidocaine/prilocaine are warranted before any firm conclusions for the clinic can be drawn.

Randomized trial of novel tetracaine patch to provide local anaesthesia in neonates undergoing venepuncture

BACKGROUND

Procedures such as venepuncture or heel prick are painful and may cause considerable stress to newborn infants. Topical local anaesthetics are effective for venepuncture but need to be applied for at least 60 min and the delivered dose will vary. We assessed a novel tetracaine-based self-adhesive patch in providing controlled local anaesthesia before venepuncture.

METHODS

A placebo-controlled, double-blind trial was conducted using a tetracaine patch formulated from hydroxypropylcellulose discs (0.283 cm(2)) containing tetracaine (1 mg x cm(-2)) surrounded by a low tack pressure-sensitive adhesive backing layer. Thirty-two newborn infants of gestation 32-42 weeks (median 36 weeks), aged 3-18 days (median 6 days) were randomized to receive a tetracaine-containing patch or a placebo device applied to the dorsum of the hand 30 min before venepuncture to obtain blood samples. Pain was assessed in response to needle insertion using a validated adaptation of the neonatal facial coding score (NFCS) and the presence of crying.

RESULTS

Of 15 tetracaine-treated neonates, 14 (93%) presented little or no pain in response to the procedure compared with six of 17 (35%) who had the placebo patch applied (P=0.01).

CONCLUSIONS

The tetracaine patch produced effective pain relief during the venepuncture procedure in both term and pre-term infants. There were no adverse effects, either local or systemic.

Toxic Methemoglobinemia Complicating Transesophageal Echocardiography

We describe the case of a patient with acute methemoglobinemia after topical oropharyngeal anesthesia with benzocaine spray.

Adverse drug interactions in dental practice: interactions associated with local anesthetics, sedatives and anxiolytics. Part IV of a series

BACKGROUND

This article is the fourth in a five-part series based on a 1998 International Association for Dental Research symposium entitled "Adverse Drug Interactions in Dentistry: Separating the Myths From the Facts." The symposium evaluated the significance of various drug interactions associated with dental therapeutics.

METHODS

Local anesthesia and preoperative oral sedative/anxiolytic therapy often are indicated for routine oral surgery and restorative dentistry. The author conducted a literature review of the drug interactions associated with the use of local anesthetics and sedatives. The quality of the information used to document these interactions and the severity of the possible adverse outcome were assessed using a significance rating scale for dental drug interactions.

RESULTS

Many of the frequently described drug interactions were found to be poorly documented in the dental and medical literature. Others were determined not to be relevant to current dental practice. The use of local anesthetics, sedatives or anxiolytic agents in combination with other central nervous system depressant agents or in combination with drugs that inhibit their metabolism was associated with a few serious adverse drug interactions or complications.

CONCLUSIONS

The adverse drug interactions associated with the use of local anesthetics and oral sedative/anxiolytic agents in general practice vary in significance. An understanding of possible adverse drug interactions in dentistry may help practitioners avoid and prevent these complications.