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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.55 no.2 Campinas Mar./Apr. 2005
Comparative study between botulin toxin and bupivacaine for triggering-points infiltration in chronic myofascial syndrome*
Estudio comparativo entre toxina botulínica y bupivacaína para infiltración de puntos-gatillo en síndrome miofascial crónica
Eduardo Keiichi Unno, M.D.I; Rioko Kimiko Sakata, TSA, M.D.II; Adriana Machado Issy, M.D.III
IEstagiário do Setor de Dor da Disciplina
de Anestesiologia, Dor e Terapia Intensiva da UNIFESP EPM
IIProfessora Adjunta e Responsável pelo Setor de Dor da Disciplina de Anestesiologia, Dor e Terapia Intensiva da UNIFESP EPM
IIIProfessora Adjunta da Disciplina de Anestesiologia, Dor e Terapia Intensiva da UNIFESP EPM
BACKGROUND AND OBJECTIVES: There are controversies
about the efficacy of botulin toxin as compared to local anesthetics for triggering-points
infiltration. This study aimed at comparing the analgesic effect of botulin
toxin and bupivacaine for triggering-points infiltration in chronic myofascial
METHODS: Participated in this study 20 patients divided in two groups. G1 patients (n = 10) received 25U botulin toxin and G2 patients (n = 10) received 0.25% bupivacaine in one to three triggering-points, being 0.5 mL per point. Patients were weekly evaluated for 8 weeks. Orphenadrine (35 mg) and dipirone (300 mg) were associated every 8 hours and patients were submitted to transcutaneous electrical stimulation twice a week during 1 hour. Pain intensity was evaluated through verbal numeric scale and quality of analgesia was evaluated by patients in moments zero (before injection), 30 minutes after, and at 1, 2, 3, 4, 5, 6, 7 and 8 weeks. Results were submitted to statistical analysis (Mann-Whitney and Fisher Exact tests).
RESULTS: After 30 minutes, 1 and 4 weeks, pain intensity was lower for G1 as compared to G2. After 2, 3, 5, 7 and 8 weeks, there was no significant difference between groups. Quality of analgesia was considered better by G1 patients as compared to G2, except after 2 weeks.
CONCLUSIONS: Analgesic effect was better with botulin toxin (25U) as compared to 0.25% bupivacaine for triggering-points infiltration.
Key words: ANESTHETICS, Local: bupivacaine; DRUGS: botulin toxin A; ANESTHETIC TECHNIQUES: triggering-points infiltration
JUSTIFICATIVA Y OBJETIVOS: Existen controversias
sobre la eficacia de la toxina botulínica con relación al anestésico local para
infiltración de puntos-gatillo. El objetivo de este estudio es comparar el efecto
analgésico de la toxina botulínica con el de la bupivacaína, para infiltración
en puntos-gatillo de síndrome miofascial crónica.
MÉTODO: Fueron evaluados 20 pacientes, divididos en dos grupos. Los pacientes del G1 (n = 10) recibieron 25U de toxina botulínica y los del G2 (n = 10), bupivacaína a 0,25%, de un a tres puntos-gatillo, siendo 0,5 mL por punto. Los pacientes fueron evaluados semanalmente, durante 8 semanas. Fueron asociados 35 mg de orfenadrina, y 300 mg de dipirona, a cada 8 horas, los pacientes fueron sometidos a estimulación eléctrica transcutánea, dos veces por semana, durante 1 hora por sesión. La intensidad del dolor fue evaluada a través de la escala numérica verbal y la calidad de la analgesia, por el paciente, en los momentos cero (antes de la inyección), y después de 30 minutos, 1, 2, 3, 4, 5, 6, 7 y 8 semanas. Los resultados fueron sometidos al análisis estadístico (Mann-Whitney y Exacto de Fisher).
RESULTADOS: Después de 30 minutos de la aplicación y con 1 y 4 semanas, la intensidad del dolor en el G1 fue menor que en el G2. Después de 2, 3, 5, 7 y 8 semanas de la infiltración, no hubo diferencia significativa entre los grupos. La calidad de la analgesia fue considerada mejor por los pacientes del G1 que del G2, excepto después de 2 semanas.
CONCLUSIONES: El efecto analgésico fue mejor con toxina botulínica (25U) que con bupivacaína a 0,25% para infiltración de puntos-gatillo.
Chronic myofascial syndrome is very common and is present in 30% to 50% of patients referred to Pain Clinics. It may be acute or chronic, isolated or associated to other painful syndromes and very often pain is severe and difficult to relief.
It is a regional muscle pain characterized by palpable tense muscle bands in which severely painful points are identified, called triggering-points which, when stimulated by digital palpation, cause severe local pain and distant referred pain 1,2.
Triggering-points may be found as nodes and are developed after trauma, excessive use or prolonged muscle spasm. They are caused by dynamic (trauma, excessive use) or static (postural) overloads of daily and occupational activities. Location of these nodes is similar in the same muscles of different individuals. These nodes may be found in painless individuals and are called latent triggering-points.
There are several treatments for myofascial syndrome. For patients not obtaining analgesia with anti-inflammatory drugs, muscular relaxants, electric stimulation or acupuncture among other approaches 3, botulin toxin injection in triggering-points may be an option.
Botulin toxin type A is a neurotoxin blocking acetylcholine release from cholinergic nervous terminations without changing neural conduction or acetylcholine synthesis and storage 4-10.
There are three stages for botulin toxin effects. Initially, botulin toxin is irreversibly linked to pre-synaptic membrane receptors of terminal endplate. Then, there is endocytosis with release of part of the molecule in nervous terminations cytoplasm, and at the end, there is functional muscular denervation determining selective muscle contraction.
Botulin toxin does not change acetylcholine synthesis and storage or electrical signals conduction. Botulin toxin injection in adequate dose and muscle location promotes partial denervation and decreased contracture without total paralysis.
Botulin toxin type A is a biological agent obtained in laboratory and is a stable, dried frozen crystalline solution associated to human albumin and used after dilution in saline. It is measured in biological units (U) defined by total lethal-50 dose (DL50) 11.
Botulin toxin action is observed in some days to 2 weeks and lasts for 6 weeks to 6 months (mean of 3 to 4 months). During more intense effect, muscle atrophy and fiber changes are observed at histological exam. During recovery, sprouts are formed with re-enervation and formation of new smaller endplates.
Primary risk is muscle weakness, which may be present after injection of a dose above the indication for a certain muscle. Total excessive dose may also promote weakness of neighbor muscles, however with adequate doses injected in adequate sites, complications are very uncommon.
There are no studies checking whether botulin toxin promotes better results as compared to local anesthetics.
Our study aimed at comparing the analgesic effect of botulin toxin and bupivacaine in triggering-points of chronic myofascial syndrome patients.
After Hospital São Paulo, Universidade Federal de São Paulo Research Ethics Committee approval and their informed consent, participated in this study 20 adult patients of both genders, with myofascial syndrome and moderate or severe chronic pain. Patients were divided in two equal groups.
Exclusion criteria were patients under opioids in the last 24 hours, with local infection or coagulopaties, those under anticoagulants, hypersensitive to albumin and pregnant women.
Group 1 patients (n = 10) received 25 U botulin toxin in saline. Group 2 patients (n = 10) received 0.25% bupivacaine without vasoconstrictor. Infiltration was identically performed in one to three triggering-points in both groups, being 0.5 mL per point. Patients were weekly evaluated for 8 weeks. During the study, 35 mg orphenadrine and 300 mg dipirone were associated every 8 hours. Patients were also submitted to transcutaneous electric stimulation twice a week for 1 hour.
Pain intensity was evaluated by verbal numeric scale where zero meant no pain and 10 the most severe pain ever experienced. Quality of analgesia was evaluated according to patients' reports through 4 descriptors (E = excellent; G = good; R = regular; P = poor). Pain intensity and quality of analgesia were evaluated in moments zero (before injection), 30 minutes after injection and at 1, 2, 3, 4, 5, 6, 7, and 8 weeks.
Botulin toxin analgesic effect and possible side effects were recorded. Results were submitted to statistical analysis (Mann-Whitney and Fisher Exact tests, p < 0.05).
Groups were similar in age, gender and body mass index (BMI). Mean age was 41.5 years for G1 and 51.3 years for G2. In both groups, two patients were male and 8 female. Mean BMI was 24.8 for G1 and 26.1 for G2.
Pain intensity before infiltration was similar for both groups (Table I). After 30 minutes, 1 and 4 weeks, pain intensity in G1 was lower as compared to G2, with statistically significant difference (Table I). After 2, 3, 5, 6, 7 and 8 weeks, there were no statistically significant differences between groups in pain intensity (Table I) (Mann-Whitney test).
Analgesia was considered better by G1 patients as compared to G2, with statistically significant difference, except after 2 weeks (Table II) (Fisher Exact test).
There has been better analgesic effect in G1 until the 8th week (M8) during last evaluation. No side effect was observed in both groups during the study period.
Different treatments are used to relieve myofascial syndrome pain and many drugs have been evaluated for triggering-points infiltration. Local anesthetics are the most common, however since they have short duration, notwithstanding the adequate effect there might be pain recurrence.
Botulin toxin type A infiltration is being used with satisfactory analgesic results 6,8,12-15.
Studies have shown that safe botulin toxin dose to treat myofascial syndrome is 4 U/kg 16, but our study has used lower doses. Dose was 25 U regardless of weight, however the lightest patient weighed 41 kg.
Botulin toxin acts directly on the affected muscle, promoting relaxation and, as a consequence, decreasing pain. When pain intensity is decreased, patients are able to perform physical exercises needed for their recovery and quality of life improvement 13.
It is important to remind that during the period in which patients are under drug effects, rehabilitation and muscle re-balance processes should be intensified with physical measures to obtain more effective treatment 11,13.
Our study has observed that botulin toxin type A is more effective as compared to local anesthetics in triggering-points infiltration to treat myofascial syndrome. Although with no statistically significant difference in moments M2, M3, M5, M6, M7, M8, pain intensity scores were lower with botulin toxin as compared to local anesthetics.
Local anesthetics for triggering-points infiltration are a good option, but botulin toxin type A may be an alternative, especially for patients with long lasting myofascial syndrome who achieve adequate pain relief after local anesthetic infiltration but who have pain recurrence. Prolonged pain relief is important because it relaxes muscles for enough time for patients' recovery.
Although being limited by its high cost, botulin toxin A may be cost-effective for some patients because fewer applications are needed (it lasts for up to 6 months). Local anesthetics may require several infiltrations with local discomfort, in addition to the need of several medical visits, which also generates costs.
In the conditions of this clinical study, analgesic effects were better with botulin toxin (25 U) as compared to 0.25% bupivacaine for triggering-points infiltration.
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Submitted for publication May 31, 2004
Accepted for publication November 23, 2004
* Received from Disciplina de Anestesiologia, Dor e Terapia Intensiva da Universidade Federal de São Paulo, Escola Paulista de Medicina (UNIFESP EPM), São Paulo, SP