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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Rev. Bras. Anestesiol. vol.51 no.4 Campinas  2001 



Betanecol in the treatment of spinal morphine-induced urinary retention*


Betanecol no tratamento da retenção urinária provocada pela morfina subaracnóidea


Betanecol en el tratamiento de la retención urinaria provocada por la morfina subaracnóidea



Clóvis José da Silva Borges, M.D.I; Sávio José Romuando de Araújo, M.D.II

IAnestesiologista do Hospital Universitário Lauro Wanderley da UFPB
IIME2 do CET/SBA Hospital Universitário Lauro Wanderley da UFPB





BACKGROUND AND OBJECTIVES: Morphine has been used in spinal blocks for postoperative analgesia due to its prolonged and intense analgesic potential. Even so, its side effects very often limit its use. Urinary retention is one of them.
METHODS: Of forty-seven patients submitted to surgical and obstetric procedures under spinal block with 0.1 mg morphine, 26 patients developed urinary retention (55.3%). When the classic treatment (micturition stimulation and local compresses) failed, fractionated doses of oral 12.5 mg betanecol were used at every hour, totaling 50 mg in 4 hours. After that period without appropriate response or if the patient presented intense vesical discomfort before the last dose, vesical catheterization would be performed or naloxone would be administered and the method was considered ineffective for those cases.
RESULTS: The conservative treatment failed in patients with urinary retention. However, betanecol in the doses standardized in our study, was effective in 14 patient (53.8%).
CONCLUSIONS: Betanecol can be a good coadjuvant for treating spinal morphine-induced urinary retention.

Key words: ANALGESICS, Opioids: morphine; ANESTHETIC TECHNIQUES, Regional: spinal block; COMPLICATIONS: urinary retention; DRUGS: betanecol


JUSTIFICATIVA E OBJETIVOS: A morfina tem sido utilizada nos bloqueios subaracnóideos para analgesia pós-operatória graças ao seu potencial analgésico prolongado e intenso. Porém, seus efeitos colaterais muitas vezes restringem seu uso. A retenção urinária é um deles. O objetivo deste estudo foi avaliar o emprego do betanecol para tratamento da retenção urinária causada pela morfina subaracnóidea, evitando assim a cateterização vesical do paciente.
MÉTODO: De quarenta e sete pacientes que foram submetidos a procedimentos cirúrgicos com técnica anestésica de bloqueios subaracnóideos nas clínicas cirúrgicas e obstétricas com administração de morfina na dose de 0,1 mg, 26 pacientes apresentaram retenção urinária (55,3%). Quando o tratamento clássico (estimulação miccional e compressas locais) não evoluiu com sucesso, foram utilizadas doses fracionadas de 12,5 mg de betanecol, por via oral a cada hora, totalizando 50 mg em 4 horas. Após esse período sem resposta adequada ou se o paciente apresentasse incômodo vesical intenso antes de completar a última dose da medicação, seria feita cateterização vesical ou o uso de naloxona, classificando o método como ineficaz nesses casos.
RESULTADOS:  Nos pacientes que apresentaram retenção urinária, o tratamento conservador não obteve sucesso. Porém administrando-se betanecol de acordo com a padronização das doses nesse estudo, o mesmo foi eficaz em 14 pacientes (53,8%).
CONCLUSÕES: O betanecol pode ser um bom coadjuvante no tratamento da retenção urinária provocada pela morfina subaracnóidea.

Unitermos: ANALGÉSICOS, Opióides: morfina; COMPLICAÇÕES: retenção urinária; DROGAS: betanecol; TÉCNICAS ANESTÉSICAS, Regional: subaracnóidea


JUSTIFICATIVA Y OBJETIVOS: La morfina ha sido utilizada en los bloqueos subaracnóideos para analgesia pós-operatoria gracias a su potencial analgésico prolongado e intenso. Más, sus efectos colaterales muchas veces restringen su uso. La retención urinaria es un deles. El objetivo de este estudio fue evaluar el empleo del betanecol para tratamiento de la retención urinaria causada por la morfina subaracnóidea, evitando así la cateterización vesical del paciente.
MÉTODO: De cuarenta y siete pacientes que fueron sometidos a procedimientos quirúrgicos con técnica anestésica de bloqueos subaracnóideos en las clínicas quirúrgicas y obstétricas con administración de morfina en la dosis de 0,1 mg, 26 pacientes presentaron retención urinaria (55,3%). Cuando el tratamiento clásico (estimulación miccional y compresas locales) no evolucionó con suceso, fueron utilizadas dosis fraccionadas de 12,5 mg de betanecol, por vía oral a cada hora, totalizando 50 mg en 4 horas. Después de ese período sin respuesta adecuada o si el paciente presentase incomodo vejical intenso antes de completar la última dosis de la medicación, seria hecha cateterización vejical o el uso de naloxona, clasificando el método como ineficaz en esos casos.
RESULTADOS: En los pacientes que presentaron retención urinaria, el tratamiento conservador no obtuvo suceso. Sin embargo administrándose betanecol de acuerdo con los padrones de las dosis en ese estudio, el mismo fue eficaz en 14 pacientes (53,8%).
CONCLUSIONES: El betanecol puede ser un buen coadyuvante en el tratamiento de la retención urinaria provocada por la morfina subaracnóidea.




Morphine in often used in spinal blocks. Its major advantage is prolonged postoperative analgesia (18 to 24 hours) due to its hydrophilic characteristic; however, as with any other drug, it is not free from side-effects. Urinary retention results from its action on spinal cord dorsal horn µ and k receptors, mainly on the gelatinous substance, inhibiting micturition reflex, increasing external urethral sphincter tonus and relaxing urethers vesical trigone1-3.

Current spinal morphine-induced urine retention treatments are a specific opioid antagonist or vesical catheterization1, but those methods have disadvantages because the first presents a dose-dependent antagonization of morphine’s analgesic effect and the latter poses a risk for urinary tract infection4.

Betanecol, a muscarinic agonist, stimulates the urinary tract, increases uretheral movements, contracts detrusor muscle, increases maximum voluntary micturition pressure and decreases vesical capacity, in addition to contracting the vesical trigone of bladder and relaxing external urethral sphincter2.

This study aimed at evaluating the efficacy of betanecol in treating spinal morphine-induced urine retention, thus preventing the antagonization of morphine’s analgesic effects and vesical catheterization.



After the Hospital Universitário Lauro Wanderley Research and Ethics Committee approval and their informed consent, participated in this study 47 patients of both genders, aged 15 to 65 years, physical status ASA I, II and III, exclusively submitted to surgical procedures under spinal block (inguinal hernias, Cesarean sections, hemorrhoidectomies and pilonidal cysts ressections), who were evaluated during the first 24 postoperative hours and informed about the importance of micturition stimulation. Patients with hyperthyroidism or hypotension history, vasomotor instability, epilepsy, Parkinson’s disease or submitted to previous vesical catheter were excluded from the study.

Patients were premedicated with oral diazepam (0.1 to 0.15 60 to 90 minutes before the procedure. Monitoring in the operating room consisted of cardioscope, non invasive blood pressure, pulse oximetry and a venous line with an 18 or 20G catheter in an upper limb for crystalloid and drug infusion. Patients were hydrated with 5 to 15 of crystalloids, according on surgery type and duration. Spinal morphine dose was standardized in 0.1 mg and local anesthesia was performed at L2-L3 or L3-L4 interspace with 15 to 20 mg hyperbaric bupivacaine and 25G or 27G Quincke needle. Patients developing urinary retention received the classic treatment of micturition stimulation and local compresses. In case of failure, oral fractionated doses of 12.5 mg betanecol were administered at every hour in a total of 50 mg in 4 hours. After this period and faced to an inadequate response, that is no spontaneous micturition or intense vesical discomfort before the last dose, patients were submitted to vesical catheterization or would receive naloxone being the method classified as ineffective. Adverse effects of the drug being studied were also evaluated.

Data were submitted to descriptive analysis.



Of 47 patients submitted to spinal block, 26 (55.3%) had urinary retention (Table I).

The period in which patients had more urinary retention was from 6 to 12 hours after surgery, with an incidence of 17 patients (65.4%), followed by 12 to 18 hours with 6 patients (23.1%) and from 0 to 6 hours with 3 patients (11.5%), while after the 18th hour no urinary retention was observed (Table II).

The conservative treatment failed with patients developing urinary retention. However, betanecol in standardized doses was effective in 14 patients or 53.8% (Table III).

In the postoperative period betanecol was effective in 3 patients from 0 to 6 hours with the best response after 6 hours (Table IV).

Drug efficacy was evaluated as a function of the time it took for spontaneous micturition, according to the dose used. Minimum dose to obtain a positive response was 25 mg and the highest effective dose initiate at 37.5 mg (Table V).



Quality in postoperative analgesia with few side-effects has been always looked for. Spinal morphine provides adequate analgesia but its side-effects limit its use.

Currently, with lower doses and especially with existing antagonists, it has become safer and with less undesirable effects.

This study aimed at finding a safe way to reduce morphine-induced urinary retention without affecting postoperative analgesia. So, we decided to administer betanecol to treat morphine-induced urinary retention because betanecol is a muscarinic cholinomimetic agent acting on cholinergic receptors of autonomic effector cells of the bladder smooth muscle and of the GI tract4. Betanecol increases the tonus of the urinary detrusor muscle and of the vesical trigone , stimulating uretheral movements, relaxing urethral external sphincter and producing a contraction strong enough to trigger micturition and bladder emptying without however changing analgesia levels 3,5.

Betanecol was administered to 26 patients with spinal morphine-induced urinary retention and who did not respond to conventional treatments. Results were satisfactory in 14 patients. The drug was effective only after 25 mg and the best results were obtained with 50 mg and from 6 to 12 hours after surgery. No adverse reactions were observed during this study.

Our results show that betanecol seems to be a good coadjuvant in treating spinal morphine-induced urinary retention.

However, a larger study is needed to evaluate other doses to obtain an effective dose free from side-effects and that would promote the fastest bladder emptying.



01. Manica J - Anestesiologia Princípios e Técnicas. 2ª Ed, São Paulo, Artes Médicas, 1997;288-293.         [ Links ]

02. O’Reilly PH - Postoperative urinary retencion in men, B M J, 1991;302:864.         [ Links ]

03. Goodman e Gilman - As Bases da Farmacologia Terapêutica, 9ª Ed, Rio de Janeiro, Guanabara Koogan, 1995;103-108.         [ Links ]

04. Riella MC - Princípios de Nefrologia e Distúrbios Hidroelétricos, 2ª Ed, Rio de Janeiro, Guanabara Koogan, 1988;438-439.         [ Links ]



Mail to:
Dr. Clóvis José da Silva Borges
Address: Av. Oceano Pacífico, 702/302/B Intermares
ZIP: 58036-310 City: Cabedelo, Brazil

Submitted for publication September 27, 2000
Accepted for publication January 31, 2001



* Received from Hospital Universitário Lauro Wanderley da Universidade Federal da Paraúba UFPB), João Pessoa, PB

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