title: Metamizole versus placebo for panretinal photocoagulation pain control: a prospective double-masked randomized controlled study.
abstract: BACKGROUND
  Diabetic retinopathy is one of most common and threatening ocular diseases. Many of these patients need to be submitted to panretinal photocoagulation (PRP), experiencing a significant level of pain. The purpose of this study is to evaluate the effectiveness of oral metamizole in reducing pain during PRP in patients with proliferative diabetic retinopathy (PDR) and very severe non-proliferative diabetic retinopathy (VSNDR).
  
  
  METHODS
  Patients from a single center with PDR or VSNDR and indication of bilateral PRP were recruited for a double-masked, controlled, prospective study. The treated eyes were randomly assigned in two groups, and each patient had one eye assigned per group. Group A received 1000 mg of metamizole and group B received a placebo pill 40 min before the laser treatment. The groups were switched for the treatment of the fellow eye. Each patient scored the pain sensation immediately after each PRP section using Scott's visual analogue scale (VAS). The paired Student t test was used to measure the significance between the two groups VAS scores, with significance level adopted ofp< 0.05.
  
  
  RESULTS
  Twenty-one patients were recruited. The level of pain was significantly lower when submitted to PRP after oral metamizole treatment compared to placebo (p = 0.002). The mean pain scores for groups A and B were 4.72 ± 1.708 and 5.89 ± 1.967, respectively. The minimum/maximum scores within groups A and B were 1/8 and 1/10, respectively.
  
  
  CONCLUSIONS
  The use of 1000 mg of metamizole 40 min before PRP significantly reduces the pain associated with the procedure in patients with PDR or VSNDR.
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.
authors.forename: Rafael Barbosa
authors.identifier: 0000-0003-4607-1093
authors.initials: RB
authors.lastname: de Araújo
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.|Hospital das Clínicas of University of Sao Paulo Medical School-HCFMUSP, São Paulo, Brazil.
authors.forename: Leandro Cabral
authors.initials: LC
authors.lastname: Zacharias
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.|Hospital das Clínicas of University of Sao Paulo Medical School-HCFMUSP, São Paulo, Brazil.
authors.forename: Breno Marques
authors.initials: BM
authors.lastname: de Azevedo
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.|Hospital das Clínicas of University of Sao Paulo Medical School-HCFMUSP, São Paulo, Brazil.
authors.forename: Beatrice Schmidt
authors.initials: BS
authors.lastname: Giusti
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.|Hospital das Clínicas of University of Sao Paulo Medical School-HCFMUSP, São Paulo, Brazil.
authors.forename: Rony Carlos
authors.initials: RC
authors.lastname: Pretti
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.|Hospital das Clínicas of University of Sao Paulo Medical School-HCFMUSP, São Paulo, Brazil.
authors.forename: Walter Y
authors.initials: WY
authors.lastname: Takahashi
authors.affiliation: Av. Dr. Enéas de Carvalho Aguiar, 255 Cerqueira César, São Paulo, 05403-000 Brazil.|Hospital das Clínicas of University of Sao Paulo Medical School-HCFMUSP, São Paulo, Brazil.
authors.forename: Mário Luiz Ribeiro
authors.initials: MLR
authors.lastname: Monteiro
keywords: Analgesia; Diabetic retinopathy; Metamizole; Pain score; Panretinal photocoagulation