Comparing the pain intensity on a numeric scale (0-10) with intramuscular and subcutaneous injection between a retractable fixed syringe needle and the technique involving needle exchange; Comparing bruise formation following administration of insulin subcutaneous injections between RFS and the conventional technique.

Method Study site A clinical trial was conducted in two medical-surgical units in a hospital in the period from June 15th to November 30th, 2009, after approval by the Ethics and Research Committee.

Intervention In a group of patients the investigators used syringes with retractable fixed needle to administer subcutaneous and intramuscular injections. In the group of control, the investigators used the standard technique to administer medications.

Population of study Patients were sequentially enrolled through a lottery system of exposure using random numbers kept in sealed, opaque envelopes.

Sampling design and sample size Subcutaneous injection The sample size was based on the expected proportion of bruising following the injection. It was expected that 40% of patients would show bruising with the conventional technique and 20% with the technique under study for subcutaneous applications. With an alpha error of 5% (p = 0.05) and power of study of 80% (beta error of 20% or 0.2) 240 patients were included, 120 in each group.

Intramuscular injection The sample size was based on the proportion of patients with moderate to severe pain. It was considered normal the incidence of moderate to severe pain in 30% with a needle exchange, whereas it was considered an increase of up to 40% with the retractable fixed needle. The investigators included 500 patients in each group.

Inclusion Criteria:

• The investigators included all patients over 18 who agreed to participate in the study for subcutaneous and intramuscular injections. The monitoring was done after the reading, comprehension check, and signing of the Term of Free Consent and Clarification.

Exclusion Criteria:

• The investigators excluded patients taking anticoagulants or those who had coagulation disorders, injuries, or skin changes.