Factors influencing time course of pain after depot oil intramuscular injection of testosterone undecanoate

Abstract

Pain following depot intramuscular (IM) injection of oil vehicle-based drugs has been little studied. This study aimed to determine prospectively the prevalence, determinants, severity and functional consequences of pain during the week after IM injection of 1 000 mg testosterone undecanoate (TU) in a 4-mL castor oil vehicle. Androgen-deficient men receiving regular T replacement therapy at an academic andrology clinic were recruited to report pain scores using a coloured visual linear analogue scale at seven times over the first day and daily for a week after a deep IM gluteal injection. The time course and covariables influencing pain scores were analysed by mixed model analysis of variance (ANOVA). Following 168 injections in 125 men, pain was reported by 80% of men, peaking immediately after injection, reaching only moderate severity, lasting 1-2 days and returning to baseline by day 4. The pain required little analgesic use and produced minimal interference in daily activities. The time course of pain scores was reproducible in the 43 men who underwent two consecutive injections. Pain was more severe in men who had an earlier painful injection, but less severe in older and more obese men. There were negligible differences in post-injection pain experience between experienced nurses administering injections. Deep IM gluteal injection of depot TU in 4-mL castor oil is well tolerated and post-injection pain is influenced by earlier painful injection experience, as well as age and obesity.

Figure 1

Any pain (defined as a pain score > 0) before and at various time intervals after 168 intramuscular (IM) injections of 1 000 mg testosterone undecanote (TU) in 4-mL castor oil vehicle into the upper outer quadrant of the buttock region.

Figure 2

Pain scores are plotted as mean and SEM before and at various time intervals after intramuscular (IM) injection of 1 000 mg testosterone undecanote (TU) in 4-mL castor oil vehicle into the upper outer quadrant of the buttock region. The two plots correspond to men with or without a history of pain with earlier TU injections. Dotted line represents overall mean pain score for the whole study.

Figure 3

Pain scores are plotted as mean and SEM before and at various time intervals after intramuscular (IM) injection of 1 000 mg testosterone undecanote (TU) in 4-mL castor oil vehicle into the upper outer quadrant of the buttock region. The three plots correspond to the pain score time course evaluated at three quartiles for age (Q1, 39 years; Q2, 48 years, Q3, 61 years).

Figure 4

Pain scores are plotted as mean and SEM before and at various time intervals after intramuscular (IM) injection of 1 000 mg testosterone undecanote (TU) in 4-mL castor oil vehicle into the upper outer quadrant of the buttock region. The three plots correspond to the pain score time course evaluated at three quartiles for BMI (Q1, 24.6 kg m^{− 2}; Q2, 27.9 kg m^{− 2}; Q3, 31.1 kg m^{− 2}).