Effect of Methylprednisolone Injection Speed on the Perception of Intramuscular Injection Pain

Administration of IM Injection 

For IM injection, five sites can be used, including deltoid, dorsogluteal, rectus femoralis, vastus lateralis, and ventrogluteal sites. Nurses should choose an injection site based on patient age, characteristics of the medication (such as oily or irritating solutions), the volume of medication, and conditions related to the patient (Rodger and King, 2000, Wynaden et al., 2006). To administer the medication properly, nurses should know the bony landmarks and the potential harmful consequences inherent at each site. According to the literature, nurses typically prefer to inject at the dorsogluteal site because its landmarks are easy to locate (Wynaden et al., 2006). Furthermore, large-volume IM injections (3-5 mL) can be administered to the dorsogluteal site of adults and children >3 years old (Carter-Templeton & McCoy, 2008).

Despite the high prevalence of treatments that use IM injection, this route of administration is associated with complications which can be iatrogenic or can emerge from improperly administered injections. Particularly in developing countries, even in health care settings, injections present a risk of blood-borne transmission of hepatitis B and C and human immunodeficiency virus (Nicoll & Hesby, 2002). Even when all aseptic safety precautions are taken, inappropriate performance of IM injection can result in serious complications, including skeletal muscle fibrosis, contracture, pain, nerve injury, bleeding, sterile abscesses, and accidental intravenous administration (Hunter, 2008). When using the dorsogluteal site, nurses should keep in mind that sciatic nerve injuries are primarily associated with the use of this site for injection (Small, 2004).

Evidence for Decreasing the Pain of IM Injection 

Although IM injection is not a benign intervention, and the delivery of medication is fundamental to patient care, it is often seen as a ritualistic practice shared between nurses and not based on research evidence (Carter-Templeton and McCoy, 2008, Floyd and Meyer, 2007, Nicoll and Hesby, 2002). Altıok and Gökçe (2007) reported that nurses' techniques in giving IM injections were traditional rather than evidence based. When nurses recognized the need for information in their practice, their most frequently used source of education was a peer or textbook. Nurses believe that textbooks contain up-to-date research and describe current evidence-based practices regarding techniques and interventions used in the clinical setting (Carter-Templeton & McCoy, 2008). However, in a study comparing five fundamental nursing textbooks, Carter-Templeton and McCoy (2008) found discrepancies among the books pertaining to IM techniques. Due to this tradition-based practice of IM injection, many nurses did not use correct procedures for IM injections to reduce pain and tissue trauma. Furthermore, there is wide variation in the techniques used by nurses to prepare and administer medications (Engstrom et al., 2000, Nicoll and Hesby, 2002).

To minimize complications and pain associated with IM injection, nurses should be familiar with recent literature and develop their skills accordingly (Hunter, 2008, Nicoll and Hesby, 2002). To prevent postinjection pain, nurses need to be knowledgeable of the assessment of pain, psychosocial and cultural factors affecting pain expression, genetic and ethnic determinants of pain threshold and pain tolerance, and, most importantly, current evidence-based practices regarding pain (Miller and Newton, 2006, Monsivais and McNeill, 2007). However, although it is a common nursing practice, there is a paucity of research on IM injection (Cocoman & Murray, 2008).

A limited amount of experimental study has examined the effect of different interventions, such as cold, manual pressure, needle temperature, and injection speed, on injection-site pain for certain medications (Bartell et al., 2008, Chan, 2001, Chung et al., 2002, Jaafari et al., 2004, Kuzu and Ucar, 2001, Zaybak and Khorshid, 2007). Those studies found that the application of ice and manual pressure reduced patient perception of pain at the IM injection site (Chung et al., 2002, Kuzu and Ucar, 2001). However, Bartell et al. (2008) found that needle temperature did not influence pain following IM injection. Regarding the effect of injection speed on postinjection pain, there is sufficient research regarding pain and bruising resulting from SC heparin injections. These studies indicated that pain intensity and pain duration were significantly lower for 30- and 20-second SC heparin injections compared with more rapid injections (Chan, 2001, Jaafari et al., 2004, Zaybak and Khorshid, 2007). However, regarding pain arising from IM injection, one study reported that injection durations of 10 and 30 seconds were not effective at reducing the perception of pain from IM hepatitis B vaccination (Mitchell & Whitney, 2001). There are no further studies concerning pain due to IM injection in the literature.

Because pain is unpleasant for all patients, it should be managed regardless of whether the pain is acute or chronic. Pain originating from IM injection should not be underestimated, because a painful injection might cause the patient to develop a severe fear of injection, known as needle anxiety. Needle anxiety not only affects patient quality of life but also can delay future medical care requests (Cox & Fallowfield, 2007). Therefore, the aim of the present study was to examine the effect of two different IM injection speeds on pain intensity and pain duration to minimize the pain associated with methylprednisolone injection. An additional purpose of the study was to identify the impact of methylprednisolone dose and patient characteristics on pain intensity for two injections speeds.

Method 

Results 

Study Population 

Of the 25 patients, 15 (60%) were men and 10 (40%) were women, with a mean age of 42.7 (range 18-80) years. Patients >40 years old and with normal or low weight (BMI ≤24.9 kg/m2) constituted 60% of the patients. Sixteen patients (64%) were high school and university graduates. Fourteen patients (56%) were not employed, and 11 (44%) were laborers or government employees (Table 1). Although not shown in Table 1, the mean BMI of the patients was 25.9 (range 18-48) kg/m2. Fourteen patients received a dosage of ≥50 mg (range 20-65 mg) of methylprednisolone.

Table 1. Patients' Descriptive Characteristics (n = 25)

		n	%
	Age, yrs
	18-39	10	40
	≥40	15	60
	Gender
	Female	10	40
	Male	15	60
	Body mass index, kg/m2
	≤24.9	15	60
	>25	10	40
	Education level
	≤Elementary	9	36
	≥High school	16	64
	Working state
	Working	11	44
	Not working	14	56
	Profession
	Laborers/government employees	11	44
	Retired	6	24
	Housewife	6	24
	Unemployed	2	8
	Diagnosis
	Urticaria	5	20
	Behcet Disease	4	16
	Dermatitis	4	16
	Psoriasis	3	12
	Pemphigus vulgaris	3	12
	Epidermolysis bullosa	1	4
	Vasculitis	1	4
	Actinic reticuloid	1	4
	Purpura	1	4
	Steven Johnson disease	1	4
	Polyarteritis nodosa	1	4

Impact of Methylprednisolone Administration Speed on Pain 

Mean pain levels, as measured by the VAS, in the postinjection period were significantly greater with administration of IM methylprednisolone in 10 seconds compared with 30 seconds. (t = 3.195; p = .004). Mean pain levels after 10- and 30-second injections were 1.9 and 1.3, respectively. There was no statistically significant difference in mean pain intensity with different methylprednisolone doses (≤45 mg or ≥50 mg) after injection at either speed (10-second injections: F = 0.428; p = .510; 30-second injections: F = 0.645; p = .430).

The severity of pain peaked at 0 minutes (immediately after the injection) for both injection speeds, as summarized in Table 2. However, the duration of pain was longer after a 10-second injection than after a 30-second injection. Although pain typically persisted at the 35-minute time point after a 10-second injection, the pain after a 30-second injection had typically subsided by this point (Table 2). Changes in pain severity in the postinjection period (0, 5, 10, 15, 20, 25, 30, and 35 minutes) were analyzed with respect to the two different administration durations (10 vs. 30 seconds), as summarized in Table 2. At five time points during the postinjection period (0, 10, 15, 20, and 25 minutes), pain was significantly greater after 10-second injections than after 30-second injections (p = .016; p = .036; p = .004; p = .008; and p = 0.013; respectively). However, there were not statistically significant differences in pain severity at 5, 30, and 35 minutes in the same analysis (p = .136; p = .265; and p = .327; respectively; Table 2).

Table 2. Differences between Postinjection Pain (Mean ± SD) by Two Different Speeds (10 vs. 30 s; n = 25)

	Time of Pain Measurement (min after injection)	10 s Injection	30 s Injection	t	p Value
	0	4.1 ± 2.1	3.4 ± 1.6	2.587	.016
	5	3.6 ± 1.9	3.1 ± 1.5	1.542	.136
	10	3.0 ± 1.7	2.2 ± 1.4	2.221	.036
	15	2.2 ± 1.6	1.2 ± 1.2	3.216	.004
	20	1.5 ± 1.5	0.5 ± 0.8	2.918	.008
	25	0.7 ± 1.1	0.1 ± 0.4	2.682	.013
	30	0.2 ± 0.5	0.1 ± 0.4	1.141	0.265
	35	0.1 ± 0.2	0.0 ± 0.0	1.000	0.327

Evaluation of Pain after Two Injection Durations with Respect to Demographic Data 

The severity of pain with respect to age, gender, BMI, and education level after 10- and 30-second injections was evaluated statistically. Pain severity in the two injection groups was not significantly different at 0, 5, 10, 30, and 35 minutes regarding patient demographic characteristics (p > .05). However, male patients showed statistically significant differences in pain at 15 minutes following 10-second injection (p=.056) (Table 3). Although not reached a statistical significance (p=0.099), patients older than 40 years of age experienced greater pain at 15 minutes following 10-second injection (Table 3).

Table 3. Differences between Postinjection Pain (Mean ± SD) by Patient Characteristics (n: 25)

	Time of Pain Measurement (min after injection)	Characteristic	Injection Speed		F/p
			10 s	30 s	10 s	30 s
	15	Age, yrs
		18-39	1.6 ± 1.2	1.1 ± 1.0	2.957	1.294
		≥40	2.5 ± 1.8	1.2 ± 1.2	0.099	0.267
		Gender
		Female	1.7 ± 1.2	0.8 ± 1.3	4.056	0.252
		Male	2.5 ± 1.8	1.4 ± 1.0	0.056	0.620
		BMI, kg/m2
		≤24.9	2.1 ± 1.7	1.2 ± 1.2	0.036	0.003
		≥25	2.3 ± 1.6	1.1 ± 1.2	0.852	0.960
		Education
		≤Elementary	2.1 ± 1.6	0.9 ± 1.2	0.068	0.141
		≥High school	2.1 ± 1.7	1.3 ± 1.1	0.769	0.711
	20	Age, yrs
		18-39	0.8 ± 0.9	0.5 ± 0.7	5.430	0.337
		≥40	1.9 ± 1.7	0.5 ± 0.9	0.029	0.567
		Gender
		Female	1.0 ± 1.2	0.4 x 0.9	2.768	0.000
		Male	1.8 x 1.6	0.6 x 0.7	0.110	10…
		BMI, kg/m2
		≤24.9	1.3 ± 1.4	0.7 ± 1.0	1.825	4.897
		≥25	1.7 ± 1.8	0.3 ± 0.5	0.190	0.037
		Education
		≤Elementary	1.3 ± 1.6	0.2 ± 0.4	0.134	5.577
		≥High school	1.6 ± 1.5	0.7 ± 0.9	0.718	0.027
	25	Age, yrs
		18-39	0.6 ± 0.9	0.2 ± 0.6	0.935	0.344
		≥40	0.7 ± 1.2	0.1 ± 0.2	2.548	0.124
		Gender
		Female	0.2 ± 0.4	0.0 ± 0.0	10.245	6.385
		Male	1.0 ± 1.3	0.2 ± 0.6	0.004	0.019
		BMI, kg/m2
		≤24.9	0.7 ± 1.0	0.2 ± 0.6	0.437	6.385
		≥25	0.7 ± 1.2	0.0 ± 0.0	0.515	0.019
		Education
		≤Elementary	0.3 ± 1.0	0.0 ± 0.0	0.856	0.364
		≥High school	0.9 ± 1.2	0.2 ± 0.5	5.254	0.031

Pain severity 20 minutes after 10-second injection for patients >40 years old and after 30-second injection for patients with normal or low weight (BMI ≤24.9 kg/m2) and a high education level (high school and university graduates) were significantly greater (p = .029; p = .037; p = .027; respectively; Table 3). Although pain severity was not statistically different between the sexes, for both injection durations, pain severity was greater with men than with women (10-second administration: men 1.8, women 1.0; 30-second administration: men 0.6, women 0.4; p > .05; Table 3).

Pain severity 25 minutes after 10- and 30-second injections was statistically higher for men (p = .004; p = .019; respectively). Also at this time point, the pain severity after 30-second injections was statistically greater for patients with normal or low weight (BMI ≤24.9 kg/m2) and high education level (high school and university graduates) (p = .019; p = .031; respectively; Table 3).

Discussion 

This study proved that the severity of pain after injections is altered by the speed of the administration of methylprednisolone. When comparing faster injection (10 seconds) with slower injection (30 seconds), the faster injection produced more pain (10 seconds: 1.9; 30 seconds: 1.3; p < .05). In the literature, there have been ample studies regarding the pain associated with subcutaneous injection of heparin as it relates to the duration of injection (Chan, 2001, Jaafari et al., 2004, Zaybak and Khorshid, 2007). Similarly to the present study, the literature regarding heparin injection suggests that severity of pain increases with the speed of administration (Chan, 2001, Jaafari et al., 2004, Zaybak and Khorshid, 2007). However, in a study evaluating the pain related to IM hepatitis B vaccination, the speed of injection did not affect the pain severity. This finding was explained by the chemical structure of the vaccine and the absorption properties (Mitchell & Whitney, 2001).

In addition, studies in the literature state that the severity of pain peaks shortly after injection. In addition, an inverse correlation between injection speed and pain duration has been observed (Chan, 2001, Jaafari et al., 2004, Zaybak and Khorshid, 2007), which supports the results of the present study. However, changes in pain at different time points in the postinjection period were not evaluated in these studies. In the present study, no difference in pain severity was observed between the administration durations at 5, 30, and 35 minutes following injection. These data suggest that absorption peaked at 5 minutes and was substantially completed after 30 minutes (Uhl et al., 2002).

None of the studies evaluating pain with injection speed investigated changes in pain severity related to drug dosage (Chan, 2001, Jaafari et al., 2004, Mitchell and Whitney, 2001, Zaybak and Khorshid, 2007). In the present study, drug dosage did not affect the severity of pain after two different administration durations. This finding may be explained by the chemical structure of methylprednisolone. Even at high doses, methylprednisolone is absorbed in a short time and eliminated from the body in a few hours (Uhl et al., 2002).

We found statistically significant correlations between demographic parameters (such as age, gender, BMI, and education level of the patients) and the severity of pain. Although, in the literature, pain perception does not change significantly with age, the pressure pain threshold decreases with increasing age (Komiyama et al., 2007, Lautenbacher et al., 2005). In the present study, higher pain severity was associated with age >40 years, which is concordant with the literature, because IM injections lead to pressure source pain (Guyton and Hall, 2000, Komiyama et al., 2007, Lautenbacher et al., 2005). In addition, when considering the pain perception alterations with respect to sociocultural properties and social value judgments, it has been suggested that young individuals, affected by societal expectations of strength, express less of their pain than older patient groups (Edwards, Fillingim, & Keefe, 2001a).

In the literature, a considerable number of studies have investigated pain threshold and pain tolerance with respect to gender and ethnic origin (Dawson and List, 2009, Edwards et al., 2001b, Keogh et al., 2000, Robinson et al., 2003). In all of the studies, men demonstrated significantly higher pain thresholds and pain tolerance than women (Dawson and List, 2009, Keogh et al., 2000, Robinson et al., 2003). However, in the present study, after 10- and 30-second administrations, perception of pain severity for men was statistically higher than for females. This finding demonstrated the importance of sociocultural and ethnic factors in pain perception. (Edwards et al., 2001a, Njobvu et al., 1999). Dawson and List (2009) compared the pain tolerance of Swedish and Middle-Eastern people and found that tolerance of pressure and pain was lower in Middle-Eastern men and women than in Swedish. Similarly, Njobvu et al. (1999) suggested that pain tolerance and pain threshold were lower in Asian than European men and women. There have been no studies evaluating pain tolerance and pain threshold with respect to gender and ethnic origin in the Turkish population.

Furthermore, pain perception can vary among people with different educational backgrounds. In a study by Soares, Sundin, and Jablonska (2004) investigating pain in the context of education level, Swedish patients who were less educated demonstrated lower pain perception. Therefore, pain perception should be viewed as multifactorial and affected by ethnic and socio-cultural factors, such as education (Dawson and List, 2009, Edwards et al., 2001a, Njobvu et al., 1999). In the present study, perception of pain was higher for more educated patients 20 and 25 minutes after a 30-second injection. This finding implies that high school and university graduates may be more aware of their health and bodies. In addition, more educated patients are more conscious of the side effects of medical procedures and can express themselves better than patients with poorer educational backgrounds (Rudd et al., 2009).

In the present study, patients with normal and/or low weight (BMI ≤24.9 kg/m2) demonstrated increased pain severity compared with obese patients at 20 and 25 minutes after a 30-second injection; this difference was statistically significant. An earlier study proposed that obese individuals have lower pain response thresholds and pain tolerance owing to a disturbance in endogenous morphine production (Keller, 2006, Pradalier et al., 1981). Although the pain thresholds and pain tolerance of obese patients are low, because lipid-soluble glucocorticoids distribute in adipose tissue methylprednisolone injection elicits less pain in obese patients (Uhl et al., 2002).

Conclusion 

For all measurements taken 35 minutes after injection, slow IM administration (30 seconds) of methylprednisolone caused less pain than more rapid (10 seconds) administration. Furthermore, pain subsided earlier after slow administration compared with rapid injection. The severity of pain reached its peak level immediately following methylprednisolone injection. The results showed that the pain resulting from methylprednisolone injection did not significantly change with the administered dose of the drug. The main implication for clinical practice is that high-speed IM injection of methylprednisolone should be avoided, regardless of dosage. Certain patient characteristics, such as age, gender, BMI, and education level, should be taken into consideration when administering IM methylprednisolone. In particular, male patients >40 years of age with low body mass and strong educational backgrounds should be considered to be at high risk for experiencing pain after IM methylprednisolone injection.

Although this study was prospective and randomized, it still has limitations. This study was conducted at a single center with a relatively low number of patients. More multicentered studies with increased numbers of patients will provide more definite results.