Drug consumption and medication
cost analysis after spinal cord
stimulation in chronic pain patients
Moujahed Labidi, MD PGY-II Neurosurgery
Jérome Villeneuve, PhD
Sylvine Cottin, PhD
Sarah-Maude Caron-Cantin
Véronique Briand-Carle
Michel Prud’homme, MD PhD
Léo Cantin, MD FRCSC
Introduction
• Chronic neuropathic pain is a frequent clinical
entity with reported prevalence of 27 % of patients
in pain clinics and up to 8% in the general
population (Torrance et al., 2006). It is a debilitating
and costly disease (Berger et al., 2004)
• In a retrospective review of our cases of spinal cord
stimulation for these patients, we demonstrated
that 40% mean reduction in pain levels, a significant
improvement in quality of life and an 80%
satisfaction rate(unpublished data).
Introduction
• Does SCS reduce medication consumption and
drug cost?
• The cost-effectiveness of the procedure is
established in some indications
o CRPS (Kemler et al., 2002)
o FBSS (Kumar et al., 2002) (North et al., 2007)
• Relatively few data on medication following SCS
implantation
o North et al. 2005
o Kumar et al. 2008
Methods
•
Retrospective observational study of all consecutive patients who
underwent implantation of a SCS between January 1st, 2000 and
June 31st, 2009.
o Consent was obtained from all the participants
•
Baseline characteristics and indication for surgery were obtained
from charts.
•
Medication was assessed with the profiles as effective in the
immediate preoperative period and as of July 2009. They were
obtained from charts and community pharmacies, respectively.
•
Morphine equivalents were calculated according to a published
equianalgesic tables. Total medication cost was calculated on a
price per pill basis, according to our institution’s formulary in July
1st.
Patients
131 SCS implantations
77 Exclusions
-
54 included
patients
23 Data unavailable
20 SCS removed
12 Refusal to participate
8 Invalid data
4 Deceased
3 Non-functioning SCS
2 IT morphine pump
Results
• There was 21 women (39%) and 33 men (61%) and the
mean age at implantation was 50 ± 2 years and 48 ± 2
years for women and men, respectively
• The mean duration since surgery was 33 ± 25 months
• The most frequent indication was FBSS followed by CRPS
Etiology
n
%
FBSS/Chronic radicular pain
30
55.6
CRPS
10
18.5
Multiple sclerosis
2
3.7
Trauma
1
1.9
Peripheral nerve injury
1
1.9
Other neuropathic etiology
8
14.8
N/D
2
3.7
Total
54
100%
Results
Number of patients
Pre SCS Post SCS
Percent
Pre SCS Post SCS
Antiepileptics
26
25
48.15
46.30
Antidepressants
19
21
35.19
38.89
NSAIDs/COX-2 inhibitors/
Salicylate
9
8
16.67
14.81
Benzodiazepines
15
14
27.78
25.93
Hypnotics
1
1
1.85
1.85
Muscles relaxants /
Antispasmodics
1
6
1.85
11.11
Opioids
31
33
57.41
61.11
Other analgesics
6
0
11.11
0.00
Results
• Opiate consumption
*Reduction not associated
with preop level of opiates
or duration since surgery
o Preop : 87 ± 118 mg/d
o Postop : 99 ± 172 mg/d
• P = 0.29
Difference in opiate consumption following SCS
20
33%
18
16
Increase (33%)
Decrease (34%)
14
12
Number of
patients
19%
17%
10
8
11%
6
4
6%
7%
7%
101 to 200
>200
2
0
<-200
-200 to -101
-100 to -1
0
Opiate difference
1 to 100
Results
Opiate consumption and gender
500
Opiate consumption (mg/d)
*
400
300
200
100
0
M
F
Pre SCS
Post SCS
Results
• Total drug costs
o Preop : 181 ± 25 CAD$/m
o Postop : 217 ± 25 CAD$/m
• P = 0.23
*Reduction associated with lower
preop total drug costs (p < 0.05)
Difference in drug cost according to gender
160
140
120
100
Drug cost
difference
(CAD$)
80
*
60
40
20
0
-20
M
F
Results
Correlation between drug cost difference and age
among male patients
Drug cost
difference
(CAD$)
Age
Discussion
• No statistically significant reduction in opiate intake
or drug consumption habits following SCS
implantation
• No statistically significant reduction in total drug
cost either
• However, 67% of patients achieved stabilisation or
even reduction of their opiate intake while noting
improvement in their pain levels and quality of life
Discussion
• There may be a different response and evolution
between genders
o Different threshold and reaction to pain
o Higher prevalence of chronic pain among females
o Different expectations from surgery
• Medication reduction may be harder among patients
taking more medication initially
• Limitations of the study
o
o
o
o
Retrospective design
Significant number of exclusion (59%)
Important variation in duration since implantation of SCS
No standardization of confounding parameters and medical
management
Conclusion
• Opiate consumption reduction is hard to achieve
following SCS
• This may be especially true for female patients
• Actively reducing the medication may be possible
without increasing pain levels; this should be studied
in a prospective fashion in a pain clinic context