Clinical Pharmacology 168.734
In Women undergoing Mastectomy ± Auxiliary Node Dissection / Removal,
how does the
Pre-emptive administration of Gabapentin compared to Venlafaxine affect the incidence of post mastectomy pain syndrome at a 6 month post-surgery review date?
Elective and Acute General and Vascular Surgery (A4)
Hawkes Bay District Health Board
Pain Management Resource Nurse for A4
Goal to become Clinical Nurse Specialist in Pain Management
Post Mastectomy Pain Syndrome (PMPS) affects between 20-60% of women who had a mastectomy [1-14]. “Poorly managed pain can slow recovery, create burdens for patients & their ...view middle of the document...
It has a broad neurotransmitter profile not unlike the tricyclics & has a similar structure to Tramadol, a proven analgesic with opioid agonist & monoaminergic activity [2,54]. It’s first reported use as an analgesic was in 1996 by Songer et al [2,55]. There have been numerous studies that look at pre-emptive / prophylactic analgesia pre-operatively[1,2,14,21,31,32,37,39-42,45-47,50,51]. Amr et al [1,2,47] compare the perioperative use of Venlafaxine or Gabapentin on acute & chronic post mastectomy pain. It studied 150 pts that involved partial or radical mastectomy with auxiliary dissection. Double blinded study with the use of a placebo. It utilised 37.5mg Venlafaxine ER (half the recommended dose ) or 300mg Gabapentin as a single dose (NZF recommends TDS dosing due to half life ) which corresponds with [22,25] - single dosing of 300 or 600mg [22,56-58] gabapentin reaches peak plasma concentration (Cmax) in 2-3 hour & with multiple dosing achieves steady state within 24-48h[22,59]. It is excreted by the kidney, so dose adjustment is needed in poor renal function . All were administered at night starting the day before surgery for a total of 10 days (9 days post-op).
The study found that “Gabapentin reduced visual analogue scores (VAS) after movement by clinically significant amounts from day 2 to day 10 (p=0.0003) Venlafaxine reduced VAS after movement, by clinically significant amounts daily from day 8 to 10 (p=0.002). Analgesic consumption was reduced by clinically & statistically significant amounts for gabapentin vs control every day from day 0-10. At 6 months venlafaxine (but not gabapentin) reduced the incidence of burning pain by clinically & statistically significant amounts (venlafaxine =2%, gabapentin =12%, control=22%; p=0.0018). At 6 months, venlafaxine (but not gabapentin) reduced the incidence of stabbing/pricking pain by clinically & statistically significant amounts (venlafaxine=14%, gabapentin=32%, control=40% p<0.05)”1,2]. It appears from other studies that the 10 day perioperative medicating plan has the best effect (see appendix) in reducing VAS after movement. In one study there was no statistical difference between a single dose of gabapentin vs control at 3 month review (70% gabapentin vs 66% control, p = 0.72) .  Found gabapentin to be effective in prevention of post op nausea & vomiting (PONV) as an incidental finding from other studies RR0.76 (CI 95% 0.58-0.98). In concluding, results from reviewed studies show that pre-emptive use of Venlafaxine significantly reduces the incidence of PMPS at the 6 month review mark, whereas gabapentin is more effective in the post-operative phase (0-10 days). There does not appear to be any studies using both drugs together. This evidence is very thought provoking & already I have had interesting conversations with a Consultant & CNS Breast. The incidence of PMPS in Hawkes Bay is unknown. So before any changes, the...