Abstract
Chronic pain associated with painful diabetic peripheral neuropathy (DPN) can be difficult to manage, with pharmacological treatment not always providing adequate relief, trouble maintaining pain relief, or side effects from the treatments. There are few comparisons of drugs that are either licensed for DPN or recommended in the British national formulary (BNF). In an attempt to gain a clearer picture of the impact of pain associated with painful DPN, this thesis study measured quality of life, cognitive function, and subjective sleep along with the pain reducing effects and effects on cognitive function of pregabalin, duloxetine and amitriptyline. These three drugs are categorised in different classes of drug and have differing mechanisms of action on pain and in the central nervous system. Patients were recruited from two hospitals, with a total of 83 patients randomised. The study was conducted over a period of 36 days including 3 residential visits where cognitive function and other measures were recorded. Baseline measures of pain were associated with reduced quality of life, highlighting the impact of pain on this patient population. Baseline measures of pain also correlated with subjective sleep quality and subjective daytime sleepiness, further highlighting how pain affects these patients. All three treatments reduced pain severity as measured by the Brief Pain Inventory (BPI) from visit 1 (baseline) to visit 2 (low dose) and no treatment appeared to be superior with regards to analgesic efficacy. The effects of each drug on cognitive function were modest and in keeping with their known actions on neurotransmission, although the negative effects of amitriptyline were fewer than anticipated. All three treatments improved measures of subjective sleep and reduced daytime sleepiness. Again, no one treatment was superior. Although the treatments reduced pain and improved sleep there was no evidence of improved quality of life within the duration of the study. This study, a comparison of the three main treatments for painful DPN, has revealed that all three treatments are beneficial, and any impact on cognitive function was modest. Correlations between pain and subjective sleep and quality of life allude to the importance of the effective pain management in this patient population.