Factors associated with pain medication selection among patients diagnosed with diabetic peripheral neuropathic pain: a retrospective study

OBJECTIVE

To assess the demographic and clinical characteristics associated with initiation of duloxetine therapy compared with other pharmacologic therapies for treatment of diabetic peripheral neuropathic pain (DPNP).

METHODS

This study used administrative claims databases for commercially-insured individuals aged 18-64 years to examine factors associated with treatment among DPNP patients who initiated duloxetine versus tricyclic antidepressants (TCAs), venlafaxine, gabapentin, pregabalin, or opioids between 7/1/2005 and 12/31/2007. Treatment initiation was defined as no pill coverage of the same medication over the previous 90 days. Multiple logistic regression models were estimated to assess factors associated with initiating duloxetine versus each of the other DPNP therapies.

RESULTS

The study included 11,060 DPNP patients with average age of 55 years old. Cardiovascular disease (63-70%), cerebrovascular/peripheral vascular disease (26-33%), low back pain (24-39%), and osteoarthritis (17-26%) were the most common diabetes- and pain-related comorbidities. Controlling for demographic and clinical characteristics, patients who received duloxetine or pregabalin in the prior 12-month period were more likely to initiate duloxetine. Patients from other DPNP treatment cohorts, except for those in the pregabalin cohort, were more likely to re-initiate the same prior therapy than begin treatment with duloxetine (all p<0.05). A history of anxiety disorder was significantly associated with initiation of all DPNP treatments other than duloxetine (all p<0.05), except for TCAs. Patients with low back pain were more likely to initiate duloxetine than TCAs or venlafaxine, but less likely to initiate duloxetine than pregabalin or opioids. Patients with infections related to diabetes were less likely to initiate duloxetine than venlafaxine, gabapentin, or opioids.

LIMITATIONS

Because a retrospective administrative claims database was used, this study is subject to selection bias due to unobservable confounders, inability to measure prescriber preferences or characteristics or disease severity.

CONCLUSIONS

Among commercially-insured DPNP patients, those with prior use of duloxetine or pregabalin were more likely to initiate duloxetine than other treatments. The presence of select comorbidities was also associated with specific medication initiation.

Opioid use and healthcare costs among patients with DPNP initiating duloxetine versus other treatments

OBJECTIVE

To compare opioid utilization and healthcare costs over a 1-year period following the initiation with duloxetine versus other standard of care (SOC) treatments among patients with diabetic peripheral neuropathic pain (DPNP).

METHODS

This retrospective cohort study assessed commercially-insured DPNP patients between 18 and 64 years old who initiated duloxetine or other SOC treatments (tricyclic antidepressants, venlafaxine, gabapentin, pregabalin) between 3/1/2005 and 12/31/2005. Initiation was defined as a 90-day period without available study medication. The first dispense date of the study medication was denoted as the index date. Selected patients had no opioid pill coverage during the 90 days prior to initiation. Duloxetine and SOC patients were matched via propensity scoring (1:1 ratio), controlling for demographics, comorbidities, prior healthcare utilization and costs, and prior medication history. Opioid utilization and healthcare costs over the 12-month post-index period were compared between study cohorts.

RESULTS

The matched sample included 117 patients in each of the duloxetine and SOC cohorts. Compared with SOC-treated patients, duloxetine-treated patients were less likely to use any opioids (52.1 vs. 84.6%, p < 0.05) over the 12-month post-index period. Duloxetine-treated patients, on average, had two fewer opioid prescriptions dispensed, 27 fewer days on opioids, 121 days greater delay in subsequent opioid use, and 1815 mg lower morphine equivalent dosage than SOC-treated patients (all p < 0.05). Also, duloxetine-treated patients had significantly lower total ($18,623 vs. 30,602, p < 0.05) and outpatient costs ($7371 vs. 15,343, p < 0.05). Due to the use of a retrospective administrative claims database, limitations of this study include the potential for selection bias between study cohorts, and inability to measure unobservable confounding and disease severity and/or duration.

CONCLUSIONS

Among commercially-insured DPNP patients, duloxetine-treated patients had delayed and reduced opioid use and lower healthcare costs than SOC-treated patients.

Changes in opioid use and healthcare costs among U.S. patients with diabetic peripheral neuropathic pain treated with duloxetine compared with other therapies

OBJECTIVE

To examine changes in opioid use and healthcare costs among commercially insured patients with diabetic peripheral neuropathic pain (DPNP) who initiated duloxetine versus other standard of care (SOC) medications (tricyclic antidepressants, venlafaxine, gabapentin, pregabalin).

RESEARCH DESIGN AND METHODS

Using an administrative claims database, patients with DPNP aged 18-64 who initiated duloxetine or SOC between March 1, 2005 and December 31, 2005 were identified. Initiation was defined as a 90-day clean period without the available study medication. Selected patients had 12 months of continuous enrollment before and after the index date, and at least one opioid dispensed in the prior 90 days. Duloxetine and SOC patients were further classified into continuous and non-continuous users based on whether the medication possession ratio was > or =0.8. Total opioid days, number of opioid prescriptions dispensed, and cumulative morphine equivalents were examined over the 12-month pre- and post-index periods. Multivariate regressions were applied to assess the changes (pre-index minus post-index) in opioid use (total, short-acting vs. long-acting) and healthcare costs, controlling for demographic and clinical characteristics.

RESULTS

The study sample included 1281 patients: 98 duloxetine continuous, 243 duloxetine non-continuous, 195 SOC continuous, and 745 SOC non-continuous users. Controlling for demographic and clinical characteristics, duloxetine non-continuous and SOC (continuous and non-continuous) patients had significantly less reduction in total opioid days (-24.4, -23.7, -18.5, respectively, all p < 0.05) from the 12-month pre-index to the post-index period than duloxetine continuous patients. Compared with duloxetine non-continuous, SOC continuous, and SOC non-continuous users, duloxetine continuous users had a greater reduction in short-acting hydrocodone use (difference between the 12 month pre-index and post-index periods) in terms of the total number of prescriptions dispensed (adjusted differences: 1.5, 1.7, 1.7, respectively, all p < 0.05), total supply days (adjusted differences: 28.1, 27.3, 29.7, respectively, all p < 0.05), and morphine equivalent dosage (adjusted differences: 1290 mg, 1132 mg, 1127 mg, respectively, all p < 0.05). Duloxetine non-continuous patients had significantly higher adjusted total ($12,729, p < 0.05) and inpatient costs ($14,993, p < 0.05) than duloxetine continuous patients.

LIMITATIONS

Due to the use of a retrospective administrative claims database, this study is subject to selection bias between study cohorts, misidentification of DPNP and/or other comorbidities, and an inability to confirm adherence to therapy or assess indirect costs and costs of over-the-counter medications.

CONCLUSIONS

Among commercially insured patients with DPNP, continuous treatment with duloxetine was associated with a reduction in opioid use between the 12-month pre- and post-index periods compared with treatment with SOC or non-continuous treatment with duloxetine. Duloxetine continuous patients also incurred lower subsequent healthcare costs than non-continuous duloxetine patients.

Duloxetine compliance and its association with healthcare costs among patients with diabetic peripheral neuropathic pain

OBJECTIVE

Duloxetine is approved to treat diabetic peripheral neuropathic pain (DPNP) in the US. The study objective was to examine the predictors of duloxetine compliance, and its association with healthcare costs among DPNP patients.

METHODS

The study used administrative claims databases to identify non-depressed DPNP patients with a duloxetine prescription dispensed between October 1, 2004 and December 31, 2006. Two cohorts of patients were constructed based on compliance to duloxetine therapy over 1-year follow-up with high compliance defined as a medication possession ratio (MPR) > or =0.80. All-cause, diabetes-, and DPNP-related healthcare costs during 1-year follow-up were estimated. Logistic regressions were performed to examine how average daily dose (ADD) of duloxetine and other factors may influence compliance. Multivariate regressions were estimated to examine the association between compliance and healthcare costs.

RESULTS

The study included 1,380 commercially insured (mean age 55 years) and 974 patients with employer-sponsored Medicare supplemental insurance (mean age 75 years). In both populations, patients with an ADD >30 mg were more likely to be compliant with the therapy compared with those with an ADD of < or =30 mg (odds ratio ranged 1.79-3.38, all p<0.05). Controlling for differences in demographics, clinical and economic characteristics, commercially insured low duloxetine compliance patients had greater all-cause ($5,334, p<0.05) and diabetes-related healthcare costs ($3,414, p<0.05) than high-compliance patients, with the biggest difference from inpatient costs (all-cause: $7,508; diabetes-related: $3,785, all p<0.05). Similar trends were found in the Medicare supplemental insured population; however, differences in all-cause healthcare costs were not significant.

CONCLUSIONS

DPNP patients with a higher ADD of duloxetine over a 1-year follow-up period were more compliant with the therapy. Duloxetine patients with high compliance were also associated with lower healthcare costs. Due to the use of a retrospective cohort design on administrative claims database, limitations of this analysis include a lack of formal diagnostic testing of patients, and inability to infer causality or measure factors such as DPNP severity that are not captured in such database.

Emergent combined intracranial thrombolysis and carotid stenting in the hyperacute management of stroke patients with severe cervical carotid stenosis

BACKGROUND AND PURPOSE

The timely re-establishment of intracranial perfusion, the effective prevention of early recurrent strokes, and the limitation of the incidence of reperfusion injury are the major factors that are key to successful treatment of patients with hyperacute stroke who had severe ipsilateral cervical internal carotid artery (ICA) stenosis. In an effort to reduce both the extent of the ongoing neurologic injury and the risk of early recurrent stroke, we have adopted an aggressive combined endovascular approach of intracranial thrombolysis and cervical carotid stent placement during the hyperacute phase. We report on the results of 5 such consecutive patients who presented to our center from January 2003 through January 2005.

MATERIALS AND METHODS

From January 2003 through January 2005, 5 consecutive patients presented to our center with hyperacute strokes and severe ipsilateral cervical ICA stenosis. All were treated with emergent carotid stent placement and intra-arterial thrombolysis. The medical records were reviewed and summarized.

RESULTS

One patient died. The remaining 4 patients had an average hospital stay of 4 days (range, 3-5 days) and a mean National Institutes of Health Stroke Scale (NIHSS) score of 2 (range, 0-3) at the time of discharge. With a mean clinical follow-up of 11 months (range, 6-24 months), all had excellent functional outcome with a modified Rankin score of 0 or 1.

CONCLUSIONS

Data on emergent carotid stent placement in the hyperacute management of stroke are limited. The summarized experience in these 5 patients demonstrates the feasibility of this aggressive therapeutic strategy that may bring about a good outcome.

The anterior spinal artery origin: a microanatomical study

BACKGROUND

Detailed knowledge of the pattern of origin of the anterior spinal artery is critical as surgical and endovascular procedures involving the area of the ventral medulla and the vertebrobasilar junction are commonplace. We conducted a detailed microanatomical study to elucidate the site and pattern of origin of this critically important artery.

METHOD

Nine adult cadaveric heads (18 sides) were examined after injection of colored silicon. In every specimen, the site of origin of the rami of the anterior spinal artery, their course, branching pattern and anastomoses, external diameters, and the distance from neighbor critical vessels were recorded. The dissections were performed with the aid of both the surgical microscope and a 0 degree endoscope.

FINDINGS

The pattern and site of origin of the anterior spinal artery show great variability. Also the distance of the origin of the two rami (right and left) forming the anterior spinal artery from the vertex of the vertebrobasilar junction and from the origin of the posterior inferior cerebellar artery is highly variable.

CONCLUSIONS

Knowledge of the different pattern of origin and course of the proximal portion of the anterior spinal artery is critically important when planning and executing endovascular and surgical procedures involving the distal vertebral artery, the vertebrobasilar junction and the ventral medulla. On the basis of our and other authors' findings, we propose an overall classification of the pattern of origin and distribution of the proximal anterior spinal artery, which has clinical repercussions.

Isolated unilateral sixth nerve palsy as a presenting symptom of cerebral aneurysms. Report of two cases

We describe two patients with intracranial aneurysms who presented with isolated sixth nerve palsy. A 68-year-old woman with gradual onset of horizontal lateral diplopia was found to have a giant aneurysm at the junction of the petrous and cavernous portion of the internal carotid artery. A 58-year-old man presented with gradual onset of occipital pain followed by a sixth nerve palsy. He was found to have a distal anterior inferior cerebellar artery aneurysm which spontaneously thrombosed on subsequent neuroimaging studies. Although uncommon, isolated sixth nerve palsy can be the only neurological sign of an intracranial aneurysm.

Cerebral vasospasm in patients with unruptured intracranial aneurysms

Intracranial arterial vasospasm is a typical sequela of subarachnoid haemorrhage. The association between symptomatic vasospasm and unruptured aneurysms has been sporadically presented in the literature. The pathogenesis of this unusual entity is unclear. The published cases were collected in this review and analysed with regard to timing, clinical presentation and possible relationship with surgical factors. We also added an illustrative case which was recently observed in our department.

Thrombosed giant intracavernous aneurysm with subsequent spontaneous ipsilateral carotid artery occlusion

We report a case of a 47-year-old man with a giant thrombosed aneurysm of the right cavernous internal carotid artery who initially presented with headache, double vision and trigeminal numbness. He experienced subsequent asymtomatic proximal occlusion of the parent vessel, revealed by follow-up angiography. This case illustrates the possibility that a giant thrombosed aneurysm may exert enough compression upon the parent vessel to induce flow stasis with resultant intraluminal thrombosis progressing to occlude the entire parent artery.

Copasetic analysis: a framework for the blind analysis of microarray imagery

From its conception, bioinformatics has been a multidisciplinary field which blends domain expert knowledge with new and existing processing techniques, all of which are focused on a common goal. Typically, these techniques have focused on the direct analysis of raw microarray image data. Unfortunately, this fails to utilise the image's full potential and in practice, this results in the lab technician having to guide the analysis algorithms. This paper presents a dynamic framework that aims to automate the process of microarray image analysis using a variety of techniques. An overview of the entire framework process is presented, the robustness of which is challenged throughout with a selection of real examples containing varying degrees of noise. The results show the potential of the proposed framework in its ability to determine slide layout accurately and perform analysis without prior structural knowledge. The algorithm achieves approximately, a 1 to 3 dB improved peak signal-to-noise ratio compared to conventional processing techniques like those implemented in GenePix when used by a trained operator. As far as the authors are aware, this is the first time such a comprehensive framework concept has been directly applied to the area of microarray image analysis.

In vitro monitoring of rabbit anterior cruciate ligament damage by acoustic emission

Anterior cruciate ligament (ACL) rupture is a major clinical problem leading to instability and degeneration of the knee joint. The problem is compounded by the limited ability of the ACL to heal when ruptured. The existing knowledge regarding the way the ACL ruptures is limited, and this investigation is an attempt to understand the nature of the ruptures using the rabbit as a model. A total of 16 rabbit tibia-ACL-femur complexes were stretched in tension to complete rupture. Four specimens were stretched to failure at a displacement rate of 0.5 mm/min and 12 specimens at 10 mm/min. Acoustic emission (AE) transducers were placed on both the tibia and the femur, and stress wave signals generated during the tensile test were recorded. Fibre fractures produced the highest amplitude signals with a relatively longer rise time. Other failure modes such as matrix failure and debonding produced lower amplitude signals with shorter rise times. We also noted that few events were recorded during the initial period of tensile loading (the elastic phase). The activity then increased significantly after maximum load was reached. The location information provided by the acoustic emission system was consistent with the final site of rupture. We have shown that AE can be used to characterise ligament damage, with fibre pull-outs and fibre fracture producing the highest signal amplitudes.

Escape behaviour in the stomatopod crustacean Squilla mantis, and the evolution of the caridoid escape reaction

The mantis shrimp Squilla mantis shows a graded series of avoidance/escape responses to visual and mechanical (vibration and touch) rostral stimuli. A low-threshold response is mediated by the simultaneous protraction of the thoracic walking legs and abdominal swimmerets and telson, producing a backwards ‘lurch’ or jump that can displace the animal by up to one-third of its body length, but leaves it facing in the same direction. A stronger response starts with similar limb protraction, but is followed by partial abdominal flexion. The maximal response also consists of limb protraction followed by abdominal flexion, but in this case the abdominal flexion is sufficiently vigorous to pull the animal into a tight vertical loop, which leaves it inverted and facing away from the stimulus. The animal then swims forward (away from the stimulus) and rights itself by executing a half-roll. A bilaterally paired, large-diameter, rapidly conducting axon in the dorsal region of the ventral nerve excites swimmeret protractor motoneurons in several ganglia and is likely to be the driver neuron for the limb-protraction response. The same neuron also excites unidentified abdominal trunk motoneurons, but less reliably. The escape response is a key feature of the malacostracan caridoid facies, and we provide the first detailed description of this response in a group that diverged early in malacostracan evolution. We show that the components of the escape response contrast strongly with those of the full caridoid reaction, and we provide physiological and behavioural evidence for the biological plausibility of a limb-before-tail thesis for the evolution of the escape response.

Stochastic acquisition of Qa1 receptors during the development of fetal NK cells in vitro accounts in part but not in whole for the ability of these cells to distinguish between class I-sufficient and class I-deficient targets

Fetal mouse NK cells are grossly deficient in the expression of Ly49 molecules yet show a limited ability to distinguish between wild-type and MHC class I-deficient target cells. In this paper we report that during their development in vitro from immature thymic progenitors, a proportion of C57BL/6 fetal NK cells acquires receptors for a soluble form of the nonclassical class I molecule Qa1b associated with the Qdm peptide, but not for soluble forms of the classical class I molecules Kb and Db. The acquisition of these Qa1 receptors occurs in a stochastic manner that is strictly controlled by cytokines, and in particular is strongly inhibited by IL-4. All fetal NK clones tested, including those that lack detectable Qa1 receptors, express mRNA for CD94 and for both inhibitory and noninhibitory members of the NKG2 family. Fetal NK cells lacking receptors for Qa1 (and also for classical class I molecules) cannot distinguish between wild-type and class I-deficient blasts but, surprisingly, distinguish efficiently between certain wild-type and class I-deficient tumor cells. A variant line that lacks several members of the NKG2 family kills both types of tumor cell equally well, suggesting the existence of NKG2-containing inhibitory receptors that recognize as yet undefined nonclassical class I molecules of restricted distribution.

Sex differences in patients admitted to a regional secure unit

The case notes of all admissions to a Regional Secure Unit over a 12-year period were examined. A higher proportion of females had a diagnosis of personality disorder. Women were less likely to have a prosecuted offence associated with admission but were more likely to be charged with fire-setting. Patients with personality disorder were more likely to be transferred to special hospitals. Women were nearly three times as likely as men to be transferred to maximum security and this was not accounted for by the excess of females with personality disorder. There was net movement of men out of special hospitals whereas the opposite was true for women. Possible explanations for this are discussed.

Spinal dural arteriovenous fistulas: evaluation with MR angiography

PURPOSE

To show that postgadolinium three-dimensional time-of-flight MR angiography shows abnormal intradural vessels associated with spinal dural arteriovenous fistula better than routine MR imaging and provides screening information useful for subsequent diagnostic conventional angiography and/or posttreatment evaluation.

METHODS

Precontrast and postcontrast MR imaging and MR angiograms, as well as subsequent digital subtraction angiograms, were obtained for eight patients with dural arteriovenous fistulas, diagnosed with digital subtraction angiography and verified with surgery. In four patients, MR studies also were obtained after surgery.

RESULTS

All patients had cord hyperintensity of T2-weighted images and postgadolinium enhancement on T1-weighted images. Five had vessellike signal abnormalities in the subarachnoid space on MR. Abnormal intradural vessels were detected in all eight patients with MR angiography. Comparison with digital subtraction angiography revealed these vessels to be primarily enlarged veins of the coronal venous plexus on the cord surface. In six patients, the medullary vein draining the fistula was demonstrated, indicating the level of the fistula, later identified by digital subtraction angiography. After surgical obliteration of the fistula, the draining medullary vein and most or all of the abnormal coronal veins were no longer demonstrated, with decrease or resolution of cord hyperintensity on T2-weighted images.

CONCLUSION

Postgadolinium, spinal MR angiography in cases of suspected dural arteriovenous fistula provides information about intradural veins that supplements the diagnostic value of the MR imaging results, facilitates the subsequent digital subtraction angiography study, and, in treated cases, reflects the success of surgery and/or embolization.

Pharmacological characterization of multidrug resistant MRP-transfected human tumor cells

We have previously identified and characterized a novel member of the ATP-binding cassette superfamily of transport proteins, multidrug resistance protein (MRP), and subsequently demonstrated that its overexpression is sufficient to confer multidrug resistance on previously sensitive cells (Cole et al., Science (Washington DC), 258: 1650-1654, 1992; Grant et al., Cancer Res. 54: 357-361, 1994). In the present study, we have transfected two different eukaryotic expression vectors containing MRP complementary DNA into HeLa cells to study the pharmacological phenotype produced exclusively by overexpression of human MRP. The drug resistance patterns of the two MRP-transfected cell populations were similar. They were characterized by a moderate (5- to 15-fold) level of resistance to doxorubicin, daunorubicin, epirubicin, vincristine, and etoposide, and a low (< or = 3-fold) level of resistance to taxol, vinblastine, and colchicine. The transfectants were not resistant to 9-alkyl anthracyclines, mitoxantrone, or cisplatin. The MRP-transfected cells were also resistant to some heavy metal anions including arsenite, arsenate, and trivalent and pentavalent antimonials but were not resistant to cadmium chloride. Accumulation of radiolabeled vincristine was reduced by 45% in the MRP-transfected cells and could be restored to the levels found in sensitive cells by depletion of ATP. Rates of vincristine efflux did not differ greatly in the sensitive and resistant cells. The cytotoxic effects of vincristine and doxorubicin could be enhanced in a dose-dependent fashion by coadministration of verapamil. Cyclosporin A also increased vincristine toxicity but had less effect on doxorubicin toxicity. The degree of chemosensitization by verapamil and cyclosporin A was similar in MRP-transfected cells and in cells transfected with the vector alone, suggesting that sensitization involved mechanisms independent of MRP expression. Verapamil and cyclosporin A caused a modest increase in vincristine accumulation in the resistant cells but did not restore levels to those of the sensitive cells. Taken together, these data indicate that drug-resistant cell lines generated by transfection with MRP complementary DNA display some but not all of the characteristics of MRP-overexpressing cell lines produced by drug selection in vitro. They further demonstrate that the multidrug resistance phenotype conferred by MRP is similar but not identical to that conferred by P-glycoprotein and includes resistance to arsenical and antimonial oxyanions.

Acute nurse on rotating split

Linda Nazarko's article, Losing the battle of all NHS mothers (Viewpoint, November 24) stuck a chord with me as it echoed the plights I have experienced.