Use of gabapentin for attenuation of symptoms following rapid opiate detoxification (ROD)--correlation with neurophysiological parameters--

Rapid opiate detoxification (ROD) is a technique whereby the opiate-dependent patient is withdrawn acutely, under anesthesia, from the opioid. Following detoxification, patients experience severe back pain and restlessness often accompanied by a restless-leg-syndrome. We evaluated gabapentin given immediately following detoxification to attenuate these symptoms. In addition, we evaluated the use of the somatosensory-evoked potential (SEP) as a parameter to quantitate pain responses. Patients (n=21; mean age 32.5 +/- 7 SD; 12 males, 9 females) underwent ROD with naltrexone (2 x 50 mg) during propofol anesthesia and artificial ventilation (IPPV). Sympathetic overshoot was attenuated by clonidine, and increased bowl movement was managed by continuous i.v. somatostatin. Back pain, restlessness, and restless-leg-syndrome were treated with gabapentin (1200 mg) in the ICU. Efficacy was assessed by the patient's subjective ratings of restlessness (0-4). In addition, measurements of amplitude (microV), latency (ms) of late N100-peak of the somatosensory evoked potential (SEP), and tolerance to an increased electrical nociceptive stimulus (mA) to the forearm were performed. Data were compared to pre-treatment control and to the period shortly after detoxification. From a mean of 8.4 +/- 2.5 microV, N100-peak increased to a mean of 12.3 microV +/- 3.3 (p < 0.005) following opioid detoxification. Gabapentin reduced amplitude height to a mean of 3.5 +/- 1.5 microV. Also, tolerance to nociceptive stimulus, which had dropped to 4.4 mA, increased to 12.5 mA (p < 0.01), while intensity for restlessness and thrashing of limbs dropped from 3.2 to 1.2 (p < 0.05). The sudden displacement of the opiate from its receptor site induced by naltrexone, resulted in a post inhibitory SEP overshoot with an increase in nociceptive afferent volleys, and a lowering in pain threshold. This was associated with back pain, limb thrashing and a restless-leg-syndrome, all of which could be attenuated by gabapentin. The amplitude of late N100-peak parameter appears to be a potential candidate to quantify the increase of nociception in such patients.

Gabapentin for Neuropathic Cancer Pain: A Randomized Controlled Trial From the Gabapentin Cancer Pain Study Group

Purpose

To determine the analgesic effect of the addition of gabapentin to opioids in the management of neuropathic cancer pain.

Patients and Methods

One hundred twenty-one consecutive patients with neuropathic pain due to cancer, partially controlled with systemic opioids, participated in a multicenter, randomized, double-blind, placebo-controlled, parallel-design, 10-day trial from August 1999 to May 2002. Gabapentin was titrated from 600 mg/d to 1,800 mg/d in addition to stable opioid dose. Extra opioid doses were available as needed. Zero to 10 numerical scale was used to rate average daily pain. The average pain score over the whole follow-up period was used as main outcome measure. Secondary outcome measures were: intensity of burning pain, shooting/lancinating pain, dysesthesias (also scored on 0 to 10 numerical scale), number of daily episodes of lancinating pain, presence of allodynia, and daily extra doses of opiod analgesics.

Results

Overall, 79 patients received gabapentin and 58 (73%) completed the study; 41 patients received placebo and 31 (76%) completed the study. Analysis of covariance (ANCOVA) on the intent-to-treat population showed a significant difference of average pain intensity between gabapentin (pain score, 4.6) and placebo group (pain score, 5.4; P = .0250). Among secondary outcome measures, dysesthesia score showed a statistically significant difference (P = .0077; ANCOVA on modified intent-to-treat population = 115 patients with at least 3 days of pain assessments). Reasons for withdrawing patients from the trial were adverse events in six patients (7.6%) receiving gabapentin and in three patients receiving placebo (7.3%).

Conclusion

Gabapentin is effective in improving analgesia in patients with neuropathic cancer pain already treated with opioids.

Drug maker to pay $430 million in fines, civil damages

Pharmaceutical manufacturer Warner-Lambert has agreed to plead guilty and pay more then $430 million to resolve criminal charges and civil liabilities in connection with its Parke-Davis division's illegal and fraudulent promotion of unapproved uses for the drug Neurontin (gabapentin). The drug was approved by the Food and Drug Administration in December 1993 solely for use with other drugs to control seizures in people with epilepsy.

Modulation of matrix metalloproteinase production from human lung fibroblasts by type 4 phosphodiesterase inhibitors

Over-expression of matrix metalloproteinases by lung fibroblasts has been blamed for much of the tissue destruction associated with airway inflammation. Because cyclic AMP is known to regulate fibroblast proliferation, as well as cytokine and extracellular matrix protein production, the current study was designed to evaluate the ability of three selective phosphodiesterase (PDE) type 4 inhibitors, rolipram, cilomilast and CI-1044, to inhibit extracellular matrix degradation. Using zymography and ELISA, we found that pro-MMP-2 release was enhanced following 24 h treatment of human lung fibroblast (MRC-5) with TGF-beta1 (10 ng/ml) or TNF-alpha (10 ng/ml), whereas PMA (0.02 microM) had no effect. One hour of pre-incubation with PDE4 inhibitors (10 microM) induced an inhibition of TNF-alpha-stimulated pro-MMP-2 release. Zymography and immunoblotting revealed that fibroblasts cultured with PMA or TNF-alpha released increased amounts of pro-MMP-1, whereas TGF-beta1 had no effect. Incubation with CI-1044 or cilomilast significantly prevented the TNF-alpha increase in pro-MMP-1. These results suggest that PDE4 inhibitors are effective in inhibiting the pro-MMP-2 and pro-MMP-1 secretion induced by TNF-alpha and might underline a potential therapeutic benefit of selective PDE4 inhibitors in lung diseases associated with abnormal tissue remodelling.

Profiles in patient safety: when an error occurs

Medical error is now clearly established as one of the most significant problems facing the American health care system. Anecdotal evidence, studies of human cognition, and analysis of high-reliability organizations all predict that despite excellent training, human error is unavoidable. When an error occurs and is recognized, providers have a duty to disclose the error. Yet disclosure of error to patients, families, and hospital colleagues is a difficult and/or threatening process for most physicians. A more thorough understanding of the ethical and social contract between physicians and their patients as well as the professional milieu surrounding an error may improve the likelihood of its disclosure. Key among these is the identification of institutional factors that support disclosure and recognize error as an unavoidable part of the practice of medicine. Using a case-based format, this article focuses on the communication of error with patients, families, and colleagues and grounds error disclosure in the cultural milieu of medial ethics.

Gabapentin for the prevention of postoperative pain after vaginal hysterectomy

Gabapentin alleviates and/or prevents acute nociceptive and inflammatory pain both in animals and volunteers, especially when given before trauma. Gabapentin might also reduce postoperative pain. To test the hypothesis that gabapentin reduces the postoperative need for additional pain treatment (postoperative opioid sparing effect of gabapentin in humans), we gave 1200 mg of gabapentin or 15 mg of oxazepam (active placebo) 2.5 h prior to induction of anaesthesia to patients undergoing elective vaginal hysterectomy in an active placebo-controlled, double blind, randomised study. Gabapentin reduced the need for additional postoperative pain treatment (PCA boluses of 50 microg of fentanyl) by 40% during the first 20 postoperative hours. During the first 2 postoperative hours pain scores at rest and worst pain score (VAS 0-100 mm) were significantly higher in the active placebo group compared to the gabapentin-treated patients. Additionally, pretreatment with gabapentin reduced the degree of postoperative nausea and incidence of vomiting/retching possibly either due to the diminished need for postoperative pain treatment with opioids or because of an anti-emetic effect of gabapentin itself. No preoperative differences between the two groups were encountered with respect to the side effects of the premedication. However, 15 mg oxazepam was more effective in relieving preoperative anxiety than 1200 mg gabapentin.

Input resistance is voltage dependent due to activation of Ih channels in rat CA1 pyramidal cells

The contribution of the hyperpolarization-activated cation current (I(h)) to input resistance (R(N)) and resting potential (RP) was investigated during whole-cell patch-clamp recordings in CA1 pyramidal cells of rat hippocampal slices. In current-clamp mode, R(N) was determined at different membrane potentials. R(N) decreased with increasing hyperpolarization, from about 260 Momega to 140 Momega at potentials of about -60 mV and -110 mV, respectively. Both the potential of half-maximal reduction of R(N) and the potential of half-maximal I(h) activation (determined in voltage-clamp mode) were approximately -90 mV. The analysis of the voltage sag indicative of I(h) activation revealed a preferential activity of I(h) channels in a voltage range between -70 and -95 mV. ZD7288 (50 microM), a specific I(h) blocker, led to a hyperpolarization by about 4.8 mV, increased R(N) by approximately 45% within a potential range between -65 and -80 mV, and abolished the voltage dependence of R(N). Gabapentin (GBP, 100 microM), an I(h) channel agonist, led to a depolarization by about 2.4 mV and reduced R(N) by about 20% within a potential range between -65 and -80 mV. In conclusion, our data show that R(N) is voltage dependent due to I(h) channel activation and that I(h) channels are preferentially active at voltages between -70 and -95 mV. Furthermore, we demonstrated that R(N) can be modulated by antiepileptic drugs such as GBP, which may partly explain its antiepileptic effect as due to decreasing the sensitivity to excitatory input.

Cytokines modulate cilomilast response in lung fibroblasts

Fibroblasts, as a major source of extracellular interstitial connective tissue matrix, play an important role in wound healing and the development of fibrosis. The phosphodiesterase (PDE) 4 inhibitor cilomilast inhibits fibroblast chemotaxis and fibroblast-mediated gel contraction. Using the Boyden blindwell chamber chemotaxis assay and the type I collagen gel contraction model, this study investigated whether specific cytokines modulate cilomilast's inhibitory effect through regulation of endogenous PGE(2) production. Human recombinant IL-1beta stimulated PGE(2) production and shifted the cilomilast concentration-dependence curve to the left in both assay systems, indicating increased sensitivity to cilomilast. In contrast, human recombinant IL-4 inhibited PGE(2) production and shifted the cilomilast concentration-dependence curve to the right in both systems. In summary, the inhibitory effect of cilomilast on fibroblast migration and collagen gel contraction is modulated by IL-1beta and IL-4 through regulation of PGE(2) production.

PDE4 inhibitors in COPD—a more selective approach to treatment

Chronic obstructive pulmonary disease (COPD) is a serious and mounting global public health problem. Although its pathogenesis is incompletely understood, chronic inflammation plays an important part and so new therapies with a novel anti-inflammatory mechanism of action may be of benefit in the treatment of COPD. Cilomilast and roflumilast are potent and selective phosphodiesterase (PDE)4 inhibitors, with an improved therapeutic index compared with the weak, non-selective PDE inhibitor, theophylline. Unlike theophylline, which is limited by poor efficacy and an unfavourable safety and tolerability profile, the selective PDE4 inhibitors are generally well tolerated, with demonstrated efficacy in improving lung function, decreasing the rate of exacerbations and improving quality of life, with proven anti-inflammatory effects in patients with COPD. Theophylline is a difficult drug to use clinically, requiring careful titration and routine plasma monitoring due to the risk of toxic side effects, such as cardiovascular and central nervous system adverse events, with dose adjustments required in many patients, including smokers, the elderly and some patients on concomitant medications. In contrast, the selective PDE4 inhibitors are convenient medications for both patient and physician alike. Hence these agents represent a therapeutic advance in the treatment of COPD, due to their novel mechanism of action and potent anti-inflammatory effects, coupled with a good safety and tolerability profile.

Effectiveness of Gabapentin for Treatment of Burning Mouth Syndrome

Burning mouth syndrome is a debilitating disorder involving oral pain that may have at least 4 underlying causes. Although several treatments have been proposed, none seems to be universally effective. We report the case of a 67-year-old woman with unremitting oral burning that is increased with the application of anesthetic agents. Initial treatments with nortriptyline hydrochloride and sertraline hydrochloride were contraindicated because of adverse effects, but the administration of gabapentin significantly reduced oral burning. The present case illustrates the effectiveness of gabapentin as a treatment of burning mouth syndrome.

Efficacy and tolerability of the new antiepileptic drugs, II: Treatment of refractory epilepsy: report of the TTA and QSS Subcommittees of the American Academy of Neurology and the American Epilepsy Society

PURPOSE

To assess the evidence demonstrating efficacy, tolerability, and safety of seven new antiepileptic drugs (AEDs) [gabapentin (GBP), lamotrigine (LTG), topiramate (TPM), tiagabine (TGB), oxcarbazepine (OXC), levetiracetam (LEV), and zonisamide (ZNS)] in the treatment of children and adults with refractory partial and generalized epilepsies.

METHODS

A 23-member committee, including general neurologists, pediatric neurologists, epileptologists, and doctors in pharmacy, evaluated the available evidence based on a structured literature review including MEDLINE, Current Contents, and Cochrane Library for relevant articles from 1987 to March 2003.

RESULTS

All of the new AEDs were found to be appropriate for adjunctive treatment of refractory partial seizures in adults. GBP can be effective for the treatment of mixed seizure disorders, and GBP, LTG, OXC, and TPM for the treatment of refractory partial seizures in children. Limited evidence suggests that LTG and TPM also are effective for adjunctive treatment of idiopathic generalized epilepsy in adults and children, as well as treatment of the Lennox-Gastaut syndrome.

CONCLUSIONS

The choice of AED depends on seizure and/or syndrome type, patient age, concomitant medications, and AED tolerability, safety, and efficacy. The results of this evidence-based assessment provide guidelines for the prescription of AEDs for patients with refractory epilepsy and identify those seizure types and syndromes for which more evidence is necessary.

Pilot study using gabapentin for tamoxifen-induced hot flashes in women with breast cancer

In this pilot study, 22 women with breast cancer on tamoxifen therapy with at least two hot flashes a day took oral gabapentin at 300 mg three times a day for 4 weeks. The 16 women who completed the study had a mean decrease in hot flash duration of 73.6% (P = 0.027), frequency of 44.2% (P < 0.001), and severity of 52.6% (P < 0.001), with a complete response in 8/16 women. Side effects reported by four women who did not complete 4 weeks of the study were nausea (1/4), rash (1/4) and excessive sleepiness (3/4). Two additional patients did not provide complete data. Gabapentin is a promising new agent in the treatment of tamoxifen induced hot flashes, and should be studied further.

Amenorrhea in a Patient After Treatment With Gabapentin for Complex Regional Pain Syndrome Type II

A 35-year-old woman suffered a traumatic injury to her right sciatic nerve requiring nerve exploration and external neurolysis. Following the surgery, the patient developed complex regional pain syndrome (CRPS) type II and was treated with gabapentin for pain control. Three months after the initiation of gabapentin therapy (1800 mg/day), the patient reported complete cessation of her menses. Based on hormonal tests, her gynecologist concluded that her amenorrhea was secondary to gabapentin therapy. The patient was weaned off the gabapentin over 6 days with return of her menses 2 weeks later. I conclude that gabapentin has the potential to cause amenorrhea with return of menses occurring after discontinuation of the drug.

The Analgesic Effects of Gabapentin After Total Abdominal Hysterectomy

We investigated, in a randomized, placebo-controlled, double-blind study, the efficacy and safety of gabapentin on pain after abdominal hysterectomy and on tramadol consumption in patients. The 50 patients were randomized to receive either oral placebo or gabapentin 1200 mg 1 h before surgery. Anesthesia was induced with propofol and maintained with sevoflurane in 50% N(2)O/O(2) with a fresh gas flow of 2 L/min (50% N(2)O in O(2)) and fentanyl (2 microg/kg). All patients received patient-controlled analgesia with tramadol with a 50 mg initial loading dose, 20 mg incremental dose, 10-min lockout interval, and 4-h limit of 300 mg. The incremental dose was increased to 30 mg if analgesia was inadequate after 1 h. Patients were studied at 4, 8, 12, 16, 20, and 24 h for visual analog (VAS) pain scores, heart rate, peripheral oxygen saturation, mean arterial blood pressure, respiratory rate, sedation, and tramadol consumption. The VAS scores in the sitting and supine position at 1, 4, 8, 12, 16, and 20 h were significantly lower in the gabapentin group when compared with the placebo group up to 20 h after surgery. The tramadol consumption at 12, 16, 20, and 24 h and total tramadol consumption were significantly less in the gabapentin group when compared with placebo group. Sedation scores were similar at all the measured times. There were no differences between groups in adverse effects. Preoperative oral gabapentin decreased pain scores and postoperative tramadol consumption in patients after abdominal hysterectomy.

IMPLICATIONS

This randomized, controlled trial examined the effects of preoperative oral gabapentin 1200 mg on postoperative pain and tramadol consumptions. We conclude that preoperative oral gabapentin is effective in reducing postoperative pain scores and tramadol consumption in patients after abdominal hysterectomy.

Characteristic of Interactions Between Intrathecal Gabapentin and Either Clonidine or Neostigmine in the Formalin Test

Intrathecal gabapentin is effective for phase 2 of the formalin response but not for acute pain. Unlike gabapentin, intrathecal clonidine and neostigmine attenuate both acute pain and phase 2 of the formalin response. We evaluated gabapentin's interactions with either clonidine or neostigmine in the formalin test. Male Sprague-Dawley rats were used. For the formalin test, 50 microL of 5% formalin solution was injected into the hindpaw. The interaction of drugs was investigated by a fixed-dose analysis or an isobolographic analysis. Intrathecal gabapentin produced a suppression of the phase 2 flinching response, but not the phase 1 response, in the formalin test. Intrathecal clonidine and neostigmine resulted in a reduction of the pain behavior in both phases. A fixed-dose analysis in phase 1 showed that gabapentin potentiated the antinociceptive effect of clonidine and neostigmine. An isobolographic analysis in phase 2 revealed a synergistic interaction after intrathecal administration of gabapentin-clonidine or gabapentin-neostigmine mixture. We conclude that the combination of gabapentin with either clonidine or neostigmine at the level of the spinal cord could play a major role not only in acute pain, but also in phase 2 of the formalin response.

IMPLICATIONS

We determined the pharmacological properties of gabapentin combined with either clonidine or neostigmine in the formalin test. Spinal gabapentin reinforced the effects of clonidine and neostigmine in the formalin test. The hitherto unreported action of gabapentin on acute nociceptive stimulus could be of considerable significance.