Enhancement of translation by the epsilon element is independent of the sequence of the 460 region of 16S rRNA

The epsilon enhancer element is a pyrimidine-rich sequence that increases expression of T7 gene 10 and a number of Escherichia coli mRNAs during initiation of translation and inhibits expression of the recF mRNA during elongation. Based on its complementarity to the 460 region of 16S rRNA, it has been proposed that epsilon exerts its enhancer activity by base pairing to this complementary rRNA sequence. We have tested this model of enhancer action by constructing mutations in the 460 region of 16S rRNA and examining expression of epsilon-containing CAT reporter genes and recF-lacZ fusions in strains expressing the mutant rRNAs. Replacement of the 460 E.coli stem-loop with that of Salmonella enterica serovar Typhimurium or a stem-loop containing a reversal of all 8 bp in the helical region produced fully functional rRNAs with no apparent effect on cell growth or expression of any epsilon-containing mRNA. Our experiments confirm the reported effects of the epsilon elements on gene expression but show that these effects are independent of the sequence of the 460 region of 16S rRNA, indicating that epsilon-rRNA base pairing does not occur.

A neuropsychological analysis of memory and amnesia

Drawing on neuropsychological studies of amnesic patients, cognitive studies of normal individuals, and functional neuroimaging research, this article reviews recent developments in our understanding of the cognitive and neural bases of various forms of memory. This knowledge provides a foundation for a discussion of the clinical analysis of memory disorders. Different etiologies of selective memory impairment commonly seen in neurological practice are reviewed, followed by an overview of the clinical evaluation of memory disorders. In the evaluation of memory deficits, emphasis is placed on the identification of specific processing deficits that can be linked to underlying neuropathology.

Mutagenesis of the peptidyltransferase center of 23S rRNA: the invariant U2449 is dispensable

U2449 is one of many invariant residues in the central loop of domain V of 23S rRNA, a region that constitutes part of the peptidyltransferase center of the ribosome. In Escherichia coli, this U is post-transcriptionally modified to dihydrouridine (D) and is the only D modification found in E.coli rRNAs. To analyze the role of this base and its modification in ribosomal function, all three base substitutions were constructed on a plasmid copy of the rrnB operon and assayed for their ability to support cell growth in a strain of E.coli lacking chromosomal rrn operons. Both purine substitution mutations were not viable. However, growth and antibiotic sensitivity of cells expressing only the mutant D2449C rRNA was indistinguishable from wild type. We conclude that while a pyrimidine is required at position 2449 for proper ribosomal function, the D modification is dispensable.

Patient-controlled analgesia and intra-operative suggestion

In a double-blind randomised study, we investigated the influence of positive intra-operative suggestions, presented to anaesthetised patients undergoing total abdominal hysterectomy, on postoperative pain, nausea and vomiting. One hundred and forty patients were randomly allocated to listen to one of four tapes containing either white noise or positive suggestions. The positive suggestions related to pain, postoperative nausea and vomiting, or both. We found that the positive intra-operative suggestions had no beneficial effects in reducing postoperative pain or nausea scores, nor was the consumption of morphine or anti-emetics reduced.

Limb sparing surgery for vulvar groin recurrence: a case report and review of the literature

Hemipelvectomy was successfully avoided in a patient with extensive necrotic groin recurrence of vulvar cancer after prior radiation therapy. Tumor-free resection margins were achieved by wide excision of the recurrence including resection of the pubic bone and adjacent muscles. After resection of the femoral artery, blood supply to the leg was restored by an extra-anatomic axillopopliteal bypass. A myocutaneous flap from the contralateral rectus abdominis was used for primary wound closure. Limb salvage was achieved and the patient experienced pain relief, excellent cosmesis, and independent gait. Aspects of treatment options, even though primarily palliative, in groin recurrence of vulvar carcinoma are discussed.

Ipsilateral and contralateral thalamic hypometabolism as a predictor of outcome after temporal lobectomy for seizures

FDG PET is often used to help localize the seizure focus before surgery in patients with medically refractory temporal lobe epilepsy. However, the ability of certain patterns of metabolic landscape to predict postsurgical seizure outcome has not been well characterized. The purpose of this retrospective study was to determine whether FDG PET abnormalities elsewhere in the brain, in combination with those in the temporal lobes, can be used to predict seizure outcome after surgery.

METHODS

Eighty patients with refractory temporal lobe seizures were imaged with PET after intravenous administration of 115 microCi/kg FDG. Images were interpreted without knowledge of clinical information by an experienced reviewer to determine seizure focus and regional metabolic changes in the brain. Metabolic activity scores were assigned for cortical and subcortical structures using the following criteria: 4 = normal activity, 3 = mildly decreased activity, 2 = moderately decreased activity, 1 = severely decreased activity, and 0 = no activity. A laterality index for each region was calculated using the equation 100 x [right - left]/[1/2 x (right + left)]. Seizure focus localization was based on the laterality of temporal lobe metabolic activity and was compared with that determined by scalp and depth electrodes and MRI results. Comparisons were made between asymmetries in metabolic activity in various brain structures and postoperative seizure frequency. Postoperative outcome was determined on the basis of cessation (complete disappearance of seizures) or continuation of seizure activity, regardless of frequency, compared with the preoperative state.

RESULTS

All 64 patients who were free of seizures postoperatively had either no thalamic asymmetry or reduced metabolism on the side from which the temporal lobe was removed. In contrast, 5 of 16 patients (31%) with postoperative seizures of any frequency had hypometabolism in the thalamus contralateral to that of the removed temporal lobe. All 5 patients with reverse thalamic asymmetry had postoperative seizures. Patients with thalamic hypometabolism ipsilateral to the removed temporal lobe also had an increased risk of postoperative seizures, but this risk was not as high as in patients with the contralateral abnormality. In these patients, the temporal lobe (which appeared hypometabolic on PET) was determined to be the site of the seizure on the basis of information besides that provided by PET before surgery.

CONCLUSION

This study indicated that, in patients with temporal lobe epilepsy, thalamic metabolic asymmetry, particularly in the reverse direction to that of the temporal lobe asymmetry, was associated with a poor postsurgical outcome compared with no or matched asymmetry. This determination may be important in evaluating patients for, and selecting optimal candidates for, surgical intervention.

Scanning electron microscopy of sarcophagid (Diptera) larvae recovered from a case of human cutaneous myiasis

Scanning electron microscope observations were made on second instars of unindentified sarcophagid maggots recovered from the foot of a 2-mo-old child. The child had a 3-d history of irritation and swelling of the left foot, and larvae were present in the skin on the plantar surfaces. The lesions were not furuncular, but erythema and a serous exudate were evident and swelling of the infested toes was noted. Larvae were removed manually from the lesions and fixed in formalin. External features, examined by scanning electron microscopy (SEM), were typical for muscomorph larvae and shared features common to other sarcophagids. Details of the cephalic, thoracic, and terminal abdominal sensory structures and variation in the structure of spines from various body regions are described. Comparisons of SEM observations on the cephalic, thoracic, and posterior abdominal regions with other published information did not yield information that allowed the accurate identification of the larvae from this infestation.

A randomized, double-blind trial comparing azithromycin and clarithromycin in the treatment of disseminated Mycobacterium avium infection in patients with human immunodeficiency virus

Two hundred and forty-six patients infected with human immunodeficiency virus (HIV) who also had disseminated Mycobacterium avium complex received either azithromycin 250 mg every day, azithromycin 600 mg every day, or clarithromycin 500 mg twice a day, each combined with ethambutol, for 24 weeks. Samples drawn from patients were cultured and clinically assessed every 3 weeks up to week 12, then monthly thereafter through week 24 of double-blind therapy and every 3 months while on open-label therapy through the conclusion of the trial. The azithromycin 250 mg arm of the study was dropped after an interim analysis showed a lower rate of clearance of bacteremia. At 24 weeks of therapy, the likelihood of patients' developing 2 consecutive negative cultures (46% vs. 56%, P=.24) or 1 negative culture (59% vs. 61%, P=.80) was similar for azithromycin 600 mg (n=68) and clarithromycin (n=57), respectively. The likelihood of relapse was 39% versus 27% (P=.21) on azithromycin compared with clarithromycin, respectively. Of the 6 patients who experienced relapse, none of those randomized to receive azithromycin developed isolates resistant to macrolides, compared with 2 of 3 patients randomized to receive clarithromycin [corrected]. Mortality was similar in patients comprising each arm of the study (69% vs. 63%; hazard, 95.1% confidence interval, 1.1 [0.7, 1.7]). Azithromycin 600 mg, when given in combination with ethambutol, is an effective agent for the treatment of disseminated M. avium disease in patients infected with HIV.

Replaying the game: hypnagogic images in normals and amnesics

Participants playing the computer game Tetris reported intrusive, stereotypical, visual images of the game at sleep onset. Three amnesic patients with extensive bilateral medial temporal lobe damage produced similar hypnagogic reports despite being unable to recall playing the game, suggesting that such imagery may arise without important contribution from the declarative memory system. In addition, control participants reported images from previously played versions of the game, demonstrating that remote memories can influence the images from recent waking experience.

Efavirenz is a potent nonnucleoside reverse transcriptase inhibitor of HIV type 1 replication in microglia in vitro

The objective of this study was to determine whether reverse transcriptase inhibitors (RTIs) could decrease viral replication in microglia. Human microglia obtained from individuals undergoing temporal lobectomy were cultured and infected with HIV-1 isolates from the central nervous system (CNS) as previously described (Strizki JM, et al. J Virol 1996;70:7654-7662). These microglial cultures were treated with one of three nucleoside RTIs (NRTIs) or with efavirenz, a nonnucleoside RTI (NNRTI), at various time points before and during HIV-1 infection. The drug levels sufficient to provide > 90% inhibition of microglial HIV replication (IC90) were determined by comparison of p24(gag) release in the cultures among treated and untreated microglia. Infectious virus released from the infected cultures was also measured with U373-MAGI-CCR5 cells. Efavirenz, an NNRTI, blocked HIV-1(DS-br) infection of microglia with an IC(90) of 0.7-7 nM. This value is similar to the efavirenz IC(90) values for inhibition of laboratory and clinical isolates in lymphocytes, is 2-3 logs lower than the IC90 values of AZT and d4T, and is 1-2 logs lower than that of ddC in microglia. Efavirenz also inhibited infection with other neurotropic isolates, and with viruses isolated from other compartments that also replicated well in microglia. Thus, efavirenz is a potent inhibitor of HIV-1 infection in microglia. Furthermore, efavirenz IC(90) drug levels are present in the cerebrospinal fluid (CSF) of patients taking this once daily NNRTI.

Translation during cold adaptation does not involve mRNA-rRNA base pairing through the downstream box

The downstream box (DB) has been proposed to enhance translation of several mRNAs and to be a key element controlling the expression of cold-shocked mRNAs. However, the proposal that the DB exerts its effects through a base pairing interaction with the complementary anti-downstream box (antiDB) sequence (nt 1469-1483) located in the penultimate stem (helix 44) of 16S rRNA remains controversial. The existence of this interaction during initiation of protein synthesis under cold-shock conditions has been investigated in the present work using an Escherichia coli strain whose ribosomes lack the potential to base pair with mRNA because of a 12 bp inversion of the antiDB sequence in helix 44. Our results show that this strain is capable of cold acclimation, withstands cold shock, and its ribosomes translate mRNAs that contain or lack DB sequences with similar efficiency, comparable to that of the wild type. The structure of helix 44 in 30S ribosomal subunits from cells grown at 37 degrees C and from cells subjected to cold shock was also analyzed by binding a 32P-labeled oligonucleotide complementary to the antiDB region and by chemical probing with DMS and kethoxal. Both approaches clearly indicate that this region is in a double-stranded conformation and therefore not available for base pairing with mRNA.

Biosensor assay of sulfadiazine and sulfamethazine residues in pork

Biosensor-based immunochemical screening assays for the detection of sulfadiazine (SDZ) and sulfamethazine (SMT) in muscle extract from pigs were developed. Samples were extracted with aqueous buffer and then centrifuged. This simple and straightforward preparation allowed up to 40 samples to be processed and analysed in 1 d. The limits of detection for the assays were found to be 5.6 ng g-1 for SDZ and 7.4 ng g-1 for SMT. These figures were well below the European and US legal limits for sulfonamides (100 ng g-1). The precision (RSD) between runs was < 8% and the recovery was between 91 and 98%. The validation proved the assays to be accurate and the analysis of routine field samples showed good correlation with an established TLC screening procedure. No false negative or positive results were obtained with blank and spiked samples. The influence of cross-reacting metabolites on immunoassays was demonstrated by testing incurred tissue samples, collected from sulfonamide treated pigs after only a short withdrawal period. The quantitative results obtained by biosensor analysis were a combination of parent sulfonamide plus N4-acetyl metabolite while the HPLC method used for confirmatory analysis detected only the parent sulfonamide. This gave rise to some false positive results and highlighted the need to use real samples in evaluating any assay thoroughly. False negative results were not obtained.

Mental health in medical students. A case control study using the 60 item General Health Questionnaire

This paper describes a cross-sectional case control study to measure the prevalence of psychological morbidity in first year medical students and compare it to the prevalence in in a randomly selected control group of other first year students at Edinburgh University. The study was conducted anonymously using the 60 item General Health Questionnaire. Participation rates were over 90% in both subjects and controls. A total of 17% of medical students had symptoms of psychological morbidity which may benefit from treatment and a further 29% of medical students had symptoms of psychological distress which would be expected to remit spontaneously. A similar rate was found in the control group of students. This suggests that if medical students or doctors, later in their careers, fare badly in terms of mental health then this may well be related to aspects of their lives and is not an intrinsic characteristic.

Clinical information systems. Do-it-yourself guide

In a 200-bed community hospital, nurse leaders led a team to design, program, and implement a new clinical information system.

The natural course of bulimia nervosa and binge eating disorder in young women

BACKGROUND

Little is known about the relative course and outcome of bulimia nervosa and binge eating disorder.

METHODS

Two community-based cohorts were studied prospectively over a 5-year year period. One comprised 102 participants with bulimia nervosa and the other 48 participants with binge eating disorder (21% [9/42] of whom had comorbid obesity). All participants were female and aged between 16 and 35 years at recruitment. The assessments were at 15-month intervals and addressed eating disorder features, general psychiatric symptoms, and social functioning.

RESULTS

Both cohorts showed marked initial improvement followed by gradual improvement thereafter. Between half and two thirds of the bulimia nervosa cohort had some form of eating disorder of clinical severity at each assessment point, although only a minority continued to meet diagnostic criteria for bulimia nervosa. Each year about a third remitted and a third relapsed. The outcome of the binge eating disorder cohort was better, with the proportion with any form of clinical eating disorder declining to 18% (7 of 40) by the 5-year follow-up. The relapse rate was low among this cohort. There was little movement of participants across the 2 diagnostic categories and few sought treatment. Both groups gained weight, with 39% of the binge eating disorder cohort (14 of 36) meeting criteria for obesity at 5-year follow-up.

CONCLUSIONS

These findings suggest that, among young women in the community, bulimia nervosa and binge eating disorder have a different course and outcome. Whereas the prognosis of those with bulimia nervosa was relatively poor, the great majority of those with binge eating disorder recovered.

Time estimation by patients with frontal lesions and by Korsakoff amnesics

We studied time estimation in patients with frontal damage (F) and alcoholic Korsakoff (K) patients in order to differentiate between the contributions of working memory and episodic memory to temporal cognition. In Experiment 1, F and K patients estimated time intervals between 10 and 120 s less accurately than matched normal and alcoholic control subjects. F patients were less accurate than K patients at short (< 1 min) time intervals whereas K patients increasingly underestimated durations as intervals grew longer. F patients overestimated short intervals in inverse proportion to their performance on the Wisconsin Card Sorting Test. As intervals grew longer, overestimation yielded to underestimation for F patients. Experiment 2 involved time estimation while counting at a subjective 1/s rate. F patients' subjective tempo, though relatively rapid, did not fully explain their overestimation of short intervals. In Experiment 3, participants produced predetermined time intervals by depressing a mouse key. K patients underproduced longer intervals. F patients produced comparably to normal participants, but were extremely variable. Findings suggest that both working memory and episodic memory play an individual role in temporal cognition. Turnover within a short-term working memory buffer provides a metric for temporal decisions. The depleted working memory that typically attends frontal dysfunction may result in quicker turnover, and this may inflate subjective duration. On the other hand, temporal estimation beyond 30 s requires episodic remembering, and this puts K patients at a disadvantage.

Understanding racial variation in the use of coronary revascularization procedures: the role of clinical factors

BACKGROUND

Black patients undergo coronary artery bypass grafting and percutaneous transluminal coronary angioplasty less often than white patients. It is unclear how racial differences in clinical factors contribute to this variation.

METHODS

A retrospective cohort study was performed of 666 male patients (326 blacks and 340 whites), admitted to 1 of 6 Veterans Affairs hospitals from October 1, 1989, to September 30, 1995, with acute myocardial infarction or unstable angina who underwent cardiac catheterization. The primary comparison was whether racial differences in percutaneous transluminal coronary angioplasty and coronary artery bypass grafting rates persisted after stratifying by clinical appropriateness of the procedure, measured by the appropriateness scale developed by the RAND Corporation, Santa Monica, Calif.

RESULTS

Whites more often than blacks underwent a revascularization procedure (47% vs 28%). There was substantial variation in black-white odds ratios within different appropriateness categories. Blacks were significantly less likely to undergo percutaneous transluminal coronary angioplasty (odds ratio, 0.30; 95% confidence interval, 0.14-0.63 [P<.01]) when the indication was rated "equivocal." Similarly, blacks were less likely to undergo coronary artery bypass grafting (odds ratio, 0.44; 95% confidence interval, 0.23-0.86 [P<.01]) when only coronary artery bypass grafting was indicated as "appropriate and necessary." Differences in comorbidity or use of cigarettes or alcohol did not explain these variations. Using administrative data from the Veterans Health Administration, we found no differences in 1-year (5.2% vs 7.4%) and 5-year (23.3% vs 26.2%) mortality for blacks vs whites.

CONCLUSION

Among patients with acute myocardial infarction or unstable angina, variation in clinical factors using RAND appropriateness criteria for procedures explained some, but not all, racial differences in coronary revascularization use.

The incidence and pathogenesis of cardiopulmonary deterioration after abrupt withdrawal of inhaled nitric oxide

We studied the effect of abrupt discontinuation of inhaled nitric oxide (iNO) in patients receiving this drug for treatment of acute hypoxemic respiratory failure (AHRF), in order to determine the need for continued therapy, the incidence and nature of adverse events, and the risk factors predicting these adverse events. Thirty-one patients who showed an initial increase in Pa(O(2)) of > 20 mm Hg in response to iNO underwent a discontinuation trial at 10 to 30 h after beginning iNO. Indwelling arterial and pulmonary artery catheters facilitated monitoring of hemodynamic and gas-exchange parameters. For the group, discontinuation of iNO caused a significant decrease in Pa(O2 ), arterial and mixed venous oxygen saturation, and ratio of Pa(O(2)) to fraction of inspired oxygen (FI(O(2))). Three patterns of response were observed. Eight of 31 (25.8%) patients had minimal changes in oxygenation or hemodynamics, suggesting no need for ongoing therapy. Fifteen of 31 (48%) patients had worsened gas exchange as a predominant response. Eight of 31 patients exhibited hemodynamic collapse, defined as > 20% fall in cardiac output and/or mean arterial blood pressure. In this last subgroup, the pattern of cardiovascular changes suggested that this response arose from an acute increase in right ventricular afterload, and was not a consequence of gas-exchange abnormalities. In all cases, reinstitution of iNO promptly reversed worsened hemodynamics and gas exchange. Independent factors associated with an increased risk of cardiovascular collapse included multisystem organ failure, older age, and initial blood pressure increase in response to iNO; a smaller change in the ratio of Pa(O(2)) to FI(O(2)) with initiation of iNO therapy also tended to correlate with this phenomenon. We conclude that careful and monitored discontinuation of iNO in patients with AHRF will identify substantial fractions of patients who are either receiving no benefit from this therapy or who require iNO to maintain an adequate circulation and are therefore at risk for adverse outcome with transport or inadvertent discontinuation of iNO. Future trials of iNO should recognize this complication of such therapy and include assessments for it.

Three words three shapes: A clinical test of memory

Three Words - Three Shapes was designed as an easy "bedside" test for elderly patients that assesses verbal and nonverbal memory within the same modality. In the present study, it was administered to patients with probable Alzheimer's disease (PRAD), a control group of non-demented older subjects (NC) and a group of patients with Korsakoff's amnesia (KA). Incidental recall and several other measures of learning, retention and recognition differentiated control from PRAD and KA subjects. PRAD and KA subjects' performance was similar, but there were some material-specific interactions. This test is relatively easy and some of the derived measures could prove useful in staging amnesia progression beyond the earliest stages of PRAD when more difficult tests yield floor effects.

Effects of enteric-coated methylnaltrexone in preventing opioid-induced delay in oral-cecal transit time

BACKGROUND

Methylnaltrexone is the first peripheral opioid receptor antagonist. It has the potential to prevent or reverse the peripherally mediated gastrointestinal effects of opioids. In previous human volunteer trials, we demonstrated that oral uncoated methylnaltrexone prevented morphine-induced delay in gastrointestinal transit time.

METHODS

This trial consisted of two studies: a pilot study and a controlled study. The lactulose hydrogen breath test was used to measure the oral-cecal transit time.

RESULTS

In the pilot study with three subjects, an oral dose of 6.4 mg/kg enteric-coated methylnaltrexone effectively reversed the effects of morphine, producing transit times shorter than baseline levels. Subsequently, in the controlled study with another nine subjects, the transit time increased after intravenous morphine administration in all nine subjects, and the lower dose (3.2 mg/kg) of enteric-coated methylnaltrexone completely prevented the morphine-induced change in oral-cecal transit time in all nine subjects. Morphine significantly increased oral-cecal transit time from baseline level of 96.7 +/- 54.1 minutes (mean +/- SD) to 155.0 +/- 53.6 minutes (P = .014). After enteric-coated methylnaltrexone and morphine, the transit time returned to the baseline level (93.3 +/- 56.0 minutes; P = .55 compared with placebo). Plasma concentrations after 6.4 mg/kg and 3.2 mg/kg enteric-coated methylnaltrexone were substantially lower compared with those after 6.4 mg/kg of the uncoated formulation.

CONCLUSION

Our results suggest that there is a prevailing direct and local luminal effect of enteric-coated methylnaltrexone and that the enteric-coated formulation exerts its gut pharmacologic actions more efficiently than the uncoated formulation.

Caldesmon and heat shock protein 20 phosphorylation in nitroglycerin- and magnesium-induced relaxation of swine carotid artery

Nitrovasodilators, high extracellular Mg(2+), and some other relaxing agents can cause smooth muscle relaxation without reductions in myosin regulatory light chain (MRLC) phosphorylation. Relaxations without MRLC dephosphorylation suggest that other regulatory systems, beyond MRLC phosphorylation, are present in smooth muscle. We tested whether changes in caldesmon phosphorylation, heat shock protein 20 (HSP20) phosphorylation, or intracellular pH (pH(i)) could be responsible for relaxation without MRLC dephosphorylation. In unstimulated tissues, caldesmon was phosphorylated 1.02+/-0.10 mol P(i)/mol caldesmon (mean+/-1 S.E.M.), HSP20 was phosphorylated 0.005+/-0.003 mol P(i)/mol HSP20, and estimated pH(i) was 7.21+/-0.07. Histamine stimulation induced a contraction, an intracellular acidosis, but did not significantly change caldesmon or HSP20 phosphorylation. Addition of nitroglycerin induced a relaxation, significantly increased HSP20 phosphorylation to 0.18+/-0.02 mol P(i)/mol HSP20, did not significantly change caldesmon phosphorylation, and pH(i) returned to near unstimulated values. Increase in extracellular Mg(2+) to 10 mM induced a relaxation, but did not significantly change HSP20 or caldesmon phosphorylation. These data suggest that changes in caldesmon phosphorylation, HSP20 phosphorylation, or pH(i) cannot be the sole explanation for relaxation without MRLC dephosphorylation. However, it is possible that HSP20 phosphorylation may be involved in nitroglycerin-induced relaxation without MRLC dephosphorylation.

Methylnaltrexone for reversal of constipation due to chronic methadone use: a randomized controlled trial

CONTEXT

Constipation is the most common chronic adverse effect of opioid pain medications in patients who require long-term opioid administration, such as patients with advanced cancer, but conventional measures for ameliorating constipation often are insufficient.

OBJECTIVE

To evaluate the efficacy of methylnaltrexone, the first peripheral opioid receptor antagonist, in treating chronic methadone-induced constipation.

DESIGN

Double-blind, randomized, placebo-controlled trial conducted between May 1997 and December 1998.

SETTING

Clinical research center of a university hospital.

PARTICIPANTS

Twenty-two subjects (9 men and 13 women; mean [SD] age, 43.2 [5.5] years) enrolled in a methadone maintenance program and having methadone-induced constipation.

MAIN OUTCOME MEASURES

Laxation response, oral-cecal transit time, and central opioid withdrawal symptoms were compared between the 2 groups.

RESULTS

The 11 subjects in the placebo group showed no laxation response, and all 11 subjects in the intervention group had laxation response after intravenous methylnaltrexone administration (P<.001). The oral-cecal transit times at baseline for subjects in the methylnaltrexone and placebo groups averaged 132.3 and 126.8 minutes, respectively. The average (SD) change in the methylnaltrexone-treated group was -77.7 (37.2) minutes, significantly greater than the average change in the placebo group (-1.4 [12.0] minutes; P<.001). No opioid withdrawal was observed in any subject, and no significant adverse effects were reported by the subjects during the study.

CONCLUSIONS

Our data demonstrate that intravenous methylnaltrexone can induce laxation and reverse slowing of oral cecal-transit time in subjects taking high opioid dosages. Low-dosage methylnaltrexone may have clinical utility in managing opioid-induced constipation.