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Biomedical subjects

L G Allan

Publications and source records attributed to L G Allan.

At least 19 recordsLinked to original sources
PubMed2004

Efficacy and safety of transdermal fentanyl and sustained-release oral morphine in patients with cancer and chronic non-cancer pain.

PURPOSE: To evaluate effectiveness and safety information of transdermal fentanyl (TDF) (Duragesic/Durogesic) and sustained-release oral morphine (SRM) in cancer pain (CP) and chronic non-cancer pain (NCP), a pooled analysis was conducted on datasets of published, open label, uncontrolled (no comparator group) and randomised controlled (with SRM as comparator) studies of TDF. PATIENTS AND METHODS: Eight trials with treatment durations of at least 28 days met the inclusion criteria. The effectiveness analysis assessed changes in average pain and pain 'right now' scores between baseline and Day 28. The safety analysis evaluated the incidence of adverse events (AEs) reported within the first 28 days of treatment with TDF or SRM. Subgroup analyses included pain type, gender, age, weight, and body mass index. RESULTS: Pooled efficacy data were available from 1220 patients; these showed that both TDF and SRM were effective in improving pain 'right now' scores (0-100 scale) from baseline to Day 28. The improvement was significantly more pronounced in the TDF treatment group (-26.7 +/- 31.3 for TDF, -18.7 +/- 30.9 for SRM, p = 0.002). This favourable effect of TDF was most apparent amongst patients with NCP. Data concerning AEs were available from over 2500 patients with CP (3 out of 10 patients) or chronic NCP (7 out of 10 patients). Significantly fewer patients in the TDF than in the SRM group reported any AE (72% vs. 87% respectively; p < 0.001), or an AE leading to the study drug being permanently discontinued (16% vs. 23% respectively; p < 0.001). Constipation and somnolence occurred considerably less frequently in the TDF than in the SRM treatment group. This difference was statistically significant in both the CP and NCP subgroups. CONCLUSION: This pooled data analysis provides expanded insight into the safety and effectiveness profile of transdermal fentanyl in patients with chronic pain. It shows significantly improved pain relief with transdermal fentanyl compared with sustained-release oral morphine, and supports current evidence of favourable tolerability of transdermal fentanyl, particularly with regard to reduced constipation and somnolence.

Administration, Cutaneous↗
PubMed2001

Opioid drugs: a comparative survey of therapeutic and "street" use.

OBJECTIVES: The prescription of strong opioid analgesics for chronic non-cancer pain (CNCP) is described as controversial and can result in misidentification of patients as drug abusers or individuals with an addiction. This study compared the effects of opioid drugs on CNCP patients and "street" users. SUBJECTS/SETTING: The groups comprised 36 CNCP patients attending a pain clinic and 39 street users, recruited on London streets. DESIGN: CNCP patients were interviewed in a pain clinic and street users in a street setting. A questionnaire was used to assess drug craving, dose escalation, cessation of use, compulsion to use, effects on career, relationships and activities, experience of "highs," and problems due to intoxication. To assess physiological dependence, subjects answered questions on specific effects e.g. stomach pains, nausea/vomiting, cramps/aches, etc.). Efficacy was assessed in CNCP patients by determining analgesia and physical function. RESULTS: CNCP patients started therapy in the low dose range for oral morphine (</=60 mg/day) and most (83%) did not move into a higher dose range once adequate levels of analgesia were attained. Street users started smoking heroin intermittently, before daily use. Most escalated their dose by increasing the amount used and by switching from smoking to injecting. Unlike CNCP patients, street users demonstrated patterns of compulsive drug use, social problems and intoxication. Only 3 / 31 (9.5%) pain patients that discontinued opioid therapy reported withdrawal symptoms on abstaining from the drug compared to 35 (89.5%) of street users. CONCLUSION: Findings suggest that CNCP patients prescribed strong opioid analgesics derive more benefit than harm.

Journal Article↗
PubMed2001

Temporal bisection with trial referents.

In temporal bisection, the subject is required to compare the similarity of a probe duration with two referent durations. Two bisection experiments with human subjects are reported in which performance under three referent conditions was compared. In two of the conditions, no-referent and fixed-referent, the referent pair was constant throughout the session and was varied between sessions. In the no-referent condition, samples of the referents were presented at the beginning of a block of trials, but not on the probe trials. In contrast, in the fixed-referent condition, the referent pair was presented on each probe trial. In the third referent condition, roving-referent, the referent pair was also presented on each probe trial, but the values of the pair varied during a session rather than between sessions. The pseudologistic Model (PLM; Killeen, Fetterman, & Bizo, 1997) provided an excellent account of the data from all referent conditions and indicated that (1) the scalar variability was located in the perception of the probe and was independent of the structure of the bisection task, (2) the role of the referents was to set the criterion, (3) the probe was compared with the criterion rather than with the referents, and (4) the comparison of the probe with the criterion occurred even when trial referents were available.

Adult↗
PubMed1998

Learning and homeostasis: drug addiction and the McCollough effect.

The contribution of conditioned responses (CRs) to homeostasis may be seen by examining seemingly disparate phenomena of color vision (aftereffects and chromatic adaptation) and drug addiction (withdrawal symptoms and tolerance). Color aftereffects may be elicited by nonchromatic stimuli previously paired with color (the McCollough effect, [ME]). Similarly, pharmacological aftereffects may be elicited by nonpharmacological stimuli previously paired with a drug (withdrawal symptoms). The authors summarize evidence indicating that both the ME and withdrawal symptoms are CRs. The chromatic CR is expressed as chromatic adaptation in the presence of color, and the ME in the absence of color. The pharmacological CR is expressed as pharmacological adaptation (tolerance) in the presence of the drug, and withdrawal symptoms in the absence of the drug. Both drug withdrawal symptoms and the ME are manifestations of the contribution of conditioning to normal homeostatic regulation. The authors discuss the implications of this conclusion for understanding regulatory processes and the evolution of behavioral mechanisms.

Color Perception↗
PubMed1998

Effect of remifentanil on the auditory evoked response and haemodynamic changes after intubation and surgical incision.

We have observed the effect of intubation and incision, as measured by the auditory evoked response (AER) and haemodynamic variables, in 12 patients undergoing hernia repair or varicose vein surgery who received remifentanil as part of either an inhaled anaesthetic technique using isoflurane or as part of a total i.v. technique using propofol. Anaesthesia was induced with remifentanil 1 microgram kg-1 and propofol, neuromuscular block was achieved with atracurium 0.6 mg kg-1 before intubation, and anaesthesia was maintained with a continuous infusion of remifentanil in combination with either a continuous infusion of propofol or inhaled isoflurane. The AER and haemodynamic variables were measured before and after intubation and incision. The effects of intubation and incision on the AER and haemodynamic variables were not significantly different between the remifentanil-propofol and remifentanil-isoflurane groups. However, the study had a low power for this comparison. When the data for the two anaesthetic combinations were pooled, the only significant effects were increases in diastolic arterial pressure and heart rate immediately after intubation; these were not seen 5 min after intubation. There were no cardiovascular responses to incision. There were no significant changes in the AER after intubation or incision.

Analgesics, Opioid↗
PubMed1997

Contingent color aftereffects: reassessing old conclusions.

Although there is considerable evidence supporting an associative interpretation of contingent color aftereffects, there are data that appear inconsistent with this interpretation. New findings from seven experiments are presented indicating that, contrary to earlier claims, contingent color aftereffects are observed after induction with (1) single orthogonal black bars on colored backgrounds, (2) geometric forms, and (3) two orthogonal grids of the same color. The results of these experiments are relevant to an associative interpretation of contingent color aftereffects, as well as to assessing alternative interpretations of the phenomenon.

Adult↗
PubMed1997

Isoluminance and contingent color aftereffects.

In the typical induction of the orientation-contingent color aftereffect (CCAE), the stimuli are composed of elements that differ in both color and luminance. Three experiments are reported that show that chromatic contrast between stimulus elements is insufficient for the induction of the orientation-CCAE and that luminance contrast is necessary. These experiments expand on previous research concerned with the role of luminance contrast in the induction of orientation-CCAEs by eliminating alternative explanations.

Adult↗
PubMed1995

An associative interpretation of the indirect McCollough effect.

Following an induction procedure in which a coloured grid is alternated with a square of a complementary colour, subjects report colour after-effects on both the grid orientation present during induction and the orthogonal non-induced grid orientation. The after-effect reported on the induced grid orientation is called the McCollough effect (ME). The after-effect reported on the non-induced grid orientation is called the indirect ME. There is evidence that the ME represents an instance of Pavlovian conditioning. The present results support a conditioning interpretation of the indirect ME and are inconsistent with interpretations of the indirect ME that attribute the phenomenon to special orthogonal coding mechanisms within the visual system.

Adult↗
PubMed1994

Scanning and form-contingent color aftereffects.

G. K. Humphrey, A. M. Herbert, L. A. Symons, and S. Kara (1994) and J. Broerse and P. Grimbeek (1994) suggested that the form-contingent color aftereffect reported by S. Siegel, L. G. Allan, and T. Eissenberg (1992) would not be obtained if Ss were instructed to scan the induction and assessment forms. The authors present data from Ss who were instructed to scan the forms. These scanning Ss displayed aftereffects that were no different from those described earlier by Siegel et al. Scanning Ss do display spatiotopic contingent color aftereffects.

Color Perception↗
PubMed1994

A new temporal illusion or the TOE once again?

Recently, Nakajima, ten Hoopen, and van der Wilk (1991) and Nakajima, ten Hoopen, Hilkhuysen, and Sasaki (1992) described what they believed to be a new illusion of auditory time perception. They reported that the perceived duration of a temporal interval was influenced by an immediately preceding or succeeding temporal interval. The influence of a neighboring temporal interval on perceived duration is not a new illusion, however, but is another demonstration of the time-order error.

Acoustic Stimulation↗
PubMed1993

Human contingency judgments: rule based or associative?

The study of the mechanism that detects the contingency between events, in both humans and nonhuman animals, is a matter of considerable research activity. Two broad categories of explanations of the acquisition of contingency information have received extensive evaluation: rule-based models and associative models. This article assess the two categories of models for human contingency judgments. The data reveal systematic departures in contingency judgments from the predictions of rule-based models. Recent studies indicate that a contiguity model of Pavlovian conditioning is a useful heuristic for conceptualizing human contingency judgments.

Conditioning, Classical↗
PubMed1993

McCollough effects as conditioned responses: reply to Dodwell and Humphrey.

P. C. Dodwell and G. K. Humphrey (1990) criticized the Pavlovian conditioning analysis of the McCollough effect, claiming that it was conceptually flawed and that it did not assign the McCollough effect any useful function. In this article, it is suggested that the error-correction interpretation that Dodwell and Humphrey proposed as an ostensible alternative to the conditioning interpretation can be subsumed by the conditioning interpretation. Furthermore, the conditioning interpretation does ascribe a useful function to the McCollough effect.

Attention↗
PubMed1992

The associative basis of contingent color aftereffects.

According to a conditioning analysis of the orientation-contingent color aftereffect (McCollough effect, ME), orientation stimulus (grids) become associated with color. Contrary to this interpretation are reports that simple forms cannot be used to elicit illusory color and that the ME is not degraded by decreasing the grid-color correlation. The present results indicate: (a) Form stimuli can contingently elicit color aftereffects; (b) even a non-patterned stimulus--the lightness of a frame surrounding a colored area--can contingently elicit color aftereffects; (c) this frame lightness-contingent aftereffect, like the ME, persists for at least 24 hr; and (d) the frame lightness-contingent aftereffect can be used to demonstrate that correlational manipulations affect the ME, as they affect other types of conditional responses.

Adult↗
PubMed1991

Characteristics of the indirect McCollough effect.

Induction of contingent color aftereffects with a single chromatic grid sometimes results in an illusory color on a grid different from the one presented during induction. Such illusory color, contingently elicited by a noninduced grid, has been termed the indirect McCollough effect (indirect ME). We show that the indirect ME occurs only when the color complementary to the grid color is present during induction (either physically present or as a color afterimage), and that the indirect ME is seen only on gratings that are orthogonal to the induction orientation. These findings are in accord with the account of the indirect ME proposed by Humphrey, Dodwell, and Emerson (1989). We also show that characteristics of the indirect ME (seen following one-grid induction), both on induced and orthogonal orientations, are similar to those observed with the direct ME (seen following the usual two-grid induction procedure). Both procedures result in contingent aftereffects that display substantial retention and that do not display interocular transfer.

Adult↗
PubMed1990

Spatial contingency and the McCollough effect.

On the basis of a conditioning analysis of the orientation-contingent color aftereffect (McCollough effect, ME), orientation stimuli become associated with simultaneously presented chromatic stimuli. This account suggests that decreasing the contingency between the grid orientation and color should decrease the strength of the aftereffect. Results of previous research indicate that decreasing the temporal contingency (by presenting homogeneous chromatic stimuli between presentations of chromatic grids) does not decrease the ME. However, it has been suggested that the appropriate contingency-degradation procedure would involve decreasing spatial (rather than temporal) contingency. That is, the illusion should be attenuated by extending the color beyond the confines of the grid. Contrary to this hypothesis, the results of the present experiments provide no evidence that decreasing the spatial contingency between grid and color decreases the ME; rather, the aftereffect is increased by such a manipulation.

Adult↗
PubMed1989

The Cyclops 33 radiation thermometer. An appraisal for use in anaesthesia.

The Cyclops 33 is a portable infrared radiation thermometer. It has many potential advantages over existing thermometers in anaesthetic practice. The technical details are described and the benefits over other instruments discussed. This apparatus offers considerable scope for advance in the field of thermometry in anaesthesia.

Anesthesiology↗