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Biomedical subjects

M H Lader

Publications and source records attributed to M H Lader.

At least 19 recordsLinked to original sources
PubMed1998

Differentiating the effects of centrally acting drugs on arousal and memory: an event-related potential study of scopolamine, lorazepam and diphenhydramine.

The degree to which apparent amnesic effects of various centrally acting drugs are secondary to their effects on arousal remains a contentious issue. The present study uses two methods to dissociate memory and arousal effects of the cholinergic antagonist, scopolamine (SP), and the GABA-A/benzodiazepine receptor agonist, lorazepam (LZ). First, it compared their effects to those of an antihistamine, diphenhydramine (DPh), to provide an active control for arousal reduction. Second, it used the same measure--event-related potentials (ERPs)--as as a parallel index of both the arousal and cognitive effects of the drugs. Fifty participants were allocated to one of five parallel treatment groups (0.6 mg SP; 2 mg LZ; 25, 50 mg DPh; placebo). ERPs were recorded during a continuous word recognition task as well as during an "oddball" task. SP, LZ and 50 mg DPh produced a similar profile of effects on certain indices of arousal and on early components of ERPs. However, SP and LZ (but not DPh) produced marked impairments of episodic memory, and this pattern was similar to that on later components of ERPs. Memory impairments by SP and LZ were highly significant on retention in the continuous recognition task and further, no drug effects were found on response bias. Subsequent free recall was similarly very impaired by SP and LOR but not by the antihistamine. We conclude that benzodiazepines and anticholinergic drugs both reduce arousal and induce amnesia, but these effects are not interdependent. Our findings provide strong evidence for a dissociation between the effects on episodic memory and on arousal of these centrally acting compounds.

Adult↗
PubMed1997

Irreversible lithium neurotoxicity: an overview.

Lithium is widely used, and most of its side effects are well established and recognized. Persistent neurologic sequelae or dysfunctions are not common, but they are serious side effects. They usually persist after acute toxicity following accidental or suicidal overdose or during maintenance therapy, when toxicity is more insidious. The irreversible neurologic sequelae are generally cerebellar signs, especially ataxia and dysarthria. Risk factors are sometimes present and recognizable, but more often they are not well identified. Persistent neurologic handicaps greatly reduce the quality of life and are difficult to manage. Lithium toxicity can be avoided by conservative prescribing, care in combining drug therapies, and, above all, educating the patient and caregivers to recognize early signs of the condition. A review of the literature is presented, together with vignettes of a further seven cases.

Adult↗
PubMed1996

Tolerability and safety: essentials in antidepressant pharmacotherapy.

Current antidepressants achieve similar efficacy, with 60% to 80% of patients responding adequately. Clinical response is gradual, and differential response factors are difficult to discern. However, side effect profiles and toxicity vary substantially, so the choice of medication depends primarily on tolerability and safety. Dry mouth is prevalent with tricyclic antidepressants (TCAs), whereas nausea occurs more frequently with a serotonin selective reuptake inhibitor (SSRI). Long-term unwanted effects tend not to be a major problem, with a dropout rate of approximately 5% due to side effects. The relationship between suicidality and antidepressants remains under debate. Many TCAs are highly toxic in overdose whereas the SSRIs appear much safer. Nefazodone is a unique antidepressant with demonstrated efficacy. It is different from other antidepressants because of its two actions in the serotonin system, moderate serotonin selective reuptake blocking properties and direct 5-HT2 antagonism, which also can enhance 5-HT1 neurotransmission. The 5-HT2 antagonist properties may limit serotonin-mediated effects and, as a result, nefazodone may be more anxiolytic than other antidepressants. Nefazodone also moderately inhibits norepinephrine reuptake and blocks alpha 1-adrenergic receptors. The data base on the safety of nefazodone currently comprises approximately 3,500 patients from all research trials, which include controlled trials that allow comparisons of nefazodone treatment with several hundred patients taking TCAs or SSRIs and nearly 900 patients receiving placebo. The most frequent adverse experiences with nefazodone as compared with placebo treatment are nausea (21% vs. 14%), somnolence (19% vs. 13%), dry mouth (19% vs. 13%), dizziness (12% vs. 6%), constipation (11% vs. 7%), asthenia (11% vs. 6%), light-headedness (10% vs. 4%), and amblyopia (blurred vision; 6% vs. 3%). Approximately 12% of nefazodone-treated patients dropped out because of adverse experiences, as compared with 7.4% on placebo, 10.4% on SSRIs, but 21.8% on imipramine after short-term exposure in placebo-controlled trials. Long-term safety data include nearly 1,300 patients; nefazodone was well tolerated. Nefazodone was evaluated in normal subjects by the author and was found to produce less impairment than imipramine and was less likely to interact with alcohol. In summary, nefazodone has a favorable adverse-event profile as compared with the TCAs and a rather different one from the SSRIs. It appears to be safe and well tolerated after both acute and long-term use.

Antidepressive Agents↗
PubMed1992

The effects of alprazolam alone and combined with alcohol on central integrative activity.

The effects of alprazolam 1 mg both alone and in combination with 0.5 g/kg of alcohol were examined on self-ratings of intoxication and measures of central and peripheral activity such as EEG, auditory evoked response, tremor at 90, 150 and 210 min post drug. Forty-eight healthy volunteers were assigned randomly to 4 independent groups who received: alprazolam and placebo drink, alprazolam and alcohol, placebo capsule and alcohol, placebo capsule and placebo drink respectively. Alprazolam decreased the amplitudes of the 3 potentials of the evoked response, decreased activity in the 8-13 Hz and increased activity in the 13.5-26 Hz wavebands of the EEG and decreased the frequency at which fusion was perceived. Alcohol prolonged reaction time and increased tremor. The effects were not always additive and alprazolam was dominant in the combination.

Adult↗
PubMed1989

The effects of alcohol on psychological functions in normal volunteers after 8 days' treatment with pipequaline (PK 8165), diazepam or placebo.

The effects of daily administration for 8 days of 50 mg pipequaline, 10 mg diazepam and placebo were assessed in a double-blind cross-over study with 12 healthy volunteers. This study also tested for an interaction between the drugs and alcohol on the eighth day. Subjective ratings, psychomotor and memory performance were evaluated. Diazepam produced the typical pattern of changes, namely impairments in psychomotor performance and reductions in the retention of newly memorised information. In contrast, the effects of pipequaline were relatively minor. In general, neither drug potentiated the effects of alcohol on performance, only isolated instances of non-additive interactions occurring. Subjective reports revealed that whereas both active drugs increased feelings of calmness, this result was accomplished by pipequaline with considerably less drowsiness, no euphoria and a general absence of the adverse side effects of diazepam.

Adult↗
PubMed1989

Self-report reliability and symptomatology of habitual caffeine consumption.

1. A large body of research on the demography of caffeine use and its potential health consequences has been undermined by the absence of empirical data on the reliability of retrospective self-reports of caffeine consumption. 2. The principal aim of the present study was to use standard bioanalytic method to assess the reliability of subjects' self-reported caffeine use. Saliva samples were obtained from 142 first-and second-year medical students and assayed for caffeine and paraxanthine. 3. Self-reported caffeine use was found to be significantly correlated with salivary caffeine (r = 0.31, P less than 0.001) and paraxanthine (r = 0.42, P less than 0.001), thereby providing qualified support for use of questionnaires to estimate patterns of caffeine consumption. 4. A secondary aim of the study was to extend previous research concerning the symptomatology of caffeine use by examining the association between caffeine exposure and a variety of measures of somatic and psychological health. Caffeine consumption was reliably associated with the self-reported occurrence of somatic symptoms, but not psychological well-being.

Adolescent↗
PubMed1988

The effects on memory of pipequaline, alone or in combination with diazepam.

Pipequaline (PK 8165) is a putative mixed agonist/antagonist at benzodiazepine receptors. The effects of pipequaline and diazepam on memory were assessed in 12 normal volunteers. Diazepam 10 mg or placebo was added to two doses of pipequaline, 50 and 150 mg, or to placebo in a double-blind crossover design. Diazepam produced impairments of episodic memory. In contrast, the effects of pipequaline were minor. Addition diazepam to pipequaline increased drowsiness and general lethargy, with a less marked effect occurring for the higher dose of pipequaline alone. Pipequaline did not antagonise any of the effects of diazepam.

Adult↗
PubMed1987

A controlled comparison of fluoxetine and amitriptyline in depressed out-patients.

Fluoxetine, a selective serotonin uptake inhibitor (mean dose 73 mg each morning) was compared with amitriptyline (mean dose 122 mg at night) in a double-blind study of 64 depressed out-patients. Fifty patients completed the 6-week trial. The drugs did not differ with respect to psychiatrists' ratings, but amitriptyline was slightly superior with respect to patients' ratings. The amitriptyline-treated group had complaints of dry mouth and dizziness on standing; the fluoxetine-treated group of sleep disturbances, nausea, and headaches.

Adult↗
PubMed1986

A case of resistant schizophrenia.

In an era when it is generally believed that the acute symptoms of schizophrenia can be controlled pharmacologically, the case of a young man who has remained almost continuously floridly psychotic for 13 years, despite treatment, is disquieting. Conventional psychiatric treatment appears to be rendered impotent. It is in this context that it may be of interest to report a summary of the proceedings of a Special Problems Conference held at the Institute of Psychiatry on 18 February 1985 to discuss such a case.

Adult↗
PubMed1985

Determination of excitability in human proprioceptive reflexes: analysis and characteristics of EMG thresholds of postural muscle.

In order to derive indirect indices of reflex excitability, human soleus (Sol) H reflex and direct M response threshold intensities (HT, MT) were determined by probit analysis of quantal responses elicited in the surface electromyogram (EMG). Within sessions, HT and MT co-varied with respect to time along a logarithmic time-course, both attaining effectively stable levels after 40-60 min of recording. The pattern of this co-variation was imposed by non-reflex factors, primarily the electrode system employed. Sampling distributions of stable thresholds were positively skewed (median values: HT, 5.20 mA, MT, 6.83 mA), and concurrently determined values were strongly correlated (r = 0.965). The Sol threshold ratio (HT/MT) was largely unaffected by non-reflex factors and was therefore stable within subjects, both within sessions (with respect to time) and between sessions. This ratio was normally distributed (mean = 0.753 +/- 0.079 S.D.). Criteria of indirect indices of reflex excitability are proposed: HT satisfies the criteria applicable to a relative index. However, the characteristics of the threshold ratio permit its use as a powerful absolute index of proprioceptive reflex excitability.

Adolescent↗
PubMed1985

Treatment of affective disorders.

The diagnosis of affective disorders is difficult, especially at mild to moderate levels of severity. Often symptomatic treatment is given in the absence of a clear diagnosis. Antidepressants are often efficacious in helping anxiety symptoms but antianxiety compounds are generally inefficacious in treating depression. Alprazolam is a possible exception and may have both antianxiety and antidepressant properties.

Alprazolam↗