Effect of piracetam on level of consciousness after neurosurgery

Effect of piracetam on the cognitive performance of patients undergoing coronary bypass surgery: A meta-analysis

Cognitive impairments are observed in numerous patients following coronary bypass surgery, and piracetam are nootropic compounds that modulate cerebral functions by directly enhancing cognitive processes. The present meta-analysis was conducted to evaluate the protective effect of piracetam on the cognitive performance of patients undergoing coronary bypass surgery. The relevant studies were identified by searching Medline, EMBASE, PubMed and the Cochrane Library up to June 2013 and the pertinent bibliographies from the retrieved studies were reviewed. Data were selected from the studies according to predefined criteria. The meta-analysis included two randomized control trials involving 184 patients and including the Syndrom-Kurz test (SKT). Findings of the meta-analysis showed that following treatment the change from baseline observed in five SKT subtest scores, conducted with piracetam patients, indicated a significant advantage over those patients that were in the placebo group. The subtests included immediate pictured object recall, weighted mean difference (WMD)=0.91, 95% confidence interval (CI) 0.51–1.31, P<0.00001; delayed pictured object recall, WMD=0.74, 95% CI 0.19–1.28, P=0.008; delayed picture recognition, WMD=0.82, 95% CI 0.31–1.31, P=0.001; immediate word recall, WMD=0.87, 95% CI 0.47–1.28, P<0.0001; and letter interference, WMD=3.46, 95% CI −5.69 to −1.23, P=0.002. These results indicated that piracetam may have been effective in improving the short-term cognitive performance of patients undergoing coronary bypass surgery. High quality, well-controlled and longer randomized trials are required to corroborate this result.

Tolerance of liver transplant patients to strenuous physical activity in high-altitude

Physical functioning is improved after liver transplantation but studies comparing liver transplant recipients with normal healthy people are lacking. How liver (and other organ) transplant recipients tolerate strenuous physical activities is unknown. There are no data on the tolerance of transplant patients at high altitude. Six liver transplant subjects were selected to participate in a trek up Mount Kilimanjaro 5895 m, Tanzania. Physical performance and susceptibility to acute mountain sickness were prospectively compared with fifteen control subjects with similar profiles and matched for age and body mass index. The Borg-scale (a rating of perceived exertion) and cardiopulmonary parameters at rest were prospectively compared with six control subjects also matched for gender and VO2max. Immunosuppression in transplant subjects was based on tacrolimus. No difference was seen in physical performance, Borg-scales and acute mountain sickness scores between transplant and control subjects. Eight-three percent of transplant subjects and 84.6% of control subjects reached the summit (p=0.7). Oxygen saturation decreased whereas arterial blood pressure and heart rate increased with altitude in both groups. The only difference was the development of arterial hypertension in transplant subjects at 3950 m (p=0.036). Selected and well-prepared liver transplant recipients can perform strenuous physical activities and tolerate exposure to high altitude similar to normal healthy people.

Antiepileptic effect of nefiracetam on kainic acid-induced limbic seizure in rats

Nefiracetam is being studied as a novel cognition-enhancing agent; however, it has been suggested from studying its chemical structure that it has a potential anticonvulsive effect. We examined the antiepileptic effect of nefiracetam on kainic acid (KA)-induced seizures. KA was infused into the left basolateral amygdaloid nucleus and focal limbic seizures were induced in 43 male Wistar rats. During status epilepticus, 10, 50, 100 or 200 mg/kg of nefiracetam was intravenously injected. Nefiracetam inhibited KA-induced limbic seizures at doses over 100 mg/kg while it had a sedative effect on the animals. In (14C) deoxyglucose autoradiographic studies, the propagation of seizure-induced hypermetabolic areas was also suppressed dose-dependently. From the results, it was indicated that nefiracetam has an antiepileptic effect and that its application may suppress seizure propagation. Further study is required, whether this agent is available as a novel anticonvulsant.

Modulating effect of the nootropic drug, piracetam on stress- and subsequent morphine-induced prolactin secretion in male rats

1. The effect of the nootropic drug, piracetam on stress- and subsequent morphine-induced prolactin (PRL) secretion was investigated in vivo in male rats, by use of a stress-free blood sampling and drug administration method by means of a permanent indwelling catheter in the right jugular vein. 2. Four doses of piracetam were tested (20, 100, 200 and 400 mg kg-1), being given intraperitoneally 1 h before blood sampling; control rats received saline instead. After a first blood sample, rats were subjected to immobilization stress and received morphine, 6 mg kg-1, 90 min later. 3. Piracetam had no effect on basal plasma PRL concentration. 4. While in the non-piracetam-treated rats, stress produced a significant rise in plasma PRL concentration, in the piracetam-pretreated rats PRL peaks were attenuated, especially in the group given 100 mg kg-1 piracetam, where plasma PRL concentration was not significantly different from basal values. The dose-response relationship showed a U-shaped curve; the smallest dose had a minor inhibitory effect and the highest dose had no further effect on the PRL rise. 5. In unrestrained rats, morphine led to a significant elevation of plasma PRL concentration. After the application of immobilization stress it lost its ability to raise plasma PRL concentration in the control rats, but not in the piracetam-treated rats. This tolerance was overcome by piracetam in a significant manner but with a reversed dose-response curve; i.e. the smaller the dose of piracetam, the higher the subsequent morphine-induced PRL peak. 6. There is no simple explanation for the mechanism by which piracetam induces these contradictory effects. Interference with the excitatory amino acid system, which is also involved in opiate action, is proposed speculatively as a possible mediator of the effects of piracetam.

In search of the mechanism of action of the nootropics: new insights and potential clinical implications

The positive action of nootropics on the memory has up to now primarily been discussed in the context of effects on energy metabolism and cholinergic or glutaminergic neurotransmission. Recent findings have shown that the memory-enhancing effect is steroid-sensitive. Since corticosteroids are potent modulators of gene transcription, it appears possible that the nootropics may exert a modulatory action on protein synthesis. This assumption is supported on the one hand by the fact that the nootropics improve the memory even if they are administered several hours after the learning trial, and on the other hand by the observation that their memory-enhancing effect does not become detectable until 16-24 hours after the treatment and learning trial. Provided the memory-enhancing effect in animal experiments and the therapeutic effect in patients come about by way of the same mode of action, the fact that high levels of corticosteroids suppress the effects of the nootropics could also have clinical implications: in the light of the observation that the majority of Alzheimer patients have elevated steroid levels it could explain why there is always only a small proportion of patients in clinical trials that respond to treatment with nootropics.

The pharmacology of the nootropics; new insights and new questions

Up to now, the memory-enhancing effect of the nootropics has chiefly been investigated in the context of effects on energy metabolism and on cholinergic and glutamatergic neurotransmission. Recent studies have also shown that the effect on memory is steroid-sensitive. The present review article summarizes the available results and discusses them in the context of a new hypothesis on the mechanism of action and with respect to clinical implications.

Aldosterone receptors are involved in the mediation of the memory-enhancing effects of piracetam

The blockade of the memory-enhancing effects of piracetam resulting from adrenalectomy can be abolished by substitution with either corticosterone or aldosterone. However, corticosterone substitution does not reinstate these effects if the aldosterone receptors are blocked by the aldosterone antagonist epoxymexrenon.

Involvement of a steroidal component in the mechanism of action of piracetam-like nootropics

Since adrenalectomy abolishes the memory-enhancing effects of piracetam and its derivatives, oxiracetam, aniracetam and pramiracetam, the question arises whether endogenous steroids play a role in their mechanism of action. We show that inhibition of steroid biosynthesis by aminoglutethimide and blockade of the aldosterone receptors by epoxymexrenone completely suppress the memory-improving effects of the nootropics. These results indicate that steroids, or, more precisely, activities mediated by the aldosterone receptors, might be involved in the mechanism of action of this class of nootropics. Blockade of aldosterone receptors, however, does not block the effects of cholinomimetics on memory, indicating the involvement of another mechanism of action.

Blockade of the nootropic action of piracetam-like nootropics by adrenalectomy: an effect of dosage?

The present experiments demonstrate that the absence of any memory-improving action of nootropics in adrenalectomized animals cannot be ascribed to an effect of dosage. Doses of 1, 10, 100, 1000 and 3000 mg/kg p.o. of piracetam, oxiracetam, aniracetam or pramiracetam are ineffective in adrenalectomized mice.

Do piracetam-like compounds act centrally via peripheral mechanisms?

The pharmacological mechanism of action of the piracetam-like nootropics is still obscure. Their unique feature is that they exert distinct effects on memory, but show hardly any biochemical activity and are practically devoid of toxic effects. Our results indicate that the memory-enhancing action of these substances is dependent on the presence of the adrenals, suggesting that their central effects might be mediated by peripheral mechanisms.

Piracetam in elderly psychiatric patients with mild diffuse cerebral impairment

In a 12-week double-blind study, piracetam at two dose levels (2.4 and 4.8 g/day) was compared to placebo in the treatment of 60 elderly psychiatric patients with mild diffuse cerebral impairment, but no signs of focal brain lesion. The psychiatric illness, schizophrenia or affective disorder, of patients selected was in remission at the time of the study. Monthly evaluations by the nurse revealed that piracetam improved overall functioning, particularly alertness, socialization, and cooperation, relative to the control group. Patients treated with 2.4 g/day piracetam also showed significant improvement in scores for the full IQ and the memory quotient on the Wechsler Adult Intelligence and Memory Scales; greater response was seen in those with lower initial scores. Piracetam at 4.8 g/day had a more rapid onset of action on behavioral variables than 2.4 g/day, but its therapeutic effect tended to diminish at 12 weeks, possibly as the result of overstimulation. Piracetam did not appear to interfere with concomitant psychotropic maintenance medication or affect the psychiatric illness itself.

Effects of piracetam on brain monoamine metabolism and serum prolactin levels in the rat

Levels of monoamine metabolites in three different regions of the rat brain were determined following treatment with piracetam (0.5 and 5 g/kg, i.p.). The concentration of prolactin in serum was also measured. Piracetam, at 5 g/kg, increased the levels of dihydroxyphenylacetic acid, homovanillic acid and 3-methoxy-4-hydroxyphenylethylene glycol, whereas 5-hydroxyindoleacetic acid was unaffected. The drug also increased prolactin concentrations in serum. The level of dopamine was unchanged in the olfactory tubercle and the striatum. These effects are different from those obtained with amphetamine-like drugs. The results would seem to indicate that piracetam accelerates brain catecholamine (CA) turnover via a blockade of CA receptors, as suggested for neuroleptic drugs. This effect could be responsible for the therapeutic action of piracetam on psychotic symptoms in psycho-organic disorders of old age. A blockade of brain CA receptors by piracetam is not compatible with facilitated learning, which seems to be mediated via other neuron systems than CA pathways.