Data provided by Applied Health
side effects, nutrient depletions, herbal interactions and health notes:
• Smooth pursuit eye movement (SPEM) and antisaccade deficits are observed in the schizophrenia spectrum and have been used to study the pathophysiology as well as the genetic basis of this condition. The neurotransmitter acetylcholine has been implicated in a number of cognitive processes thought to underlie SPEM and antisaccade performance. This study investigates effects on eye movements of procyclidine, an anticholinergic drug often administered to schizophrenic patients. A total of 13 patients completed a double-blind placebo-controlled crossover design, receiving 15 mg procyclidine and placebo. Seven participants received procyclidine first and placebo second, six participants were tested in the reverse order. SPEM and antisaccade (as well as fixation and prosaccade) eye movements were recorded using infrared oculography. Results showed that procyclidine overall, relative to placebo, mildly worsened SPEM performance, as indicated by nonsignificantly reduced gain (p=0.08) and increased frequency of intrusive anticipatory saccades during pursuit1
• A significant interaction of group and order of administration indicated that procyclidine increased the rate of antisaccade reflexive errors only when administered first; the opposite pattern was observed when placebo was administered first, likely due to the operation of practice effects at second assessment. These findings indicate that acute administration of a clinically relevant dose of procyclidine leads to mild impairments in eye movement performance in schizophrenic patients, suggesting the need to consider this compound in oculomotor studies in schizophrenia. The action of this anticholinergic drug on oculomotor performance is consistent with the hypothesized role of the cholinergic system in the cognitive mechanisms of attention and working memory, processes thought to underlie SPEM and antisaccade performance. Effects of order of administration and practice on the antisaccade task suggest that these factors need to be taken into consideration in future pharmacological studies.2
• Prepulse inhibition (PPI) of the startle response refers to an attenuation in response to a strong stimulus (pulse) if this is preceded shortly by a weak non-startling stimulus (prepulse). Patients with schizophrenia have repeatedly been found to show reduced PPI when compared to healthy people. Anticholinergic drugs are often used to control extrapyramidal symptoms induced by antipsychotic medication in schizophrenic patients. Antipsychotic medication, in particular with atypical drugs, has been shown to improve a range of cognitive functions and normalize PPI deficits in schizophrenia, whereas anticholinergic drugs disrupt cognitive functions in both normal and schizophrenic populations and also impair PPI in experimental animals. No previous study has investigated the effects of anticholinergic drugs on human PPI. OBJECTIVES: This study determined the effects of procyclidine, an anticholinergic drug, on PPI in healthy male volunteers, employing a double-blind placebo-controlled cross-over design. METHODS: Subjects underwent testing for PPI on two occasions: once after the oral administration of a placebo and once after the oral administration of procyclidine in two separate experiments. Experiment 1 examined the effects of 10 mg procyclidine, whereas experiment 2 examined the effects of 15 mg procyclidine. RESULTS: Procyclidine at a 10 mg dose, as compared to placebo, had no effect on PPI, but caused impairments at a 15 mg dose. In both experiments, procyclidine reduced response amplitude over the pulse-alone trials and heart rate 1-2 h post-administration. CONCLUSIONS: PPI of the human acoustic startle response is modulated by procyclidine. The use of anticholinergics needs to be considered in PPI studies in schizophrenia.3
• Due to muscarinic effects on bronchial smooth muscle, isolated arecoline alkaloid challenge causes bronchoconstriction and therefore may reduce the effectiveness of some classes of antiasthmatic medications. Very few common medicinal herbs have overtly cholinergic constituents that produce overall physiological parasympathomimetic action. The exceptions are restricted herbs, poisons, or foods not generally used in herbal medicine, such as the pilocarpine-containing Pilocarpus spp. (Jaborandi) and muscarine from Amanita muscaria and related toxic mushroom species. The Asian masticatory spice Areca catechu contains the muscarinic alkaloid arecoline, which is also nicotinic at higher doses. Areca is not used therapeutically in Western herbal medicine although the isolated alkaloids have been shown to cause bronchoconstriction and may exacerbate extrapyramidal effects of neuroleptic drugs. Several western herbs are considered "parasympathomimetic-like" by herbalists primarily because of cardiovascular effects that resemble muscarinic cholinergic activity (hypotension, bradycardia). The pharmacology of these agents is either unknown, or results from complex mechanisms other than direct muscarinic agonism. For example, the veratrum alkaloids of Veratrum spp. (Liliaceae) have some cholinergic activity but their predominant bradycardic and hypotensive actions are more due to sodium channel blocking.4
• Individuals prone to asthma, and those taking asthma medications should avoid excessive consumption of Areca catechu (Betel Nut). Betel nut is little used in Western herbal medicine, although large amounts are consumed in India and South East Asia and it is similarly consumed by ethnic populations from these cultures now resident in the West.5
• Deahl reported two cases of schizophrenic patients maintained on depot procyclidine developing severe extrapyramidal symptoms (tremor, stiffness, akithesia) following excessive betel nut consumption.6
References1 Psychopharmacology (Berl). 2001 Mar;154(3):221-9. PMID: 12942142 [PubMed - indexed for MEDLINE
2 Psychopharmacology (Berl). 2001 Mar;154(3):221-9. PMID: 12942142 [PubMed - indexed for MEDLINE
3 PMID: 11351929 [PubMed - indexed for MEDLINE] Psychopharmacology (Berl). 2001 Mar;154(3):221-9.
4 Taylor RFH, et al. Lancet 1992;339:1134-1136
5 Deahl M. Mov Disord 1989;4:330-333
6 Deahl M. Mov Disord 1989;4:330-333
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The information in Drug Watch is provided as a courtesy to NewsTarget readers by Applied Health Solutions in cooperation with Healthway Solutions. Although the information is presented with scientific references, we do not wish to imply that this represents a comprehensive list of considerations about any specific drug, herb or nutrient. Nor should this information be considered a substitute for the advice of your doctor, pharmacist, or other healthcare practitioner. Please read the disclaimer about the intentions and limitations of the information provided on these pages. It is important to tell your doctor and pharmacist about all other drugs and nutritional supplements that you are taking if they are recommending a new medication. Copyright © 2007 by Applied Health Solutions, Inc. All rights reserved.