Pharmacokinetics of physostigmine in man following a single application of a transdermal system

1. The pharmacokinetics of physostigmine were investigated in a three-way cross-over design in six healthy, male volunteers comparing a physostigmine transdermal system (PTS), an oral solution and an i.v. infusion. 2. A single application of the patch over 24 h produced detectable plasma drug concentrations after a mean lag-time of 4 h. Thereafter, the drug was absorbed continuously from the PTS and putative therapeutic plasma concentrations were measured over approximately 18 h. 3. A mean absolute bioavailability of 36% was determined for the transdermal system and 3% for the oral solution. In comparison with the oral solution, interindividual variability of pharmacokinetics was less with the PTS. 4. The mean amount of physostigmine released from the transdermal system after 24 h was 5.7 mg. Because of extensive metabolism, only 2.2 mg of physostigmine were detected systemically. 5. After removing the PTS, the mean apparent half-life of elimination was 4.9 h, compared with 0.5 h for the i.v. infusion. This indicates continued drug absorption from a skin depot. 6. Physostigmine was well tolerated by the volunteers. With the PTS, a mild erythema was observed at the area of application, disappearing within a few hours.

A multiple-dose safety trial of eptastigmine in Alzheimer's disease, with pharmacodynamic observations of red blood cell cholinesterase

A placebo-controlled multiple dose study was conducted to evaluate the safety, tolerability, and pharmacodynamics of multiple dose levels of eptastigmine in 25 patients with probable Alzheimer's disease (AD). Twenty patients (12 M, 8 F; mean age 74, range 57-84) were randomized to receive 12mg (N = 3), 20mg (N = 6), 28mg (N = 6) or placebo (N = 5) tid on a double-blind basis for 14 days, followed by seven days of single blind placebo, in successively rising dose groups. All patients completed the study without intolerable or severe adverse events. All doses significantly (p < 0.001) reduced peak and trough RBC cholinesterase (AChE) activity as compared to baseline. Percent inhibition for Day 14 peak and trough RBC AChE peak and trough values, respectively, appeared proportional to dose: 18% and 21% (12mg); 36% and 35% (20mg); 40% and 44% (28mg). In order to determine the maximum tolerated dose of eptastigmine, an additional single-blind study was performed in five patients (2 M, 3 F; mean age 78, range 72-80) utilizing a rising dose schedule of eptastigmine (N = 4) or placebo (N = 1), starting with the previously tolerated 28mg tid dose and increasing by 4mg tid up to a potential maximum of 56mg tid. Dose-limiting adverse events occurred requiring discontinuation of medication in one patient at 48mg tid and two patients at 52mg tid; RBC AChE inhibition was proportional to dose, with peak values up to 70% inhibition at 48mg tid. The maximum tolerated dose of 48mg tid was identified as a basis for potential Phase II multicenter efficacy trials.

Oral physostigmine and impaired memory in adults with brain injury

The purpose of this study was to examine the effects of physostigmine, a cholinergic agonist, on memory loss after traumatic brain injury (TBI), as compared to placebo or scopolamine, a cholinergic antagonist, using a double-blind, placebo-controlled design. Each subject received each active drug and placebo. Neuropsychological measures (Wechsler Memory Scale I and II, Selective Reminding Test, Trail-Making Test, Parts A and B, Digit Symbol, and Memory Questionnaire) and measures of clinical balance were completed at baseline, after each drug phase, and at 1 month follow-up. Thirty-six subjects completed the study with results showing an improvement in memory scores in 44% of subjects (responders) while taking oral physostigmine. The most sensitive measure was the Selective Reminding Test, specifically Long-term Storage. The impact of drugs on standing balance as compared to placebo was improved standing time in the responders: (1) with physostigmine when standing tandem with eyes closed (p < 0.05), and (2) with scopolamine when standing on one foot with eyes closed (p < 0.05). Results support the potential benefit of cholinergic agonists on memory after TBI and the need for further research of possible clinical markers for the drug.

Effects of direct and indirect acetylcholine receptor agonists on growth hormone secretion in humans

Cholinergic pathways in the central nervous system positively influence growth hormone (GH) secretion. In fact pyridostigmine, a cholinesterase inhibitor, enhances both basal and GH-releasing hormone (GHRH)-induced GH secretion while, conversely, pirenzepine, an antagonist of muscarinic M1 receptors, inhibits the GH response to GHRH and to other physiological and pharmacological stimuli. The effect of the cholinergic system on GH secretion probably takes place via inhibition of the release of endogenous somatostatin. In this study in 36 normal adults (26 males and 10 females, age 22-35 years) we compared the effects of three cholinesterase inhibitors (pyridostigmine, 120 mg p.o., n = 19; neostigmine, 10 micrograms/kg i.v., n = 6; physostigmine, 12.5 micrograms/kg i.v., n = 6) and bethanechol, a direct muscarinic receptor agonist that is mainly active on muscarinic M3 receptors (25 micrograms/kg i.v., n = 5), on both basal and GHRH (1 microgram/kg i.v.)-stimulated GH secretion. Pyridostigmine, neostigmine and physostigmine induced a significant GH increase (peak vs. basal levels, mean +/- S.E.: 10.4 +/- 1.6 vs. 0.6 +/- 0.2 micrograms/l, P = 0.0001; 13.3 +/- 1.2 vs. 0.5 +/- 1.1 micrograms/l, P = 0.004; and 14.9 +/- 3.1 vs. 2.7 +/- 1.1 micrograms/l, P = 0.025;, respectively). These drugs also induced a similar potentiation of the GH response to GHRH (peak: 48.3 +/- 5.6 vs. 16.2 +/- 2.2 micrograms/l, P = 0.0001; 49.2 +/- 2.2 vs. 19.9 +/- 5.1 micrograms/l, P = 0.006; and 76.9 +/- 12.4 vs. 18.1 +/- 5.3 micrograms/l, P = 0.001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Transdermal physostigmine in the treatment of Alzheimer's disease

Physostigmine has been reported to improve the memory function of some patients with Alzheimer's Disease (AD). However, the drug has a short half-life and a narrow therapeutic window. To overcome these impediments, we developed a continuous transdermal delivery system and tested it for 2 weeks in 12 AD inpatients, using a single-blind design. No major adverse effects were recorded in any of the patients. Physostigmine plasma concentrations were relatively stable (0.56 +/- 0.10 ng/ml) and correlated well with blood acetylcholinesterase inhibition. Six of the 12 patients reported improved vigilance and concentration, and also had higher scores in all four neuropsychological tests employed (Mini Mental State examination, Short Mental Test [SMT], Wechsler's Memory Scale [WMS], and Buschke's Selective Reminding Test). The performance of two additional patients improved in only two tests (SMT and WMS). Transdermal delivery of physostigmine appears to be safe and may be useful for the treatment of a subset of AD patients.

Chromodacryorrhea in rats: absence following soman poisoning

Chromodacryorrhea is the secretion of so-called "bloody tears" from the harderian gland which nearly circumscribes the eye within the bony orbit. Direct-acting cholinergic agonists such as oxotremorine, carbachol, and pilocarpine caused chromodacryorrhea but nicotine did not. Atropine blocked chromodacryorrhea induced by systemic administration of direct-acting cholinergic agonists. Thus, chromodacryorrhea appears to be a muscarinic receptor-related event. Soman (pinacolyl methylphosphonofluoridate), a potent irreversible inhibitor of acetylcholinesterase which increases the synaptic concentration of the neurotransmitter acetylcholine, did not induce chromodacryorrhea in rats. Similarly, physostigmine, a tertiary, carbamate acetylcholinesterase inhibitor, did not induce chromodacryorrhea. In vivo soman-induced inhibition of harderian gland acetylcholinesterase was independent of the soman dose and the inhibition was significantly less than brain acetylcholinesterase. In vitro soman-induced inhibition of harderian gland acetylcholinesterase was not significantly different from that of diaphragm acetylcholinesterase. The lack of inhibition of acetylcholinesterase in the harderian gland does not appear to be due to a difference in sensitivity to inhibition by soman. The distribution of the various molecular forms of acetylcholinesterase between the diaphragm and harderian gland was different. There was a great deal more of the 4S form of acetylcholinesterase in the harderian gland than in the diaphragm. The lack of the following, inhibition of harderian gland acetylcholinesterase and elevation of the synaptic concentration of acetylcholine, could explain the absence of chromodacryorrhea following soman poisoning. The discrepancy between the significant soman-induced inhibition of brain acetylcholinesterase and the lack of inhibition of harderian gland acetylcholinesterase allows one to speculate that there may be a very efficient scavenger of soman present in the rat harderian gland.

Trial of oral physostigmine in amyotrophic lateral sclerosis

We evaluated a double-blind, placebo-controlled, and double-crossover trial of oral physostigmine salicylate for a 9-month period in 13 of 25 patients with sporadic amyotrophic lateral sclerosis (ALS). A large dropout rate of 48% was secondary to eight deaths and four exclusions attributed to the incapability to swallow the tablets (physostigmine) and capsules (lecithin) or to attend the clinic. Parameters used for assessment of the drug efficacy included body weight, ALS score, Jamar grip strength, forced vital capacity, and maximum voluntary ventilation. It revealed slight benefit in reduced loss of grip strength compared with the pretrial and placebo periods. However, the rates of decline for body weight, ALS score, forced vital capacity, maximum voluntary ventilation, and megascore did not differ significantly between the pretrial, placebo, and physostigmine periods. We therefore concluded that overall no significant alteration in the clinical course was gained by oral physostigmine therapy in the 13 patients with ALS who were included in this study.

Safety and efficacy of oral physostigmine in the treatment of Alzheimer disease

Results of therapeutic trials with physostigmine in the treatment of Alzheimer disease (AD) have been inconsistent and controversy persists concerning safety and efficacy. In a double-blind, placebo-controlled, crossover study, patients received 6 weeks of oral physostigmine (OP) and placebo in random order. Twenty-nine patients with AD received as much as 16 mg/day of OP and were assessed with neuropsychological and functional measures. No significant cardiac side effects were noted, though other systemic adverse effects were noted, requiring dose reduction in four patients. There was a slight but significant improvement (12%) in performance on the selective reminding test with physostigmine and the memory performance was correlated with dosage. This improvement compares favorably with the 15% decrease in scores seen in an untreated comparison cohort followed for an equivalent time period. There was a trend toward an improvement in communication and a reduction in memory complaint. These results suggest that oral physostigmine is safe and may improve memory in AD.

A pilot study of oral physostigmine plus yohimbine in patients with Alzheimer disease

Effective symptomatic treatment of Alzheimer's disease (AD) may require a combination of agents that augment cholinergic as well as noradrenergic neurotransmission. We conducted a pilot study of physostigmine plus oral yohimbine challenge in AD. Ten patients were enrolled in a 12-day double-blind protocol. Each patient received placebo q2h while awake for 5 days, followed by physostigmine 2 mg q2h while awake for 7 days. During each of these drug conditions, yohimbine challenges were administered at oral doses of 10 and 20 mg in a placebo-controlled manner. There was no significant improvement in Alzheimer's Disease Assessment Scale test performance for six patients for whom complete cognitive data were obtained for the 6 challenge days. Nine patients tolerated the protocol with no clinically significant changes in blood pressure, pulse, or electrocardiogram (ECG), and no cardiovascular, gastrointestinal, or autonomic toxicity. One patient complained of chest discomfort associated with tachycardia, a modest rise in blood pressure, and had t-wave inversion in a single precordial lead. These signs and symptoms resolved within a few hours. Serial ECG tracings and cardiac enzymes revealed no evidence of myocardial injury. This pilot study did not reveal major cognitive improvement with this regimen, but underscores the importance of careful cardiovascular monitoring during future combined cholinergic-noradrenergic therapies in AD.

A strategy of "combination chemotherapy" in Alzheimer's disease: rationale and preliminary results with physostigmine plus deprenyl

Although the central cholinergic deficits are still considered to be of primary importance in Alzheimer's disease, there is great need for an expansion of the pharmacological approach in this illness beyond the simple cholinergic replacement hypothesis. This report focuses on the concept of "combination chemotherapy" in Alzheimer's disease as the next generation of therapeutic strategies. Based on earlier positive findings in Alzheimer patients with the monoamine oxidase B inhibitor, 1-deprenyl, the authors speculate that a combination of physostigmine, the short-acting cholinesterase inhibitor, and 1-deprenyl might be more beneficial than either agent alone. The authors outline a sample paradigm for such combination studies, report preliminary data on the first 16 Alzheimer subjects to have received an initial combination of physostigmine and deprenyl, and point to other possible "combination chemotherapy" strategies for future study.

Semen retrieval in spinal cord injured men

A fertility programme for spinal cord injured men has been in progress for nearly 5 years. Thirty eight men have been treated in this programme. Electroejaculation, vibration ejaculation and subcutaneous physostigmine have all been used successfully to obtain semen. Semen has been obtained from 21 of 24 men with a lesion at T8 or above, and from 4 of 11 men with lesions below T10. There have been 8 pregnancies from 6 couples.

Good-quality semen recovered from a paraplegic man with physostigmine salicylate treatment. A case report

A subcutaneous injection of physostigmine was employed to treat paraplegic anejaculation. The sperm motility was greater than in previously reported studies in which electroejaculation techniques were used for seminal emission.

Observations on the physostigmine syndrome in patients with Alzheimer's disease

The authors present two patients with Alzheimer's disease who each received a single intravenous dose of physostigmine. Subjective complaints and mood changes were disproportional with objectively verified physiological side effects. Such observations may contribute to an understanding of affective disorders and should receive more attention in future studies of cholinesterase inhibitors.

Comparison of DuP 996, with physostigmine, THA and 3,4-DAP on hypoxia-induced amnesia in rats

DuP 996, 3,3-bis(4-pyrindinylmethyl)-1-phenylindolin-2-one, physostigmine (PH), tetrahydroaminoacridine (THA) and 3,4-diaminopyridine (3,4-DAP) were compared for their ability to protect against hypoxia-induced performance deficits in a passive avoidance (PA) task. The ability to retain PA response was found to decrease as the oxygen concentration decreased with the largest retention deficit occurring at 6.5% oxygen. DuP 996 (0.01-0.1 mg/kg SC), 3,4-DAP (0.1-10.0 mg/kg SC), THA (0.3-5.0 mg/kg SC) and PH (0.001-0.1 mg/kg SC) administered one minute after PA training produced dose-dependent increases in retention latencies following exposure to 6.5% oxygen. In comparing each compound for side effects, DuP 996 induced tremor and mortality at 10 and 40 mg/kg SC, respectively, and PH at 0.3 and 0.8 mg/kg SC, respectively. With PH the 0.3 mg/kg SC dose also produced hypersalivation and a decrease in lift strength. THA produced tremor and mortality at 6.0 and 40 mg/kg SC, respectively, and 3,4-DAP at 50 and 200 mg/kg SC, respectively. 3,4-DAP also produced chromodacryorrhea and hypersalivation at 50 mg/kg SC. Dividing the dose necessary to produce mortality by the highest effective dose active in the hypoxia test yielded a safety ratio for DuP 996 of 400, for 3,4-DAP 20, for PH 8, and for THA 8, showing a greater safety margin for DuP 996 than the other cholinergic agents. These results suggest that DuP 996 may be of use in the treatment of diseases associated with cognitive impairment and may have a greater safety margin than other cholinergic agents.

Physostigmine, tacrine and metrifonate: the effect of multiple doses on acetylcholine metabolism in rat brain

The effects of two consecutive intramuscular doses of three cholinesterase inhibitors (physostigmine, tetrahydroaminoacridine and metrifonate) were compared in rats. The results revealed major differences in biochemical effects on the brain of the rat including the extent and duration of inhibition of cholinesterase, inhibition of release of acetylcholine and increase in levels of acetylcholine. Side effects were also markedly different in the time of appearance, duration and severity. These results suggest that there are significant differences in the mechanisms of action of various cholinesterase inhibitors. Since all three cholinesterase inhibitors are currently used in the experimental treatment of Alzheimer's disease, these findings have potential implications for the symptomatic therapy of these patients.

Long-term administration of oral physostigmine in Alzheimer's disease

Minimal short-term benefits with oral physostigmine have been reported in Alzheimer's disease. We examined long-term oral physostigmine therapy in 14 patients with probable Alzheimer's disease in an extended double-blind crossover trial in which they received physostigmine for five intervals of 4 to 6 weeks in length and placebo for one interval determined at random. At each interval a Selective Reminding Test was administered and three indexes were examined: total recall, long-term recall, and intrusions. As a group, patients' memory test scores were significantly better during the drug period. Two patients who previously had performed worse on drug than on placebo in a short-term trial continued to do so. Nine of the remaining 12 patients performed better on two or more measures on physostigmine compared with placebo. In some cases scores improved up to 50% over placebo values. This improvement was not predicted by response to medication in the earlier short-term trial. Seven patients completed an additional six-interval crossover trial. All but one continued to have improved performance with oral physostigmine and, in grouped data, memory measures remained significantly improved. These results suggest that long-term administration of physostigmine in Alzheimer's disease may be more effective than short-term. This benefit can be sustained for up to a year in some patients.

Carbamate-induced performance and thermoregulatory decrements restored with diazepam and atropine

When rats (500 g, male) are exercised on a treadmill, pretreatment with the carbamate physostigmine reduces endurance capacity (run time, RT) and increases the rate of rise of core temperature (heating rate, HR). Because physostigmine is a potential nerve agent pretreatment drug, our objective was to determine whether pharmacological intervention could reverse these decrements in performance and thermoregulation. The following drugs were administered separately via tail vein: vehicle-control (C), atropine (200 micrograms.kg-1, A), diazepam (500 micrograms.kg-1, D), and physostigmine (200 micrograms.kg-1, PH). After drug administration, rats were run (11 m.min-1, 6 degrees elevation, Ta = 26 degrees C) to exhaustion. PH administration resulted in reduced RT (41 min PH vs. 53 min C, p less than 0.05) with greater HR (0.090 degrees C.min-1 PH vs. 0.057 degrees C.min-1 C, p less than 0.01) than control rats. However, when A and D were also given to PH treated rats, the RT and HR were restored to control levels. Further, A and D without PH improved RT and HR (82 min, 0.047 degrees C.min-1) over control levels. Serial administration of an anticholinergic, an anticonvulsant, and an anticholinesterase resulted in no significant change in performance from control levels.

Effects of oral physostigmine in Alzheimer's disease

Previous studies of oral physostigmine in the treatment of Alzheimer's disease have: (1) assumed physostigmine is effective only in mildly affected patients; (2) relied on an initial "dose-finding" phase to determine the most effective dose and excluded nonresponders; and (3) primarily assessed memory. We examined the response of 22 patients to six different daily dosages of oral physostigmine, using selective reminding tests that were administered twice daily. Nine patients had a "best" dose/day (mode = 13 mg/day), which was used in a subsequent double-blind crossover study. The other 13 were given the highest tolerated dose. The selective reminding test and a full neuropsychological battery were given during the drug and placebo periods. As a group, the 22 patients improved significantly on the Wechsler Adult Intelligence Scale-Revised Digit Symbol subtest and a shape cancellation task (p less than 0.05). Nine patients showed improved performance on the selective reminding test during physostigmine treatment, and 9 showed no response; 4 patients performed better during placebo treatment. Dose finding did not help in predicting response in the crossover study; only 2 of the 9 who showed improvement had a best dose. Dementia severity did not predict crossover response. This suggests that: (1) physostigmine as administered had no pronounced effect on memory in Alzheimer's disease; (2) oral physostigmine produces no greater benefits on memory in mildly than in moderately demented patients; (3) response in a dose-finding phase does not predict response in double-blind crossover; and (4) Digit Symbol and cancellation tasks may be more sensitive than memory tests to the effects of oral physostigmine.

[Therapy of the anticholinergic syndrome in poisonings]

Underlying literature and taking into consideration own experiences in the anticholinergic syndrome the following view is taken: Physostigmine salicylate is the remedy of choice for the treatment of the anticholinergic syndrome and altogether causes only slight side effects. While for differential-diagnostic reasons the application is recommended under hospital conditions, the pre-hospital application is to be estimated as problematical. The improvement of the clinical symptoms under the influence of physostigmine salicylate must not lead to the neglect of the control of the patient. A differentiated use of physostigmine salicylate is necessary, and it cannot be regarded as "universal antidote" in intoxications caused by central-nervous effective substances.