Trichlorfon-induced haematological and biochemical changes in Cyprinus carpio: ameliorative effect of propolis.

Trichlorfon is among the most commonly used products to treat fish parasites in aquaculture. We investigated the effectiveness of propolis in alleviating the toxicity of trichlorfon on haematological and oxidant/antioxidant parameters in carp Cyprinus carpio. Fish were exposed to sublethal concentrations (11 and 22 mg l-1) of trichlorfon, and propolis (10 mg kg-1 of fish weight) was simultaneously administered. At the end of 14 d administration, blood and tissue (liver, kidney, gill) samples were collected. Haematological changes (red and white blood cell count, haemoglobin concentration, haematocrit level and erythrocyte indices: mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration) were determined in the blood samples, while antioxidant parameters (malondialdehyde and reduced glutathione levels and superoxide dismutase, catalase and glutathione peroxidase activities) were evaluated in the liver, kidney and gill samples. Trichlorfon led to negative alterations in the haematological and antioxidant parameters investigated. The administration of propolis alleviated this effect and suggests that fish treated with trichlorfon improve their physiological status when fed a propolis-supplemented diet.

Intoxicação aguda por triclorfon em caprinos tratados com a dose terapêutica / Acute poisoning by trichlorfon in goats given a therapeutic dose

O presente estudo descreve um surto de intoxicação por triclorfon em caprinos, que receberam pela via oral, a dosagem terapêutica do princípio ativo em questão (100mg/kg), provenientes da Universidade Estadual de Maringá, campus de Umuarama, PR. Cinquenta e três ovinos foram tratados com a mesma formulação/solução e não se observou nenhum efeito colateral nos animais referente ao tratamento com triclorfon. Das 20 cabras medicadas, cerca de 40 minutos após a administração do triclorfon, oito apresentaram os clássicos sinais clínicos de ataxia, decúbito externo-lateral, sialorreia, tremores, constrição das pupilas, dispneia com ruídos, micção e defecação involuntária, paresia espástica, timpanismo e lacrimejamento. Quase que imediatamente após a detecção destes sinais, as oito cabras foram medicadas com sulfato de atropina 1% 0,5mg/kg mais fluidoterapia. Cinco destes animais tiveram de receber nova dosagem de sulfato de atropina uma hora após a primeira aplicação, em função de alguns sinais clínicos, como tremores musculares, ainda estarem presentes. De 48 a 72 horas após a administração do triclorfon, três destes cinco animais vieram a óbito. Na necropsia, foi possível observar mucosas cianóticas, congestão de fígado, baço e rins, vasos mesentéricos congestos, vesícula biliar repleta, enfisema pulmonar, parênquima pulmonar avermelhado. Os resultados encontrados neste trabalho chamam atenção que o surto aconteceu em cabras adultas, que apresentavam boas condições clínicas e acima de tudo, receberam a dosagem terapêutica recomendada em bula pelo fabricante. Talvez isso possa indicar alguma sensibilidade mais elevada desta espécie animal à dosagem recomendada em bula do triclorfon (100mg/kg) para caprinos.

The present study describes an outbreak of trichlorfon poisoning in goats from the State University of Maringá, campus Umuarama/PR that received orally the therapeutic dose of the active ingredient in question (100mg/kg). Fifty-three sheep had been treated with the same formulation/solution and no side effects were observed in any of these sheep medicated with triclorfon. But from 20 goats medicated with trichlorfon, eight goats showed, about 40 minutes after its administration, the classic clinical signs of ataxia, external lateral decubitus, drooling, tremors, constricted pupils, noisy dyspnea, involuntary urination and defecation, spastic paresis, bloat and tearing. Almost immediately after the detection of these signals, eight goats were medicated with 1% atropine sulfate (0.5mg/kg and fluid). Five of these goats received a second dose of atropine sulfate one hour after the first application because of some clinical signs such as muscle tremor still being present. Forty-eight to 72 hours after administration of trichlorfon, three of those five goats died. At necropsy we observed cyanotic mucous membranes, congestion of liver, spleen, kidneys and mesenteric vessels, filled gallbladder, emphysema, and reddish lungs. The results of this study call attention to the outbreak that occurred in adult goats in good clinical conditions and, above all, that they received the therapeutic dosage recommended on the manufacture label. This suggests a higher sensitivity of the species to the recommended dose of trichlorfon (100mg/kg) for goats.

The effects of trichlorfon on maternal reproduction and mouse embryo development during organogenesis.

The organophosphate pesticide trichlorfon is a widely used agricultural broad spectrum insecticide. The health effects on a developing fetus of low level exposure to trichlorofon ingested by the mother in contaminated foods are unclear. We assessed reproductive and developmental toxicity in pregnant female mice following gavage-administered exposure to distilled water or to low levels (12.5, 25, or 50 mg/kg body weight/d) of trichlorofon during organogenesis (gestation days 6-15). Following sacrifice on day 17, reproductive outcomes and teratogenesis were assessed. Trichlorfon exposure did not affect maternal weight gain, organ weights, corpora lutea, implantation sites, or reproductive success, nor where external or skeletal abnormalities evident. The lack of effects of trichlorfon on any in vivo reproductive and fetuses endpoints above suggested that for trichlorfon, a hazard of reproductive toxicity below 50 mg/kg body weight/d maybe not expected. However, a well-designed epidemiological study is necessary for further risk assessment of human developing fetus exposed to trichlorfon at a lower level.

[A comparison of cholinesterase inhibitors and ginkgo extract in treatment of Alzheimer dementia]. / Ein Vergleich von Cholinesterasehemmern und Ginkgo-Extrakt in der Behandlung der Alzheimer-Demenz.

AIM: To compare the effectiveness of second-generation cholinesterase inhibitors (donepezil, rivastigmine, metrifonate) with that of the special ginkgo extract EGb 761R in Alzheimer's disease. METHOD: Analysis of the effect on cognition with the aid of the ADAS-cog.scale, placebo-adjusted, within six months; statistical evaluation of the effect using the confidence interval for the potential mean improvement. RESULTS: All medications are statistically significantly superior to placebo. The mean improvement is larger for the cholinesterase inhibitors than for the ginkgo extract. In the statistically unfavorable case, the effect of the cholinesterase inhibitors is still appreciable, but not for the ginkgo extract. CONCLUSION: Until the results of direct comparative studies are available, the present results indicate a superior effect of cholinesterase inhibitors over the ginkgo extract in the treatment of mild to moderate Alzheimer's disease.

Randomized, double-blind, placebo-controlled, multicenter study to evaluate the safety and tolerability of metrifonate in patients with probable Alzheimer disease. The Metrifonate Study Group.

A randomized, double-blind, placebo-controlled, parallel-group study was undertaken to evaluate the safety and tolerability of a once-daily oral administration of metrifonate in patients with probable mild to moderate Alzheimer disease. Metrifonate was given as a loading dose of 125-225 mg based on weight (2.5 mg/kg) for 2 weeks, followed by a maintenance dose of 50-90 mg based on weight (1.0 mg/kg) for 4 weeks. Twenty-nine patients received metrifonate, and 10 patients received placebo. Metrifonate produced a mean erythrocyte acetylcholinesterase inhibition at the end of treatment of 86.3%. The proportion of patients who experienced at least one adverse event was comparable between the metrifonate (76%) and placebo (80%) groups. Selected adverse events in disfavor of metrifonate (defined as those for which the incidence in the metrifonate and placebo groups differed by at least 10%) were diarrhea, nausea, leg cramps, and accidental injury. Adverse events were predominantly mild in intensity and transient. No severe adverse events were experienced by any patient. The most notable hemodynamic change observed during metrifonate treatment was a clinically insignificant mean decrease in the heart rate (by electrocardiogram) of approximately 9 beats/min, compared with an approximate 3-beats/min decrease for the placebo group. No muscle weakness was observed in this study. No clinically relevant laboratory abnormalities, such as liver toxicity, or changes in exercise tolerance or pulmonary function tests were found with metrifonate treatment. This metrifonate dose provided a high level of acetylcholinesterase inhibition, which was associated in these patients with a favorable safety and tolerability profile. Indeed, the magnitude of the peripheral acetylcholinesterase inhibition is the highest tolerable inhibition level yet observed.

Metrifonate enhances the ability of Alzheimer's disease patients to initiate, organize, and execute instrumental and basic activities of daily living.

The objective of this analysis was to evaluate comprehensively the efficacy of metrifonate, a long-acting acetylcholinesterase inhibitor, in improving the ability of mild-to-moderate Alzheimer's disease (AD) patients to perform activities of daily living (ADLs). Alzheimer's disease patients with Mini-Mental State Examination scores of 10 to 26 were enrolled in three 26-week trials to receive once-daily placebo (n = 430) or metrifonate 30 to 60 mg (by weight, n = 650) or 60/80 mg (by weight, n = 197). Metrifonate efficacy was assessed using the Disability Assessment for Dementia scale. Data from the three studies were pooled and analyzed retrospectively. The intent-to-treat analysis (last observation carried forward) at 26 weeks demonstrated that metrifonate significantly improved the ability of AD patients to perform ADLs when compared with placebo (30-60 mg dose, delta = 3.03; P = .002; 60/80 mg dose, delta = 5.25; P = .0002). Metrifonate significantly improved the ability of the AD patients to perform instrumental ADLs, those abilities typically lost first during the disease process (30-60 mg dose, delta = 3.88, P = .002; 60/80 mg dose, delta = 5.79, P = .003). Metrifonate also tended to improve, relative to placebo, the ability of AD patients to use three levels of executive skills when performing ADLs: initiation (30-60 mg dose, delta = 3.45, P = .001; 60/80 mg dose, delta = 5.44, P = .003), planning/organization (30-60 mg dose, delta = 4.50, P = .004; 60/80 mg dose, delta = 4.89, P = .014), and effective execution (30-60 mg dose, delta = 1.80, P = .076; 60/80 mg dose, delta = 4.06, P = .030). These results indicate that metrifonate has a beneficial effect on the ADLs in mild-to-moderate AD patients.

Metrifonate treatment of AD: influence of APOE genotype.

OBJECTIVE: To investigate whether an interaction exists between APOE genotype and the response of AD patients to metrifonate treatment and whether APOE genotype independently affects the rate of AD progression. BACKGROUND: Metrifonate is a new acetylcholinesterase inhibitor for the treatment of AD symptoms. METHODS: Data were pooled from four prospective, randomized, double-blind, placebo-controlled clinical trials and analyzed retrospectively. A total of 959 patients who received once-daily placebo (n = 374) or metrifonate (30 to 60 mg based on weight or a 50-mg fixed dose, n = 585) for up to 26 weeks agreed to APOE genotyping. RESULTS: Metrifonate clearly improved the cognitive performance of the AD patients when compared with placebo (Alzheimer's Disease Assessment Scale-Cognitive Subscale [ADAS-Cog], p = 0.0001). The interaction of APOE genotype and the metrifonate effect on cognitive performance were not significant (p = 0.25). Metrifonate also clearly improved the global function of the AD patients when compared with placebo (Clinician's Interview-Based Impression of Change with Caregiver Input [CIBIC-Plus], p = 0.0001). The interaction of APOE genotype with the metrifonate effect on global function also was not significant (p = 0.70). No significant three-way interactions were observed among APOE genotype, gender, and response to metrifonate treatment (ADAS-Cog, p = 0.68; CIBIC-Plus, p = 0.26). APOE genotype did not influence disease progression as evaluated by either cognitive performance (ADAS-Cog, p = 0.93) or global function (CIBIC-Plus, p = 0.64). CONCLUSIONS: The findings from these studies of up to 26 weeks' duration do not clearly support an interaction between APOE genotype and metrifonate treatment effects. They suggest that APOE genotypes do not necessarily predict an AD patient's response to metrifonate treatment and that APOE genotype may not influence the rate of disease progression for patients with mild to moderate AD.

Treating neurocysticercosis medically: a systematic review of randomized, controlled trials.

OBJECTIVE: To summarize the evidence from randomized controlled trials on the effects of cysticidal therapy used for treating human cysticercosis. METHODS: Published and unpublished studies in any language identified through MEDLINE (1966 - June 1999) specialized databases, abstracts, proceedings and contact with experts were analysed. Those which compared, using randomized or quasi-randomized methods, any cysticidal drug with placebo or symptomatic therapy were entered in the study. Data were extracted independently by two reviewers and trial quality assessed. Meta-analysis using fixed effects models calculated provided there was no significant heterogeneity, expressed as relative risk. RESULTS: Four trials met the inclusion criteria, treating intraparenchymatous neurocysticercosis with either albendazole or praziquantel compared to placebo or no treatment. In the two trials reporting clinical outcomes, treatment was not associated with a reduction in the risk of seizures, although numbers were small (RR 0.95, 95% CI 0.59-1.51). Four trials reported radiological outcomes, and cysticidal treatment was associated with a lower risk of cyst persistence of scans taken within six months of start of treatment (RR 0.83, 95% CI 0.70-0.99). Subsidiary analysis assuming different outcomes in patients lost to follow-up did not alter the findings of the main analysis. CONCLUSIONS: There is insufficient evidence to determine whether cysticidal therapy is of any clinical benefit to patients with neurocysticercosis. The review does not exclude the possibility that more patients remain seizure-free when treated with cysticidal drugs. Further testing through placebo-controlled trials is required.

A multicentre, randomized, double-blind, placebo-controlled study to evaluate the efficacy, tolerability and safety of two doses of metrifonate in patients with mild-to-moderate Alzheimer's disease: the MALT study.

BACKGROUND: Metrifonate is a long-lasting acetylcholinesterase inhibitor being developed for the symptomatic treatment of Alzheimer's disease (AD). OBJECTIVES: This study compared the efficacy, tolerability and safety of two doses of metrifonate in patients with mild-to-moderate AD, over a 26-week treatment period. METHODS: Six hundred and five patients were randomized to placebo (n=208), a 40/50 mg dose (40 or 50 mg by weight; n=200) or a 60/80 mg dose (60 or 80 mg by weight; n=197) metrifonate. Patients randomized to receive metrifonate were administered a once-daily loading dose of 80 or 120 mg based on weight for 2 weeks, followed by the relevant maintenance dose for 24 weeks. Four main clinical domains of AD were assessed: cognition (ADAS-cog and MMSE), psychiatric and behavioural symptoms (ADAS-noncog and NPI), instrumental and basic activities of daily living (DAD) and global functioning (CIBIC-plus, CIBIS-plus and GDS). RESULTS: ADAS-cog performance was significantly improved in the 60/80 mg and 40/50 mg dose groups, compared with placebo, in the intention-to-treat (ITT) population. In addition, statistically significant treatment differences were demonstrated between the 60/80 mg dose group and placebo on MMSE, ADAS-noncog, the NPI subitems of hallucinations and apathy, DAD, CIBIC-plus, CIBIS-plus and the GDS. The performance of the 40/50 mg dose group was also significantly superior to placebo on the CIBIS-plus and the NPI subitem aberrant motor behaviour. CONCLUSIONS: Metrifonate significantly improved a wide range of symptoms across all four clinical domains of AD in a dose-dependent manner, and was safe and well tolerated at both doses studied.

The effect of food and time of administration on the pharmacokinetic and pharmacodynamic profile of metrifonate.

OBJECTIVE: Metrifonate--via its pharmacologically active metabolite DDVP--is an inhibitor of cholinesterase effective in the treatment of Alzheimer's disease. Two separate studies were performed to investigate the influence of food and time of administration, respectively, on the concentration vs. time profiles of metrifonate and DDVP and cholinesterase inhibition. METHODS: In study I, a single dose of metrifonate 50 mg tablet was administered either in the fasting condition or within 5 min after completion of an American breakfast. In study II, a single dose of metrifonate 80 mg tablet was given either at 8:00 a.m. after overnight fasting, 7:00 p.m. (7 h after lunch) or 10:00 p.m. (4 h after dinner). Both studies were performed in a non-blind, randomized, single-centre, cross-over design in healthy Caucasian volunteers. AUC and Cmax of metrifonate and DDVP as primary parameters were compared between treatments by ANOVA and acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition vs. time profiles were assessed. RESULTS: In study I a high-fat/high-calorie breakfast had no effect on the AUC of DDVP, while its Cmax was decreased to 56% and tmax was prolonged, compared to the fasting condition. The effects on metrifonate were similar. In study II bioequivalence was shown for AUC and Cmax of DDVP when comparing administration of metrifonate at 8:00 a.m. and 7:00 p.m. Administration at 10:00 p.m. also had no effect on AUC of DDVP while a reduction in rate of absorption was observed. In both studies the equivalence in AUC of DDVP was paralleled by equivalent effects on BChE inhibition. Following single metrifonate administration little inhibition of AChE was observed. Metrifonate was well tolerated. CONCLUSIONS: Delayed gastric emptying is likely to cause the reduced rate of absorption of metrifonate with food. In view of unchanged bioavailability of its active metabolite, this food effect is considered to be without clinical relevance and metrifonate can be administered with or without food. The decrease in rate of absorption following administration of the drug at 10:00 p.m. is either a protracted food effect or an effect of time. As the bioavailability of DDVP as well as pharmacodynamic profiles were independent of the time of administration it is concluded that metrifonate can be taken in the morning or evening without compromising its safety or efficacy.

Pharmacokinetics and pharmacodynamics of the acetylcholinesterase inhibitor metrifonate in patients with renal impairment.

The aim of this study was to assess the influence of renal function on the pharmacokinetics, pharmacodynamics, safety, and tolerability of the acetylcholinesterase inhibitor metrifonate. Four groups of six age- and gender-matched subjects with varying degrees of renal function (creatinine clearances more than 90, 60-90, 30-60, and less than 30 mL/min/ 1.73 m2, respectively) were administered a single 50-mg oral dose of metrifonate. Blood and urine samples were collected for 24 hours and concentrations of metrifonate and its metabolites dichlorvos, dichloroacetic acid, and M3 were determined. Inhibition of acetylcholinesterase activity in erythrocytes and butyrylcholinesterase in plasma were also measured. Metrifonate was well tolerated in all treatment groups. The urinary excretion of metrifonate and dichlorvos decreased with decreasing renal function but accounted for less than 2% of the elimination. There were no statistically significant differences in primary pharmacokinetic parameters--Cmax, t(max), area under the concentration-time curve (AUC), and t1/2--of metrifonate and dichlorvos among the different groups. The excretion of dichloroacetic acid and M3 was not influenced by renal impairment. Acetylcholinesterase was not inhibited, whereas butyrylcholinesterase was inhibited markedly but independently of renal function. No metrifonate dose adjustments are needed when treating subjects with renal impairment.

The effects of metrifonate on the cognitive, behavioral, and functional performance of Alzheimer's disease patients. Metrifonate Study Group.

BACKGROUND: The objective of this study was to evaluate the efficacy and safety of metrifonate, a long-acting acetylcholinesterase inhibitor, in patients clinically diagnosed with probable Alzheimer's disease of mild-to-moderate severity. METHOD: This was a prospective, multicenter, 26-week, double-blind, parallel group study. The 264 randomized patients met diagnostic criteria of the National Institute of Neurological and Communicative Diseases and Stroke and the Alzheimer's Disease and Related Disorders Association for probable Alzheimer's disease. Patients had Mini-Mental State Examination (MMSE) scores of 10-26 and ischemic scores (Rosen modification) of <4. Metrifonate-treated patients received a single 50-mg dose once daily. The efficacy of metrifonate was investigated with respect to 3 symptom domains. Cognitive performance was analyzed using the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) and the MMSE. Psychiatric and behavioral disturbances were analyzed using the Neuropsychiatric Inventory (NPI) and the ADAS-Noncognitive subscale (ADAS-Noncog). The ability to perform instrumental and basic activities of daily living was evaluated using the Disability Assessment for Dementia (DAD) scale. Additionally, global state was assessed using the Clinician Interview-Based Impression of Change with Caregiver Input (CIBIC-Plus) scale. RESULTS: After 26 weeks of metrifonate therapy, a statistically significant benefit of metrifonate was observed in the cognitive performance of Alzheimer's disease patients (ADAS-Cog, t = 2.55, df = 237, p = .012; MMSE, t = 4.60, df = 237, p = .0001). Metrifonate also significantly attenuated the deterioration in activities of daily living of the patients (DAD total score, t = -2.11, df = 233, p = .036) and relieved patients' psychiatric and behavioral disturbances (NPI total score, t = 2.51, df = 233, p = .013). In addition, metrifonate significantly improved the scores for the global state of the patients (CIBIC-Plus, t = 2.07, df = 232, p = .039). Metrifonate was well tolerated; adverse events were predominantly mild in intensity, and no hepatotoxicity was observed. CONCLUSION: In this study, metrifonate was safe and well tolerated. It benefited the cognitive decline, psychiatric and behavioral disturbances, impaired ability to perform instrumental and basic activities of daily living, and global state of patients diagnosed with mild-to-moderate Alzheimer's disease.

Efficacy and safety of a loading-dose regimen versus a no-loading-dose regimen of metrifonate in the symptomatic treatment of Alzheimer's disease: a randomized, double-masked, placebo-controlled trial. Metrifonate Study Group.

This prospective, randomized, double-masked, placebo-controlled, parallel-group study assessed the safety and efficacy of 2 dosage regimens of once-daily metrifonate in patients with probable Alzheimer's disease (AD) of mild-to-moderate severity. A total of 395 patients were randomized to receive placebo (n = 134) or metrifonate in 1 of 2 regimens. The loading-dose group (n = 133) received a daily loading dose of metrifonate 100 mg or 150 mg (by weight) for 2 weeks, followed by a daily maintenance dose of metrifonate 50 mg for 4 weeks; the no-loading-dose group (n = 128) received the daily maintenance dose of metrifonate 50 mg for 6 weeks. The primary measure of efficacy was the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog); secondary measures of efficacy included the Mini-Mental State Examination (MMSE), the Clinician's Interview Based Impression of Change with Caregiver Input (CIBIC-Plus), the Clinician's Interview Based Impression of Severity with Caregiver Input (CIBIS-Plus), and the ADAS-Noncognitive Subscale (ADAS-Noncog). Safety was assessed by the prevalence of premature study termination and treatment-emergent adverse events, as well as by changes in vital signs, findings on electrocardiographic and neurologic examinations, and abnormalities on laboratory tests. At 4 weeks of treatment, defined by the protocol as the target efficacy determination, the mean ADAS-Cog scores of the intent-to-treat population (last observation carried forward) favored the loading-dose group versus the placebo group, but the difference was not statistically significant. However, at week 6, the difference in mean ADAS-Cog scores was statistically significant compared with placebo. At neither week 4 nor week 6 was there a statistically significant difference in the mean ADAS-Cog scores of the no-loading-dose and placebo groups. For the CIBIC-Plus, the treatment difference between the placebo and loading-dose groups significantly favored metrifonate at week 6 but not at week 4, whereas the treatment difference between the placebo and no-loading-dose groups was statistically significant at both time points. For the MMSE, CIBIS-Plus, and ADAS-Noncog, treatment differences for both groups versus placebo did not reach statistical significance at either week 4 or 6. Assessment of the frequency of adverse events in metrifonate-treated patients revealed that the no-loading-dose regimen was better tolerated than the loading-dose regimen. Given the overall similar efficacy and more favorable safety profile associated with the no-loading-dose regimen versus the loading-dose regimen observed in this study, the no-loading-dose regimen appears to be the better strategy for initiating metrifonate treatment in patients with probable AD of mild-to-moderate severity.

Metrifonate: a new agent for the treatment of Alzheimer's disease.

The pharmacology, pharmacokinetics, clinical efficacy, and adverse effects of metrifonate, a long-acting cholinesterase inhibitor, are discussed. Attempts to correct the central cholinergic deficits associated with Alzheimer's disease have included administration of cholinergic precursors, cholinergic agonists, and cholinesterase inhibitors. To date, two reversible cholinesterase inhibitors-tacrine and donepezil-have been marketed. Metrifonate, an organophosphate, is converted nonenzymatically to 2,2-dichlorovinyl dimethyl phosphate (DDVP), the active enzyme inhibitor. DDVP produces irreversible inhibition of brain cholinesterase that lasts for several days; enzyme recovery is dependent on synthesis of new enzyme. Several preclinical studies have demonstrated cognition-enhancing effects of metrifonate in animals. Trials in humans have shown improvement on the Alzheimer's Disease Assessment Scale, in Mini-Mental State Examination scores, and in the Clinician's Interview-Based Impression of Change with caregiver input. Clinical improvement noted with metrifonate appears similar to that seen with other cholinesterase inhibitors. Adverse effects noted in clinical trials have been associated primarily with the gastrointestinal tract and have been mild. Metrifonate appears to be a promising agent for the treatment of the symptoms of Alzheimer's disease.

Seizures in patients receiving concomitant antimuscarinics and acetylcholinesterase inhibitor.

Seizures occurred in two patients with probable Alzheimer's disease who were receiving long-term treatment with metrifonate, an irreversible acetylcholinesterase inhibitor. In both patients seizures were associated with discontinuation of short-term agents with high antimuscarinic properties. Hence, abrupt discontinuation of antimuscarinics or anticholinergics with high antimuscarinic properties in patients receiving long-term acetylcholinesterase inhibition therapy may be associated with a reduction of seizure threshold. With increasing administration of acetylcholinesterase inhibitors for patients with Alzheimer's disease, practitioners should be aware of the potential for drug-drug interactions and other complications. In general, it is good medical practice to avoid concomitant administration with centrally acting anticholinergic agents.

The clinical trial protocol of the Metrifonate in Alzheimer's Trial (MALT).

The promising results of early trials in Alzheimer's disease with the acetylcholinesterase inhibitor metrifonate prompted initiation of the Metrifonate in ALzheimer's Trial (MALT). MALT is an international, randomized, double-blind, placebo-controlled, parallel-group study which was designed to determine, over a 26-week period, the efficacy, tolerability and safety of two doses of metrifonate in patients with probable Alzheimer's disease. A total of 605 patients were randomized to receive either a daily dose of oral metrifonate 40/50 mg (n = 200, by body weight <65 kg/> or =65 kg) or metrifonate 60/80 mg (n = 197, by body weight <65 kg/> or = 65 kg). Patients were assessed in the key symptom domains of Alzheimer's disease, i.e. cognition, behavioural and psychiatric disturbances, activities of daily living and global function. In summary, administration of metrifonate for 26 weeks to the intent-to-treat population significantly benefited cognitive performance, global function and certain aspects of behaviour and functional ability compared with placebo. These efficacy results were associated with high levels of acetylcholinesterase inhibition and a good safety and tolerability profile. The protocol of MALT is discussed here. Full results of the study will be available in a separate publication.

The pharmacological basis for metrifonate's favourable tolerability in the treatment of Alzheimer's disease.

Metrifonate, through its pharmacologically active metabolite 2,2-dichlorovinyl dimethylphosphate (DDVP), is a long-acting cholinesterase inhibitor for the symptomatic treatment of mild-to-moderate Alzheimer's disease. Clinical studies with Alzheimer patients have demonstrated the favourable safety and tolerability profile of this drug. Metrifonate, at therapeutic doses for Alzheimer's disease, achieves high levels of cholinesterase inhibition, i.e. > or =70%, without the need for dose escalation. This is a consequence of the low rate of fluctuation of enzyme activity during therapy with metrifonate. This, in turn, is due to the protracted hydrolytic transformation of metrifonate into DDVP, the resulting smooth onset of cholinesterase inhibition, and the subsequent long duration of action which far outlasts the presence of the active drug in the body. Both metrifonate and DDVP are rapidly metabolized and eliminated from the body. Further, their metabolism does not involve the cytochrome P450 system and both compounds show low plasma protein binding. These pharmacokinetic features account, at least in part, for the favourable safety and tolerability profile of metrifonate as they suggest a minimal risk of drug-drug interactions with other likely co-medications in the long-term therapy of Alzheimer patients.

Metrifonate benefits cognitive, behavioral, and global function in patients with Alzheimer's disease.

OBJECTIVE: To evaluate the efficacy and safety of metrifonate, an acetylcholinesterase inhibitor, in patients clinically diagnosed with probable Alzheimer's disease (AD) of mild to moderate severity. METHODS: A prospective, 36-week, multicenter, double-blind, randomized, parallel group study of metrifonate in probable AD patients, including a 2-week screening period, a 26-week double-blind treatment period, and a follow-up visit at 8 weeks post-treatment. A total of 24 ambulatory clinics in the United States in a variety of settings, including contract research organizations, public health facilities, and universities. Patients met diagnostic criteria for probable AD as defined by the work group of the National Institute for Neurological and Communicative Diseases and Stroke and the Alzheimer's Disease and Related Disorders Association. Patients had Mini-Mental State Examination (MMSE) scores of 10 to 26 and Ischemic Scores (Rosen Modification) of <4. A total of 408 patients were enrolled. Percentages of patients completing double-blind treatment were 88% and 79% in the placebo and metrifonate groups, respectively. Rates of discontinuation due to adverse events were 4% in the placebo group and 12% in the metrifonate group. Placebo or metrifonate was administered once daily. Metrifonate-treated patients received a loading dose of 100 to 180 mg based on weight (2.0 mg/kg) for 2 weeks, followed by a maintenance dose of 30 to 60 mg based on weight (0.65 mg/kg) for 24 weeks. Primary efficacy variables were the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) and the Clinician's Interview-Based Impression of Change with Caregiver Input (CIBIC-plus). Secondary efficacy variables included the Neuropsychiatric Inventory (NPI), the Disability Assessment in Dementia, the Global Deterioration Scale (GDS), the ADAS-Noncognitive subscale (ADAS-Noncog), the MMSE, and the Clinician's Interview-Based Impression of Severity with Caregiver Input (CIBIS-plus). Outcome measures reflected changes from baseline at week 26 for all variables. Safety was assessed with incidences of premature termination, treatment-emergent events and mortality, and routine safety evaluations. RESULTS: After 26 weeks of metrifonate therapy, a 2.86-point treatment difference (p = 0.0001) was observed in the ADAS-Cog scores of the intent-to-treat AD patients. The treatment difference in the mean CIBIC-plus score at this time was 0.28 points (p = 0.0071). At week 26, treatment differences also were observed in the mean NPI total score (p = 0.0161). Analysis of the remaining secondary efficacy variables showed treatment differences that favored metrifonate but did not reach statistical significance. Metrifonate adverse events were predominantly mild in intensity. No hepatotoxicity was observed. CONCLUSIONS: Metrifonate was safe and well-tolerated. It enhanced not only the cognitive and global function, but also the behavioral function of patients diagnosed with mild to moderate AD. Therefore, metrifonate appears to be useful in the symptomatic treatment of AD.