Metrifonate. Summary of toxicological and pharmacological information available.

The organophosphorus compound 0,0-dimethyl-(1-hydroxy-2,2,2-trichloroethyl)-phosphonate was introduced as an insecticide, trichlorfon, in 1952 (Lorenz et al., 1955) and as a drug, metrifonate, in the treatment of schistosomiasis in 1960 (Lebrun and Cerf, 1960). This organophosphorus compound is unique in that it has been claimed not to be a direct acting cholinesterase inhibitor but being transformed nonenzymatically into an active component dichlorvos, 2, 2-dichlorovinyl dimethyl phosphate (DDVP). The evidence for this transformation has mostly been indirect. Recently it has been proved chemically and quantitatively that this transformation occurs in the animal body (Nordgren et al., 1978). Metrifonate is the sole organophosphorus compound currently studied clinically in schistosomiasis. A substantial therapeutic effect is obtained only in Schistosoma haematobium infections. In this review on available data of metrifonate it is suggested that further more detailed studies of both S. haematobium and S. mansoni are necessary. This should include studies of the enzymic properties of the worms and the reaction of their esterases towards both metrifonate and DDVP as well as the pharmacokinetics of these compounds in man. In addition there are still unsolved discrepancies reported regarding organ toxicity of the compound which may, however, be due to different grades of parity of the test material.

Transformation and action of metrifonate.

Chemical formation of dichlorvos (2, 2-dichlorovinyl dimethyl phosphate) was found to occur in mouse brain after i.p. injection of metrifonate (2, 2, 2-trichloro-1-hydroxyethyl dimethyl phosphonate). A mass fragmentographic technique was used. Different isotopic variants were used both as internal standards and to compensate for dichlorvos formed during the workup procedure. The dichlorvos formed in vivo was found to have its maximal concentration a few minutes after the maximum of the metrifonate itself. The effect of metrifonate and dichlorvos on acetylcholine levels, acetylcholinesterase activity and synthesis rate of acetylcholine in mouse brain was also studied. In all three cases the effect of metrifonate was found to be prolonged and delayed as compared to the effect of dichlorvos. It is concluded that metrifonate acts as a slow release formulation in the body giving rise to dichlorvos nonenzymatically. This circumstance at least partly explains its efficacy in the treatment of schistosomiasis.

Biotransformation of amitriptyline in man: interaction with phenothiazines.

The biotransformation modification of amitriptyline by phenothiazines has been studied in 65 depressive inpatients. Thirty-four of them were treated with oral amitriptyline and 31 with a combination of amitriptyline and phenothiazine. Urinary and plasmatic results showed a decrease in hydroxylated metabolites of amitriptyline (OHAMTc and OHAMT) in patients with added phenothiazine.

Cardiac beta-adrenergic sensitivity in depression: relation with endogenous subtype and desipramine response.

The authors studied the responsiveness of cardiac beta-receptors to isoproterenol, a noradrenergic agonist, in 29 depressed patients and 13 control subjects. They showed a significantly lower sensitivity in depressed patients as compared with the control subjects. Focussing on the group of depressed patients without antidepressant treatment in the month preceding the study (n = 15) in order to avoid a bias, the following significant results were obtained: cardiac beta-adrenergic receptor sensitivity was lower in patients suffering from endogenous depression than in those suffering from reactive depression (as classified by Newcastle Scale). There was a negative linear relation between cardiac beta-adrenergic sensitivity and the posttreatment clinical state (as expressed by the MADRS score) for the 9 patients who ended a 3-week desipramine treatment period.

Biotransformation of amitriptyline in alcoholic depressive patients.

The biotransformation of amitriptyline (AMT) during steady state conditions was studied in plasma and urine from 11 nonalcoholic and 10 alcoholic depressive inpatients treated with oral AMT. The 2 groups of patients had a different pattern of biotransformation. The Demethylation of AMT was lower in alcoholic than in nonalcoholic depressive patients, and conjugation and hydroxylation of AMT were also more marked in the former group. The results may be of clinical relevance since the conjugates of AMT are inactive.

Biological markers in depression. Monoamine metabolites in urine of depressed patients and normal subjects.

Urinary elimination of HVA, MHPG and 5-HIAA was studied in 22 depressed inpatients before and after 28 days of antidepressant treatment. Mean values did not change significantly during treatment, and were not related significantly to recovery in patients. Some marked changes in urinary metabolite levels were, however, observed in individual patients, and could be related to changes in their depression. The direction of change in urinary monoamine metabolites during treatment was associated with pretreatment levels, in that high pretreatment values tended to decrease whereas low pretreatment levels tended to increase.

Flagellin from Listeria monocytogenes is glycosylated with beta-O-linked N-acetylglucosamine.

Glycan staining of purified flagellin from Listeria monocytogenes serotypes 1/2a, 1/2b, 1/2c, and 4b suggested that the flagellin protein from this organism is glycosylated. Mass spectrometry analysis demonstrated that the flagellin protein of L. monocytogenes is posttranslationally modified with O-linked N-acetylglucosamine (GlcNAc) at up to six sites/monomer. The sites of glycosylation are all located in the central, surface-exposed region of the protein monomer. Immunoblotting with a monoclonal antibody specific for beta-O-linked GlcNAc confirmed that the linkage was in the beta configuration, this residue being a posttranslational modification commonly observed in eukaryote nuclear and cytoplasmic proteins.

Clinical response and plasma concentration of amitriptyline and its metabolite nortriptyline.

Plasma levels of amitriptyline and nortriptyline were measured twice weekly in 62 patients treated for three weeks with i.m. amitriptyline 120 mg/day. In half the patients the ratio of amitriptyline to nortriptyline was under 1 and in the other half it was greater than 1. 30 of these 62 patients were clinically monitored with the Hamilton Rating Scale and the side effects of the drug were recorded. There was no correlation between plasma level of the drug and its side effects, but there was a statistically significant curvilinear correlation between the plasma levels of amitriptyline plus nortriptyline and nortriptyline alone, and the clinical effect. The practical value of this type of investigation was demonstrated by showing that patients whose drug plasma level was not in the therapeutic range, were clinically improved after adjustment of the dose. The plasma level of amitriptyline plus nortriptyline must lie between 60 to 220 ng/ml, and that of nortriptyline between 60 to 140 ng/ml, to obtain the best clinical effect. Associated treatments, age, weight and sex of patients, and the type of depression did not appear significantly to affect the plasma level of the drug.

Culture-independent phylogenetic analysis of the faecal flora of the rat.

The dominant faecal flora of the rat was determined using randomly cloned 16S rDNA comparative sequence analysis. A total of 109 near full-length 16S rDNA clones were sequenced, representing 69 unique 16S rRNA phylotypes or operational taxonomic units (OTUs). Estimates of species richness indicated that approximately 338 species were present in the faeces, suggesting that only 20% of species were identified. Only two of 39 Gram-negative clones aligned with previously cultured species, the remainder fell into a separate lineage within the Bacteroides-Cytophaga phylum. Several clones within this new group were related to 16S rDNA sequences previously identified from mouse faeces. Lactobacilli were the most abundant Gram-positive species, representing 23% of the total clones but only 7% of OTUs. The remaining Gram-positive clones were distributed among the Clostridium coccoides group (9%), the Clostridium leptum subgroup (18%), and throughout the low GC Gram-positive bacteria (13%). The majority of OTUs (63/69 or 91%) were less than 97% homologous to previously cultured bacteria. Faecal samples were also cultured using a variety of anaerobic media. With the exception of the lactobacilli, the cultured isolates demonstrated low species diversity and poorly reflected the population, as defined through comparative sequence analysis.

Biotransformation of amitriptyline in depressive patients: urinary excretion of seven metabolites.

The urinary excretion of amitriptyline (AMT) and seven of its metabolites was studied by mass spectrometry in 10 depressive in-patients treated to steady-state condition with oral amitriptyline. An average of 68.3% of the dose was recovered in the urine, of which 68.6% was present as conjugates. Hydroxynortriptyline and its conjugate represented 54% of the total recovery. There was marked variation in metabolite pattern between patients. The variations were not due to concomitant medication with benzodiazepines. There was no correlation between the plasma and urine concentrations of AMT and its metabolites, except for amitriptyline conjugates. Two groups of patients could be distinguished - low and high excretors, who displayed alternative routes of metabolism. The disappearance rate of AMT from plasma was determined by the metabolic clearance of AMT to its metabolites. It varied considerably between patients.

Quality control of amitriptyline and nortriptyline plasma level assessments: a multicenter study.

Numerous studies report about the relationship between the clinical effectiveness of amitriptyline (At) and the plasma level of this drug and of its most important metabolite, nortriptyline (Nt). These agents are therefore very frequently examined for clinical applications and for research programmes in specialized laboratories. The experience with antiepileptic drugs suggests the necessity of quality controls for antidepressants also. Therefore, five institutions in Western Europe performed two such experiments within a year. Two kinds of blood samples were sent for analysis: 1. plasma samples spiked with different quantities of At and Nt from an untreated subject; 2. plasma samples from patients treated with clinical doses of At. Each laboratory happened to use a different analytical method: TLC, HPLC, GC-NPD, GC-FID and GC-MS. The results clearly show the usefulness and the necessity of quality controls for this category of drugs as well. They form the basis for the improvement of the methods of each laboratory in particular. In this context, intralaboratory quality controls are also possible, if one disposes of two different methods. The findings of this study suggest that published reports on relationships between clinical and pharmacological parameters should be considered critically as to possible methodological bias.

Metabolism of amitriptyline in patients with chronic renal failure.

The metabolism of amitriptyline (AMT) has been studied in two groups of depressed in-patients on long term AMT therapy: 11 patients with no other major disease and 8 patients with chronic renal failure, who were being dialysed. The patients with renal insufficiency had decreased concentrations of AMT, nortriptyline (NT) and their unconjugated hydroxymetabolites compared to patients with normal kidney function. The plasma levels of conjugated products were extremely high in the uraemics. The latter metabolites are probably inert. The reduced concentration of unconjugated hydroxymetabolites , which are active compounds, may decrease the clinical effectiveness of the drug.

Minor and clinically non-significant interaction between toloxatone and amitriptyline.

The possibility of a pharmacokinetic interaction between amitriptyline and toloxatone (a new MAOI-A) has been studied in 17 depressed in-patients. Amitriptyline and its demethylated and hydroxylated metabolites in blood and urine were measured at steady state after the administration of amitriptyline with and without toloxatone in steady state. The metabolic status of patients was determined using the dextromethorphan phenotyping test. There was only a minor pharmacokinetic interaction between amitriptyline (AMT) and toloxatone, with a small increase in the AMT/NT (nortriptyline) plasma ratio: 0.68 before and 0.78 after toloxatone. The urinary excretion and plasma levels of AMT and its metabolites were not affected by the co-therapy. Three of the patients were poor metabolisers, but this did not predict the magnitude of the drug interaction. The interaction does not justify plasma level monitoring of amitriptyline as the change in pharmacokinetics was so small.

Effect of repeated injection and continuous infusion of omeprazole and ranitidine on intragastric pH over 72 hours.

OBJECTIVE: In healthy subjects and patients with bleeding peptic ulcers, ranitidine and omeprazole, given parenterally, achieve high intragastric pH values on the first day of therapy. However, data on the antisecretory effect beyond the first 24 h is scanty. In addition, the superiority of either infusion or injection of omeprazole remains unproven. Thus, we have compared the antisecretory effect of high dose omeprazole and ranitidine infusion and injection over the critical first 72 h. METHODS: A total of 34 healthy volunteers were randomized into a double-blind crossover 72 h intragastric pH-metry study (data compared: median pH, percentage of time with pH >4 and pH >6). Omeprazole-infusion: initial bolus of 80 mg + 8 mg/h; omeprazole-injection: initial bolus of 80 mg + 40 mg/6 h; Ranitidine-infusion: initial bolus of 50 mg + 0.25 mg/kg/h; ranitidine-injection: 100 mg/6 h. RESULTS: Omeprazole-infusion versus ranitidine-infusion: on day 1: median pH 6.1 vs 5.1 (p = 0.01) and 95% vs 70% was pH >4 (p < 0.01); on day 2: median pH 6.2 vs 3.2 (p < 0.01); and 100% vs 38% was pH >4 (p < 0.01); on day 3: median pH 6.3 vs 2.7 (p < 0.01); 100% vs 26% was pH >4 (p < 0.01). Injections of both drugs were significantly less effective than the infusions on day 1. Thereafter, omeprazole injection was almost as effective as omeprazole infusion, whereas ranitidine injection and infusion were equally effective. CONCLUSION: Our study shows, for the first time, that omeprazole infusion was significantly superior to all other regimens by having a high median pH >6 on each day. The tolerance effect of ranitidine, however, led to a rapid loss of antisecretory activity on days 2 and 3, rendering it inappropriate for situations in which high intragastric pH-levels appear to be essential.

Estudo clínico e biológico em deprimidos tratados com amineptina / Clinical and biological study in depressed women inpatients treated by amineptine

A resposta do GH, TSH e da PRL ao TRH foi estudada em 10 pacientes mulheres hospitalizadas antes e depois de 21 dias de tratamento pela amineptina. A eliminação urinária do MHPG (total, glucuronídeo, sulfato), 5 HIAA e HVA também foram estudados um dia antes dos dois testes TEH e após 5 dias de um regime pobre em tiramina. Nenhuma conclusão foi possível a partir do GH, TSH, PRL, HVA e 5 HIAA. O MHPG total foi diminuído significativamente com o tratamento, devido à redução da fração glucuronídeo. Esta ação no metabolismo da noradrenalina tem uma origem periférica. Nenhuma correlação foi possível entre o MHPG e outros resultados clínicos e biológicos. A redução do glucuronídeo não foi verificada em nove mulheres deprimidas tratadas com desimipramina durante 21 dias. A redução do MHPG glucuronídeo parece resultar da ação da amineptina