Comparative uptake and translocation of pharmaceutical and personal care products (PPCPs) by common vegetables

Reuse of treated wastewater to irrigate agricultural crops is increasing in many arid and semi-arid areas around the world. The presence of numerous pharmaceutical and personal care products (PPCPs) in treated wastewater and their potential transfer into food produce such as vegetables poses an unknown human health risk. The goal of this study was to identify PPCPs that have a comparatively high potential for plant uptake and translocation. A total of 20 frequently-occurring PPCPs were compared for their accumulation into four staple vegetables (lettuce, spinach, cucumber, and pepper) grown in nutrient solutions containing PPCPs at 0.5 or 5μgL(-1). Triclocarban, fluoxetine, triclosan, and diazepam were found at high levels in roots, while meprobamate, primidone, carbamazepine, dilantin, and diuron exhibited more active translocation from roots to leaves. Root uptake of neutral PPCPs was positively correlated with the pH adjusted log Kow(i.e., log Dow), and was likely driven by chemical adsorption onto the root surfaces. In contrast, translocation from roots to leaves was negatively related to log Dow, suggesting hydrophilicity-regulated transport via xylems. Compounds preferentially sorbed to roots should be further evaluated for their uptake in tuber vegetables (e.g., carrot, radish) under field conditions, while those easily translocated into leaves (e.g., carbamazepine, dilantin) merit focused consideration for leafy and other vegetables (e.g., lettuce, cucumber). However, estimation of dietary intake by humans suggested the implied risks from exposure to PPCPs via wastewater irrigation to be negligible.

Transfer of Carisoprodol to Breast Milk

There is no published information on the transfer of the centrally acting muscle relaxant carisoprodol and its active metabolite meprobamate into breast milk. The objective of this study was to quantify the excretion of carisoprodol and meprobamate in human milk and estimate the dose received by breast-fed infants. The concentrations of carisoprodol and meprobamate were measured in breast milk on 4 consecutive days at steady-state conditions in one woman using carisoprodol 2100 mg/d. The average milk concentrations were 0.9 microg/mL for carisoprodol and 11.6 microg/mL for meprobamate. Based on the milk concentrations measured, the absolute dose ingested by an exclusively breast-fed infant could be estimated at 1.9 mg/kg per day, and the relative dose would be 4.1% of the weight-adjusted maternal dose. No adverse effects were observed in the infant, but the infant was partly fed with formula because of insufficient maternal milk production. Thus, the authors consider that at least during prolonged use, lactation is generally inadvisable until more clinical data are available.

Formation of meprobamate from carisoprodol is catalysed by CYP2C19

Carisoprodol is a muscle relaxant analgesic, which has an active metabolite i.e. meprobamate. We conducted an open three-panel single-dose administration study with 15 healthy volunteers: five poor metabolizers of mephenytoin, five poor metabolizers of debrisoquine and five extensive metabolizers of both substrates. The aim was to investigate if the elimination of carisoprodol and meprobamate is dependent on the two metabolic polymorphisms of mephenytoin and debrisoquine. The subjects were given single oral doses of 700 mg carisoprodol and 400 mg meprobamate on separate occasions. The disposition of carisoprodol was clearly correlated to the mephenytoin hydroxylation phenotype. The mean serum clearance of carisoprodol was four times lower in poor metabolizers of mephenytoin than in extensive metabolizers, which confirms the hypothesis from our previous study that N-dealkylation of carisoprodol cosegregates with the mephenytoin hydroxylation polymorphism. However, mean serum clearance of meprobamate did not differ between the two groups. Also, polymorphic debrisoquine hydroxylation did not influence the elimination of carisoprodol or meprobamate. Poor metabolizers of mephenytoin thus have a lower capacity to metabolize carisoprodol and may therefore have an increased risk of developing concentration dependent side-effects such as drowsiness and hypotension, if treated with ordinary doses of carisoprodol.

Pharmacological studies on meprobamate incorporation in human beard hair

The time course of appearance of meprobamate in beard hair after single oral administration (400, 800, or 1200 mg) was monitored in 3 groups of 4 subjects by GC/MS. Meprobamate appeared in beard hair approximately 4-5 days after administration and peaked during the 7-9th day. Drug levels in beard hair appeared to be dose-related.

Continuous arteriovenous hemoperfusion in meprobamate poisoning

A patient with severe meprobamate poisoning presented within 4 h after suicidal ingestion of an unknown amount of the drug. The patient was unconscious, unresponsive, and hypotensive. Continuous arteriovenous hemoperfusion with coated activated charcoal resulted in a clearance of 198.8 +/- 15.6 mL/min with an extraction ratio of 0.66 +/- 0.05 (n = 3). There was almost complete elimination of the drug from the blood by 16 h. Continuous arteriovenous hemoperfusion, which can be performed in areas where dialysis facilities are not available, may be an effective adjunct to the treatment of acute meprobamate intoxication, particularly in patients with profound hypotension.

[The effect of phytin, benzonal and their combination administered prophylactically on the pharmacodynamics of drugs metabolized in the liver in hypokinesia]

Hexenal, meprobamate, amidopyrine and ethylmorphine produced a significantly marked effect in animals under hypokinesia as compared with normal rats. When phytin, benzonal and their combination were used for preventive purposes, impaired pharmacodynamics of the tested drugs metabolizing in the liver disappeared. The investigations demonstrated that the preventive use of phytin in combination with benzonal is the most optimal in correcting the impairments of drug pharmacodynamics in hypokinesia.

Effect of long-term ethanol administration on meprobamate level in brain of rat

Effect of long-term ethanol administration on brain meprobamate concentration (BrMC) was investigated using rats. In ethanol-non-pretreated rats, the average ratio of the maximum BrMC (BrMCmax) to the maximum blood meprobamate concentration (BMCmax) was 0.75 when 25 mg/kg meprobamate were intraperitoneally administered to rats singly or together with ethanol (2 g/kg or 4 g/kg). By a pretreatment of the animals with ethanol at the daily dose of 0.4 g or 0.6 g for 25 days, the average ratio of BrMCmax to BMCmax was 0.91 when the same dose of meprobamate were given into the abdominal cavity. It was considered that by long-term ethanol administration the permeability of blood-brain barrier to meprobamate might be accelerated, resulting in an increase in BrMC.

Biological valuation of extra-corporeal techniques in acute poisoning

The efficiency of dialysis methods a/o hemoperfusion in acute poisoning cannot be clinically estimated, because: a) Concomitant intestinal absorption, hepatic metabolism and urinary excretion must be taken into account. b) With supportive treatment alone, spontaneous recovery usually occurs in 98% of the intoxications in Intensive Care Units. The efficiency of these methods can only be estimated biologically. Measuring the blood level at the beginning and the end of the treatment as well as measuring the clearances of the drug is misleading. A better method is to measure the amount of extracted drug, either indirectly by calculation (from hourly differences of arteriovenous measures of drug concentration multiplied by the blood flow) or directly by elution of the cartridge or measures in dialysis fluid. Plasma kinetics under dialysis a/o hemoperfusion should be compared with spontaneous toxicokinetic of the substance and not with pharmacokinetic data. The experience of toxicologists has shown dialysis a/o hemoperfusion to be ineffective for drugs with weak extra-cellular distribution (such as Digoxine, Tricyclic drugs, heavy Metals, Colchicine). In the case of intoxication with Paraquat or Paracetamol, there is a negative correlation between the amount of removed intoxicant and the survival: death is likely to occur when the procedure has been very productive. In the case of intoxication by hypnotic drugs, one hemodialysis a/o hemoperfusion allows the removal of an average of 4-12% of the ingested barbiturates, 7-17% of the ingested Meprobamate. Whether these results can be judged satisfactory, life-saving of insignificant is largely a matter of personal standards.

[Characteristics of drug pharmacodynamics in irradiated rats]

A whole-body exposure of rats to 8 Gy radiation is ineffective in 3 days, and in 6 days, it prolongs considerably the effect and increases the pharmacological activity of hexenal, meprobamate, ethylmorphine, and amidopyrine, inhibits the activity of amidopyrine demethylase, aniline hydroxylase, NADPH-cytochrome c reductase, and reduces the content of protein, cytochromes P-450 and b5 in a microsomal liver fraction.

Interactive effects of acute ethanol administration on meprobamate levels in blood and brain of rabbit and rat

In the simultaneous administration of meprobamate and ethanol to rabbits, the blood meprobamate concentration (BMC) increased greatly when the maximum blood ethanol concentration (BECmax) exceeded 1.0 mg/ml. Thus, we subjected the rabbits to continuous infusion of ethanol so as to make the blood ethanol concentration (BEC) constant and administered meprobamate by intravenous injection. Elimination of meprobamate became slow at about the BEC of 0.5 mg/ml and the degree reached almost maximum around the BEC of 1.0 mg/ml. The elimination rate did not change any more even when the BEC was raised higher. In the study conducted to elucidate the relationship between the BMC and brain meprobamate concentration (BrMC) using rats, it was found that meprobamate would show similar movements and its level would rise extremely by an acute administration of ethanol. It was indicated that the effect of ethanol on reinforcement of meprobamate activity would appear strongly by potentiation effect.

Meprobamate kinetics during and after terminated hemoperfusion in acute intoxications

We report four cases of severe meprobamate intoxication. Maximal plasma levels reached 800 (176), 816 (180), 863 (190) and 923 mumol/l (203 mg/l). All patients survived without sequelae including one patient resuscitated from cardiac arrest. The clinical course was complicated by coma, hypotension, and hypothermia in all patients. Three cases were treated with charcoal hemoperfusion with mean hemoperfusion clearance ranging from 134-164 ml/min compared to 174 ml/min in one case treated with resin filter and the same blood flow of 200 ml/min. In two cases, a mean renal meprobamate clearance of 15 and 23 ml/min was calculated comprising only 9-15% of the hemoperfusion clearance. The amount of meprobamate removed by hemoperfusion ranged from 1.6-6.2 g. In one case, the half-life of plasma meprobamate during hemoperfusion was 2.6 hours compared to 8.3 hours after hemoperfusion. Thus the half-life was reduced more than 3-fold. These data show that hemoperfusion may be indicated in severe meprobamate intoxication.