Benzodiazepine Concentrations Research Articles

Objectively measured perinatal exposure to meperidine and benzodiazepines in Finland

We measured concentrations of meperidine and benzodiazepines in the umbilical serum of all live neonates born in Finland during a single week. Of the neonates, 31.1% were exposed to meperidine or benzodiazepines or both. One hundred twenty-one mothers of the 261 neonates exposed to meperidine were not recorded in the Finnish Medical Birth Registry as having received analgesic drugs. Infants born to primiparous mothers were more likely to be exposed. The exposures were associated with the type of delivery: vacuum extraction with a high proportion of neonates exposed to meperidine and elective caesarean section with a high proportion of neonates exposed to benzodiazepines. The exposures were influenced by the method of obstetric analgesia: epidural blockade was associated with more frequent exposure to meperidine. No significant circadian variation in exposures was detected. Validation of birth registry data is imperative before they are used for pharmacoepidemiologic studies.

Effects of Ca 2+ channel antagonists and benzodiazepine receptor ligands in normal and skinned rat urinary bladder

The effects of Ca 2+ channel antagonists and benzodiazepine receptor ligands against concentration-dependent contractions of rat urinary bladder induced by CaCl 2 (0.1–50 mM, in K +-depolarized tissues), KCl (1–100 mM) and acetylcholine (0.1 μM to 1 mM) were studied. Nifedipine (0.001–0.1 μM), verapamil (0.01–1 μM), diltiazem (0.01–1 μM), cinnarizine (1–100 μM), and trifluoperazine (1–100 μM) each produced a concentration-related inhibition of the log concentration-effect curve for CaCl 2. The rank order of potencies of these antagonists, measured as the IC 50 against Ca 2+ (25 mM)-induced contraction of depolarized bladder, was nifedipine (0.01 μM) > diltiazem (0.36 μM) ≈ verapamil (0.41 μM) ≥ cinnarizine (2.57 μM) > trifluoperazine (17.4 μM). These antagonists depressed KCl-induced contractions with an effectiveness and potency similar to that displayed against CaCl 2-induced contractions. Nifedipine, verapamil, and diltiazem but not cinnarizine and trifluoperazine had a preferential inhibitory effect on the contractions elicited by KCl when compared to those elicited by acetylcholine. Ro 5-4864, diazepam, midazolam and the non-benzodiazepine PK 11195, each at 1–100 μM, depressed CaCl 2- and KCl-induced contractions (IC 50 values in the micromolar range). Benzodiazepines and PK 11195, all at 100 μM, markedly depressed acetylcholine-induced contractions. Flumazenil was scarcely effective. Cinnarizine (100 μM) and trifluoperazine (100 μM), but not the other Ca 2+ channel antagonists and benzodiazepine receptor ligands tested, depressed Ca 2+ (20 μM)-evoked contractions of skinned bladder. It is concluded that the action of nifedipine, verapamil, and diltiazem is restricted to the plasmalemma whereas cinnarizine and trifluoperazine also act on the intracellular contractile apparatus. The inhibitory effects of micromolar concentrations of benzodiazepines appear to be related to an interaction with low-affinity sites functionally linked to L-type Ca 2+ channels but intracellular actions are present at high concentrations.

Flumazenil in cirrhotic patients in hepatic coma: A randomized double-blind placebo-controlled crossover trial†

Previous reports have suggested that "endogenous" benzodiazepines could contribute to neural inhibition in hepatic encephalopathy. RO 15-1788 (flumazenil), a specific antagonist of brain benzodiazepine receptors, could thus reverse the neurological symptoms of hepatic encephalopathy. To test this possibility, we conducted a double-blind, placebo-controlled crossover trial of the efficacy of flumazenil in cirrhotic patients in hepatic coma. Seventy-seven cirrhotic patients in hepatic coma were evaluated. Fifty-six were excluded from the trial because of multiorgan failure or because coma was precipitated by prior use of benzodiazepines, and 21 patients were randomly assigned to the flumazenil group (11 patients) or the placebo group (10 patients). Treatment was administered intravenously as a 20-ml solution (placebo or 2 mg flumazenil); seven patients were crossed over. Clinical status was assessed blindly by two observers, using a modified Glasgow scale, every 15 min for 6 hr. Electroencephalogram tracings obtained before and after drug administration were evaluated blindly by two independent observers. Serum concentrations of benzodiazepines before treatment were measured by means of a fluorescence polarization immunoassay. Improvement in neurological symptoms was observed in six patients treated with flumazenil, whereas none in the placebo group showed improvement (p < 0.05; Fisher's exact test). Improvements in electroencephalogram tracings were demonstrated in four patients treated with flumazenil, compared with two patients in the placebo group (p = NS). Benzodiazepines were found in the serum of four patients treated with flumazenil (two responders and two nonresponders); all of these patients had received pharmaceutical benzodiazepines 4 to 6 days before the trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous HPLC gradient analysis of 15 benzodiazepines and selected metabolites in postmortem blood.

The simultaneous identification and quantitation of 15 benzodiazepines and selected metabolites in postmortem blood, serum, or liver homogenate is described. The assay involves extraction with diethylether, followed by an acid clean-up step of the ether. Chromatographic separation was achieved on a Nova-Pak phenyl 18 column using ultraviolet detection at 240 nm. A gradient HPLC system was developed to improve separation of nitro-reduction metabolites from the solvent front and endogenous peaks. The mobile phases consisted of a gradient from 15 to 28% acetonitrile in 40 mM potassium phosphate buffer. Within-run and day-to-day precision were generally 10-15%. The method described is sensitive and reproducible for the analysis of benzodiazepine concentrations in postmortem tissues.

Mechanisms of activation of human mast cells and basophils by general anaesthetic drugs

A study was performed about the effects of increasing concentrations of muscle relaxants (suxamethonium, d-tubocurarine, vecuronium, and atracurium), hypnotics (propofol, ketamine, and thiopental), opioids (morphine, buprenorphine, and fentanyl), and benzodiazepines (diazepam, flunitrazepam, and midazolam) on the release of preformed (histamine and tryptase) and de novo synthesized (prostaglandin D 2 : PGD 2 and peptide-leukotriene C 4 : LTC 4) chemical mediators from human basophils and mast cells isolated from skin (HSMC), lung parenchyma (HLMC) and heart tissue (HHMC). None of the drugs tested induced the release of histamine or LTC 4 from basophils of normal donors. Suxamethonium did not induce mediator release from any type of human mast cell tested. Only the highest concentration of d-tubocurarine used caused histamine release from HSMC and HLMC. Atracurium, more than vecuronium, induced concentration-dependent histamine release from HSMC and HLMC. Propofol induced a concentration-dependent histamine release from HLMC, but not from HHMC. Only the highest concentrations of ketamine and thiopental used caused a significant release of histamine from HLMC. The muscle relaxants and hypnotics examined did not induce any de novo synthesis of PGD 2 or LTC 4 in mast cells. Morphine only induced histamine and tryptase release from HSMC, but not the de novo synthesis of PGD 2. In contrast, buprenorphine caused histamine and tryptase release from HLMC, and not from HSMC, whilst it also induced de novo synthesis of PGD 2 and LTC 4 in HLMC. Fentanyl did not give any histamine and tryptase release from mast cells. Diazepam and flunitrazepam only induced a small release of histamine from mast cells, whereas midazolam caused the release of histamine from HLMC. The biochemical pathways underlying the release of mediators from human mast cells induced by drugs used during general anaesthesia are different from those underlying the immune release of histamine. From the results obtained with the in vitro model described here, it is clear that new drugs promising for the anaesthesiologic arena should be tested in vitro before their potential histamine-releasing activity is experienced in vivo.

Confirmation of low concentrations of urinary benzodiazepines, including alprazolam and triazolam, by GC/MS: an extractive alkylation procedure.

Urine samples containing diazolo- and triazolobenzodiazepines and metabolites were hydrolyzed with beta-glucuronidase and extracted with methylene chloride. The extracts were treated with methyl iodide, methylene chloride, and tetrahexylammonium hydrogen sulfate in basic solution to form the methyl derivatives of the drugs and metabolites. GC/MS analysis resulted in the following test characteristics: day-to-day precision at 360 ng/mL (120 ng/mL for the triazolobenzodiazepine metabolites) was 2.4 to 5.5% CV; calibration curves were linear to 6000 ng/mL (1000 ng/mL for the triazolobenzodiazepine metabolites), and operational limits of quantitation were in the range 13-25 ng/mL.

Drug use and abuse in an urban veteran spinal cord injured population.

Substance abuse in the spinal cord injured (SCI) population has been addressed in a few controlled studies. These reports have led to the belief that many SCI patients were illicit drug users prior to their injury and that their drug abuse was a contributing cause of their accidents. One large study determined from answers obtained on a questionnaire that drug abuse, other than alcohol, was prevalent among injured veterans. Our study uses urine toxicology to determine the frequency of drug use and abuse, excluding alcohol, in 72 inpatients and 81 outpatients associated with an urban Veterans Affairs Medical Center. In a blinded experiment, urinary concentrations of opiates, barbiturates, amphetamines, methadone, benzodiazepines, and cocaine were determined with Syva reagents on an Abbott VP. Urinary cannabinoids were determined using Abbott TDX and the FPIA method. The use of illicit (unprescribed) drugs was surprisingly low (< or = 13 percent) for an urban medical center. Outpatient cannabinoid abuse was significantly more frequent than inpatient usage (p < 0.01). Barbiturates were not found in any patient. Benzodiazepines were taken most commonly (29 percent). Since benzodiazepine usage is the direct result of physician prescription, wide-spread usage of this agent is avoidable. Physicians should pay attention to the probable deleterious consequences of benzodiazepine addiction related to depressive effects on the central nervous system caused by its chronic use.

Development of methodology for analysis of brain function using radioisotope labeled compounds.

To evaluate the relationship between the pharmacological effect of benzodiazepine (BZP) and BZP receptor binding in the conscious mouse brain, a response of the glucose utilization (GU) to clonazepam (CNZ) was measured as an index for the pharmacological effect. GU was measured by the simultaneous use of [14C] 2-deoxyglucose (2DG), the glucose analogue which can be phosphorylated in the brain, and [3H] 3-O-methylglucose (3MG), the nonmetabolizable glucose analogue. The distribution volume of unphosphorylated 2DG in the brain was not significantly different from that of 3MG (VM), indicating that the phosphorylation rate of 2DG can be estimated by subtracting VM from apparent volume of distribution of 2DG. By this double tracer technique, it is possible to determine GU within 10min after administration of both tracers. Pharmacological and pathophysiological changes of the isotope correction factor (lumped constant) can also be estimated by this technique. In the cerebral cortex, GU decreased to 70 ?? 80% at 60 min after i.v. administration of CNZ (0.005 ?? 1.0mg/kg), and this effect was completely diminished by the administration of a benzodiazepine antagonist, Ro-15-1788 (5mg/kg). The maximum effect of CNZ on GU (about 30% decrease) was found at 0.1mg/kg of CNZ, but increasing the dose to 1mg/kg had very little additional effect. In vivo BZP receptor occupancy, measured using [3H] Ro-15-1788, increased from less than 10% at a dose of 0.005mg/kg up to essentially 100% at doses of 1mg/kg or greater. ID50 in dose response curve of the receptor occupancy for CNZ and ED50 in that of decrease in GU were 0.3mg/kg and 0.007mg/kg, respectively. A nonlinear and hyperbolic relationship was observed between the receptor occupancy and the response for the glucose metabolic rate, indicating that BZP exerts the maximum glucose metabolic change at a low fractional receptor occupancy (30 ?? 40%). By using positron emission tomography, these techniques can be applied to living human brain, which makes it possible to determine the optimal doses of BZP in the effective therapeutic drug monitoring. Furthermore, a mathematical allosteric coupling model has been proposed to des cribe the process by which binding to the GABA/benzodiazepine receptor complex initiates a biological response. The modeling exercise shows that the benzodiazepine concentration required for half-maximal biological response is lower than that required for half-maximal receptor binding. The degree of discrepancy between the two profiles (receptor occupancy and biological response) concerning benzodiazepine concentration dependency increased with the decrease in the dissociation constants based on the GABA receptor-benzod iazepine receptor interaction. This model offers a simple explanation for discrepancies between receptor occupancy-concentration profile of benzodiazepine and biological response-concentration curve that are often observed in vivo and/or in vitro.

Immunologische Untersuchungen auf Benzodiazepine—Der Einfluß von Strukturmerkmalen auf die Kreuzreaktivität ‐

The manufacturers' descriptions for immunoassays for the detection of benzodiazepines in urine suggest that all therapeutically used benzodiazepines are detected equally. It is unlikely that the different molecular structures do not influence the results of pertinent measurements. Therefore, the cross-reactivity of 35 benzodiazepines and benzodiazepine-metabolites was determined with the TDx-system. As compared to nordiazepam all compounds--except diazepam--had a reduced cross-reactivity. In order to get a TDx result equal to or exceeding 200 ng/ml nordiazepam-equivalents, high benzodiazepine concentrations in urine are required in some cases. These high concentrations are not obtained in the therapeutic range of application. These considerations can be applied to other immunoassays like RIA and EMIT.

Diagnostic utility of flumazenil in coma with suspected poisoning: A double blind, randomised controlled study

OBJECTIVE--To assess the diagnostic value and safety of the benzodiazepine antagonist flumazenil in patients with coma of unclear origin with suspected poisoning. DESIGN--Double blind, placebo controlled, randomised study. SETTING--Intensive care unit at a major teaching hospital. PATIENTS--105 Unconscious adults admitted consecutively with suspected drug overdosage during 18 months from a total of 362 cases of poisoning. Exclusion criteria were pregnancy, epilepsy, obvious poisoning with drugs identified unequivocally from information from relatives or others as other than benzodiazepines, and coma score greater than 10 on a scale graded from 4 to 20. Patients were allocated randomly to receive flumazenil (21 men and 32 women) or placebo (25 men and 27 women). INTERVENTIONS--Intravenous injection of flumazenil (10 ml, 0.1 mg/ml) or placebo (10 ml vehicle alone) given double blind over three minutes. MAIN OUTCOME MEASURES--Serum and urine concentrations of benzodiazepines, antidepressants, and several other agents; blood gas tensions; standardised evaluation on admission and five minutes after the injection by means of coma scale score and urgent diagnostic or therapeutic interventions indicated according to the history and clinical examination; standardised interview after the injection to try to ascertain further information; and adverse reactions. RESULTS--Benzodiazepines were found in the serum in 36 of the 53 patients in the flumazenil group and in 37 of the 52 who received placebo. The average coma scale score increased significantly after injection in the flumazenil group (6.4 v 12.1, p less than 0.001) but not in the placebo group. In the flumazenil group several interventions were rendered unnecessary by the injection: gastric lavage and urinary catheterisation (19 patients each), intubation (21), artificial ventilation and computed tomography of the brain (three patients each), blood culture and lumbar puncture (one patient each), and electroencephalography (two). In the placebo group the indications for these procedures did not change in any patient after injection. The 95% confidence interval for the difference in reduction of the frequency of indications for gastric lavage after injection between the two groups was 21% to 51%, that for intubation 25% to 55%, and that for urinary catheterisation 21% to 51%. In the flumazenil group 21 patients gave valuable information on their drug ingestion within 10 minutes after injection compared with only one in the placebo group (p less than 0.001). Nine adverse reactions were recorded in the flumazenil group, eight of which were graded as mild and one severe. The safety of the antagonist was acceptable, even though 60% of the patients in the flumazenil group had multiple drug poisoning including benzodiazepine. No epileptic seizures or arrhythmias were recorded. CONCLUSION--Flumazenil is a valuable and safe differential diagnostic tool in unclear cases of multiple drug poisoning.

Oral Contraceptive Drug Interactions

Interactions with oral contraceptives (OCs) occur with drugs commonly used to treat epilepsy, tuberculosis, and depression. Most women are more likely to use antibiotics, analgesics, and antihistamines, which have also been shown to interact with OCs. The mechanisms behind these interactions may be hepatic microsomal enzyme induction or inhibition, interference with the enterohepatic circulation of steroid metabolites, interference with absorption, competition between two drugs for the same metabolizing enzyme, or induction of an opposite physiologic effect. Rifampin was the first drug reported to interfere with the efficacy of OCs. The anticonvulsants and certain antibiotics, namely ampicillin and tetracycline, also decrease the efficacy of OCs. Oral contraceptives also interfere with the metabolism of other drugs. Plasma concentrations of theophylline, diazepam, and certain other benzodiazepines are increased by OC steroids. Because OCs interact with a wide variety of prescription and over-the-counter medications, a thorough drug history should be taken in all patients taking OCs.

Kinetic evaluation of pharmacological effects based on allosteric coupling of the benzodiazepine/gamma-aminobutyric acidA receptor in the brain.

A mathematical allosteric coupling model has been proposed to describe the process by which binding to the benzodiazepine/gamma-aminobutyric acid (GABA) receptor complex initiates a biological response. The model states that the first receptors (benzodiazepine receptors) can diffuse independently in the plane of the membrane and reversibly associate with the second receptors (GABA receptors) to regulate their activity (induction of increased chloride ion flux due to the opening of the chloride ion channel). The ratio of agonist-bound to total GABA receptor density was defined to be directly proportional to the biological response in the model. The analysis makes the following assumptions: i) the binding affinity of agonists (muscimol or benzodiazepine) to the benzodiazepine receptor/GABA receptor complex is much greater than that to each receptor alone; ii) the double receptor-single agonist (benzodiazepine, muscimol or GABA) ternary complex binds to the other agonist with a high binding affinity as compared with that of each agonist to an agonist-free receptor complex; iii) benzodiazepine receptor-GABA receptor interaction is enhanced in the presence of each agonist; iv) the GABA receptor is desensitized after the binding of GABA agonist (GABA or muscimol) to the receptor. The modeling exercise shows that the benzodiazepine concentration required for half-maximal biological response is lower than that required for half-maximal receptor binding. In the case of the GABA agonist, a linear relationship between receptor occupancy and biological response was observed. The degree of discrepancy between the two profiles (receptor occupancy and biological response) concerning benzodiazepine concentration dependency and time dependency increased with a decrease in the dissociation constants based on the benzodiazepine receptor-GABA receptor interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Actions of insecticides on the insect GABA receptor complex.

The actions of insecticides on the insect gamma-aminobutyric acid (GABA) receptor were investigated using [35S]t-butylbicyclophosphorothionate [( 35S]TBPS) binding and voltage-clamp techniques. Specific binding of [35S]TBPS to a membrane homogenate derived from the brain of Locusta migratoria locusts is characterised by a Kd value of 79.3 +/- 2.9 nM and a Bmax value of 1770 +/- 40 fmol/mg protein. [35S]TBPS binding is inhibited by mM concentrations of barbiturates and benzodiazepines. In contrast dieldrin, ivermectin, lindane, picrotoxin and TBPS are inhibitors of [35S]TBPS binding at the nanomolar range. Bicuculline, baclofen and pyrethroid insecticides have no effect on [35S]TBPS binding. These results are similar to those obtained in electrophysiological studies of the current elicited by GABA in both Locusta and Periplaneta americana central neurones. Noise analysis of the effects of lindane, TBPS, dieldrin and picrotoxin on the cockroach GABA responses reveals that these compounds decrease the variance of the GABA-induced current but have no effect on its mean open time. All these compounds, with the exception of dieldrin, significantly decrease the conductance of GABA-evoked single current.

Diagnostic utility of flumazenil in coma with suspected poisoning: a double blind, randomised controlled study.

To assess the diagnostic value and safety of the benzodiazepine antagonist flumazenil in patients with coma of unclear origin with suspected poisoning. Double blind, placebo controlled, randomised study. Intensive care unit at a major teaching hospital. 105 Unconscious adults admitted consecutively with suspected drug overdosage during 18 months from a total of 362 cases of poisoning. Exclusion criteria were pregnancy, epilepsy, obvious poisoning with drugs identified unequivocally from information from relatives or others as other than benzodiazepines, and coma score greater than 10 on a scale graded from 4 to 20. Patients were allocated randomly to receive flumazenil (21 men and 32 women) or placebo (25 men and 27 women). Intravenous injection of flumazenil (10 ml, 0.1 mg/ml) or placebo (10 ml vehicle alone) given double blind over three minutes. Serum and urine concentrations of benzodiazepines, antidepressants, and several other agents; blood gas tensions; standardised evaluation on admission and five minutes after the injection by means of coma scale score and urgent diagnostic or therapeutic interventions indicated according to the history and clinical examination; standardised interview after the injection to try to ascertain further information; and adverse reactions. Benzodiazepines were found in the serum in 36 of the 53 patients in the flumazenil group and in 37 of the 52 who received placebo. The average coma scale score increased significantly after injection in the flumazenil group (6.4 v 12.1, p less than 0.001) but not in the placebo group. In the flumazenil group several interventions were rendered unnecessary by the injection: gastric lavage and urinary catheterisation (19 patients each), intubation (21), artificial ventilation and computed tomography of the brain (three patients each), blood culture and lumbar puncture (one patient each), and electroencephalography (two). In the placebo group the indications for these procedures did not change in any patient after injection. The 95% confidence interval for the difference in reduction of the frequency of indications for gastric lavage after injection between the two groups was 21% to 51%, that for intubation 25% to 55%, and that for urinary catheterisation 21% to 51%. In the flumazenil group 21 patients gave valuable information on their drug ingestion within 10 minutes after injection compared with only one in the placebo group (p less than 0.001). Nine adverse reactions were recorded in the flumazenil group, eight of which were graded as mild and one severe. The safety of the antagonist was acceptable, even though 60% of the patients in the flumazenil group had multiple drug poisoning including benzodiazepine. No epileptic seizures or arrhythmias were recorded. Flumazenil is a valuable and safe differential diagnostic tool in unclear cases of multiple drug poisoning.

Benzodiazepine concentrations in brain directly reflect receptor occupancy: studies of diazepam, lorazepam, and oxazepam

Groups of male CF-1 mice received 3 and 10 mumol/kg diazepam, lorazepam, and oxazepam intravenously. Between 1 min and 24 h after injection, benzodiazepine concentrations were determined by gas chromatography (GLC) in plasma and in one brain hemisphere; in the other hemisphere, ex vivo benzodiazepine receptor occupancy was measured using 3H-flunitrazepam displacement. Based on GLC data, diazepam entered brain rapidly, and was also cleared rapidly, yielding desmethyldiazepam and oxazepam as metabolites in plasma and brain. However, lorazepam and oxazepam entered brain slowly, with brain:plasma equilibrium achieved at 30-60 min; thereafter, the drugs were eliminated from plasma and brain in parallel. The time course and extent of ex vivo occupancy were highly consistent with GLC data (for diazepam, GLC levels were expressed as the sum of diazepam, desmethyldiazepam, and oxazepam, with metabolite concentrations, normalized for molecular weight and for in vitro benzodiazepine receptor affinity.) Between-method correlations were 0.95 or higher. Thus benzodiazepine receptor occupancy is highly dependent on benzodiazepine concentrations in brain. Differences in the time-course of onset and duration of pharmacologic activity between the highly lipophilic benzodiazepine diazepam and the less lipophilic hydroxylated derivatives lorazepam and oxazepam are largely explained by differences in systemic kinetics and in the rate of uptake into brain.

Brain concentrations of benzodiazepines are elevated in an animal model of hepatic encephalopathy.

Brain extracts from rats with hepatic encephalopathy due to thioacetamide-induced fulminant hepatic failure contained 4- to 6-fold higher concentrations of substances that inhibit radioligand binding to benzodiazepine receptors than corresponding control rat extracts. Both isocratic and gradient-elution HPLC indicated that this inhibitory activity was localized in 3-8 peaks with retention times corresponding to deschlorodiazepam, deschlorolorazepam, lorazepam, oxazepam, diazepam, and N-desmethyldiazepam. The presence of diazepam and N-desmethyldiazepam was confirmed by mass spectroscopy. Both mass spectroscopic and radiometric techniques indicated that the concentrations of N-desmethyldiazepam and diazepam in brain extracts from encephalopathic rats were 2-9 and 5-7 times higher, respectively, than in control brain extracts. While benzodiazepines have been identified previously in mammalian and plant tissues, this report demonstrates that concentrations of these substances are increased in a pathophysiological condition. These findings provide a rational basis for the use of benzodiazepine receptor antagonists in the management of hepatic encephalopathy in humans.

Stimulation of cell growth and DNA synthesis by peripheral benzodiazepine

The effects of peripheral benzodiazepine receptor ligands on cell proliferation were evaluated. PK11195 increased the growth rate of C6 glioma cells by 20–30% in the nanomolar range in serum free medium. [ 3H]thymidine incorporation into C6 glioma cells also were increased 22% and 25% after treatment by PK11195 and Ro5-4864, respectively. The effect of PK11195 as a mitogenic agent was estimated by [ 3H]thymidine incorporation using Swiss 3T3 cells. PK11195 increased DNA synthesis 170% over control at 10 nM. Higher concentrations of benzodiazepines showed inhibition of the DNA synthesis. Peripheral benzodiazepine binding sites underwent downregulation after exposure to serum free medium or to 10 nM PK11195. These findings suggest that peripheral benzodiazepines may be involved in the regulation of cell proliferation as a growth factor in lower concentration and as a antiproliferative agent in higher concentration.

A Clinical Scale to Assess Benzodiazepine Withdrawal

The objective, sensitive, and reliable quantitation of withdrawal symptoms is essential to assess physical dependence on drugs. Data collected from 23 patients abusing high doses of benzodiazepines (mean diazepam dose equivalents, 150 mg/day; range, 40-500) and from 40 long-term therapeutic users randomized to receive either placebo (N = 19) or diazepam (N = 21; mean diazepam dose equivalents, 15 mg/day; range, 5-40; mean duration of use, 72 months; range, 6-240) were analyzed. Information on the type and severity of symptoms was obtained from several assessment instruments. In the high-dose abuse group, plasma benzodiazepine concentrations were measured daily and the 3 consecutive days of greatest relative daily fall were considered the critical withdrawal period. Selection of the 22 items of the Clinical Institute Withdrawal Assessment-Benzodiazepines (CIWA-B) was based on statistically significant differences between baseline and critical withdrawal periods in high-dose subjects and between symptoms associated with placebo and diazepam in low-dose subjects, using contingency tables and logistic regression analysis. Of the 104 symptoms measured by the assessment instruments, 22 symptoms were found to distinguish withdrawal from prewithdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of the Newer Benzodiazepines

The assay methods used to determine the concentrations of the newer benzodiazepines include electron-capture gas-liquid chromatography, high performance liquid chromatography with ultraviolet detection, gas chromatography-mass spectrometry, radioassay and radioreceptor assay. The method used frequently is the highly sensitive and specific electron-capture gas-liquid chromatography. Other methods are associated with limitations. The triazolo- and imidazolebenzodiazepines differ structurally from the 'classical' benzodiazepines such as diazepam, and offer distinct differences in pharmacological activity and in time-course of effect. Alprazolam and triazolam, both 1,4-triazolobenzodiazepines, have high affinities for the benzodiazepine receptor as do midazolam and loprazolam, which are 1,4-imidazolebenzodiazepines. Absorption is characteristically rapid, with peak alprazolam and triazolam concentrations occurring within 1 hour after oral administration. Sublingual administration results in peak alprazolam and triazolam concentrations that are higher and occur earlier than with the oral route. The volume of distribution of alprazolam and triazolam is approximately 1L. Alprazolam is 70% bound to plasma proteins and the extent of binding is independent of concentration. Similarly, triazolam is approximately 85% bound to plasma proteins, variability in binding being explained by variations in alpha 1-acid glycoprotein concentration. The 1,4-triazolo ring prevents the oxidative metabolism of the classical benzodiazepines which results in formation of active metabolites with long elimination half-lives. Alprazolam is extensively metabolised: 29 metabolites have been identified in the urine, and its major metabolite, alpha-hydroxyalprazolam, has pharmacological activity. alpha-Hydroxyalprazolam and 4-hydroxyalprazolam are detectable in plasma in amounts which account for less than 10% of the administered dose. Mean alprazolam elimination half-life in healthy adult subjects ranges from 9.5 to 12 hours; liver disease prolongs alprazolam elimination, but renal insufficiency does not. Triazolam also undergoes oxidation and subsequent glucuronidation. alpha-Hydroxytriazolam is the major metabolite, in addition to which 4-hydroxyalprazolam and alpha-4-hydroxytriazolam have been identified in plasma and urine. The elimination half-life of triazolam ranges between 1.8 and 5.9 hours, while that of the conjugated metabolites is short, approximately 3.8 hours. Accumulation of triazolam or its metabolites after multiple doses does not occur. Liver disease prolongs triazolam elimination from the body, but renal disease does not.(ABSTRACT TRUNCATED AT 400 WORDS)

Interference of common household chemicals in immunoassay methods for drugs of abuse.

I report how some adulterants affect results for drugs of abuse in urine as measured by Roche RIA, Syva emit d.a.u., and Abbott TDx fpia (fluorescence polarization immunoassay) for the following drugs: amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, opiates, and phencyclidine (PCP). Sodium chloride interfered negatively with all of these drugs when assayed by emit and caused a slight decrease in measured benzodiazepine concentration by fpia. Drug concentrations were also decreased by added H2O2 (emit: benzodiazepine), Joy detergent (emit: cannabinoid, benzodiazepines, PCP), NaHCO3 (emit: opiate; fpia: PCP), or NaClO [corrected] (emit, RIA, fpia: amphetamines, opiates, PCP; emit, fpia: cannabinoid; emit: benzodiazepines). False-positive results were caused by H2O2 (fpia: benzodiazepines) and Joy (RIA, fpia: benzodiazepine, cannabinoid; fpia: barbiturate, amphetamine). Sodium bicarbonate causes a suspiciously high pH in the urine, NaClO [corrected] an apparently low pH (using pH paper).