Improved insulin stability through amino acid substitution

Insulin analogs designed to decrease self-association and increase absorption rates from subcutaneous tissue were found to have altered stability. Replacement of HB10 with aspartic acid increased stability while substitutions at B28 and/or B29 were either comparable to insulin or had decreased stability. The principal chemical degradation product of accelerated storage conditions was a disulfide-linked multimer that was formed through a disulfide interchange reaction which resulted from beta-elimination of the disulfides. The maintenance of the native state of insulin was shown to be important in protecting the disulfides from reduction by dithiothreitol and implicitly from the disulfide interchange reaction that occurs during storage. To understand how these amino acid changes alter chemical stability, the intramolecular conformational equilibria of each analog was assessed by equilibrium denaturation. The Gibbs free energy of unfolding was compared with the chemical stability during storage for over 20 analogs. A significant positive correlation (R2 = 0.8 and P less than 0.0005) exists between the conformational stability and chemical stability of these analogs, indicating that the chemical stability of insulin's disulfides is under the thermodynamic control of the conformational equilibria.

Pharmacodynamics of three daily infusions of etoposide in patients with extensive-stage small-cell lung cancer

The objectives of this study were to define the pharmacodynamics of etoposide and to develop potentially useful models (1) to estimate the plasma clearance using a limited number of samples and (2) to describe the relationship between clearance and the dose-limiting toxicity. A total of 17 patients with extensive-stage small-cell lung cancer were treated with 150 mg/m2 etoposide daily for 3 consecutive days and with 100 mg/m2 cisplatin on day 3 only. Both drugs were given intravenously over 1 h. Treatment was repeated every 21 days for up to six courses. All patients were newly diagnosed (no previous chemotherapy or irradiation) and had a performance status of 0-2. Six patients achieved a complete response as confirmed by repeat bronchoscopy and five patients showed a partial response, for an overall objective response rate of 65% (95% confidence interval, 38%-87%). The median survival was 8 months (range, 1-24+ months). The dose-limiting toxicity was neutropenia. Etoposide pharmacokinetics were measured during the first course and determinations were repeated during courses 3 or 4 and 6. Complete blood counts were obtained weekly. Correlations for etoposide clearance and hematologic toxicities were evaluated for 17 initial courses and for an overall number of 33 courses. Pharmacodynamic correlations were significant for graded hematologic toxicities, as well as nadirs of leukocytes, neutrophils, and platelets for the initial courses and for all courses. To reduce the requirement for numerous blood samples, a limited sampling model was developed to estimate the area under the concentration versus time curve (AUC) with the following equation: AUC = 15.45 + 3.86 x C2 + 7.10 x C4, where C2 and C4 represent the etoposide concentrations at 2 and 4 h, respectively. The total plasma clearance was calculated as the dose divided by the AUC; correlations with toxicity were better for clearance expressed in milliliters per minute than for that expressed in milliliters per minute per square meter of body surface area. The absolute neutrophil count at the nadir (ANCn) can be estimated by the following pharmacodynamic model, which is based on 33 courses: ANCn = -0.399 + 0.024 x Ecl, where Ecl represents the etoposide clearance expressed in milliliters per minute. Further studies are necessary to validate both models prospectively.

Further characterization of the loop structure of platelet glycoprotein IIIa: partial mapping of functionally significant glycoprotein IIIa epitopes

Glycoprotein (GP) IIb-IIIa serves as the platelet fibrinogen receptor. Studies of the tertiary structure of GPIIIa have shown that the protein has a large loop structure of at least 325 amino acids in length. To further characterize this loop structure, intact platelets were digested with alpha-chymotrypsin. Digestion products were examined using the anti-GPIIIa monoclonal antibodies (MoAbs) AP3, D3GP3, and C5GP3, as well as the human alloantibody, anti-PLA1. AP3 recognized GPIIIa digestion products of 109, 95, and 68 Kd. D3GP3 and C5GP3 recognized an additional band of 51 Kd. Time course digestions demonstrated that the 51-Kd fragment was generated by proteolysis of the 68-Kd peptide. Sequence analysis of the reduced 51-Kd peptide showed that this fragment began at amino acid 422. The nonreduced 51-Kd peptide was reactive with antibodies directed against the first 13 amino acids of GPIIIa, demonstrating the presence of a covalently attached N-terminal peptide. These data suggest that: (1) the minimum length of the loop structure is at least 384 amino acids; (2) the AP3 epitope is formed at least in part by a determinant contained within residues 348 to 421; and (3) the D3GP3 and C5GP3 epitopes are contained within amino acids 422 to 692 of GPIIIa, a region that may be flexible and involved in conformational changes that occur after ligand binding.

The effect of lamotrigine upon development of cortical kindled seizures in the rat

The effect of lamotrigine, a novel potential antiepileptic drug, upon the development of kindled cortical seizures was investigated in rats. Although lamotrigine, at all doses tested, failed to block or reduce the rate of development of kindling, it did have a profound effect upon the production of both non-kindled and kindled responses. All doses (3, 6, 12 and 18 mg/kg) produced a significant increase in the number of nil responses (where stimulation failed to evoke a behavioural clonus or afterdischarge) and a decrease in non-kindled responses. Doses of 12 and 18 mg/kg also significantly reduced the number of kindled responses and the duration of the kindled seizure. It is suggested that these effects of lamotrigine result from its ability to inhibit the release of glutamate, an excitatory amino acid which has been implicated in the production of kindled seizures. In contrast to previous studies on the development of kindling, it was found that in the groups which received either 12 or 18 mg/kg lamotrigine, it was possible to produce kindling without evoking any nonkindled afterdischarge. This finding is discussed in the light of the current theories surrounding the kindling process. This study suggests that lamotrigine, as well as possibly being of value in the treatment of complex partial and generalised (tonic-clonic) seizures, may also be of value in the treatment of elementary (simple) partial seizures.

[Functional morphology of gastrin-producing cells in different phases of periodic gastric activity in dogs]

Gastrin producing cells of mucosal stomach antrum have been studied in different phases of periodical stomach activity and starvation. It has been established that functional morphology of gastrin producing cells were variable in different phases of stomach activity that coincides with the levels of gastrin in systemic blood stream.

Clinical pharmacodynamics of continuous-infusion etoposide

Continuous-infusion etoposide was given to 15 patients with newly diagnosed small-cell lung cancer (extensive disease) and 10 patients with various refractory malignancies. The untreated patients with lung cancer received 200 mg/m2 etoposide over 24 h in combination with 100 mg/m2 cisplatin, and the pretreated patients received 400 mg/m2 etoposide over 36 h as monotherapy. Pharmacokinetic studies of etoposide were carried out in all patients. High-performance liquid chromatography (HPLC) was used to measure etoposide. All patients had normal hepatic and renal function tests and were followed weekly for hematologic toxicity after therapy. In all, 14 untreated and 9 pretreated patients were evaluable. Biostatistical analysis was done to correlate pharmacokinetic results to hematologic effects. Pearson correlation coefficients were calculated for continuous variables (i.e., blood counts), and Spearman correlation coefficients were calculated for ranked variables (i.e., toxicity grades). The values for the area under the plasma concentration vs time curve (AUC) and systemic clearance varied widely among patients. However, the AUC and clearance were significantly correlated (P less than 0.05) with the WBC and platelet nadirs and the decrease in hemoglobin. The grade of leukopenia and total grade of hematologic toxicity were also correlated with AUC and clearance. Because the interpatient variability in etoposide pharmacokinetics correlates with the variable degree of hematologic toxicity, pharmacokinetic drug monitoring is suggested.

High-dose medroxyprogesterone acetate in advanced breast cancer. Clinical and pharmacokinetic study with a combined oral and intramuscular regimen

Seventy-five patients with advanced and intensively pretreated breast cancer received high-dose medroxyprogesterone acetate (MPA) using a schedule consisting of an intramuscular (IM) loading dose (1 g MPA IM days 1 to 10) and an oral maintenance treatment (200 mg/day three times a day) thereafter. A reinduction was performed in part of the responding patients at time of early relapse (1 g MPA IM for 10 consecutive days). MPA serum levels above 100 ng/ml were achieved during induction treatment and maintained for 3 to 4 months during the oral phase of therapy before decreasing to approximately 50 ng/ml. Two complete remissions (duration, 17.2 and 62 months), 15 partial remissions (median duration, 7 months), and 21 cases of disease stabilization (median duration, 5.5 months) were achieved. The median survival time was significantly longer for responders (19.9 months) than nonresponders (4.8 months). Although a higher proportion of postmenopausal patients responded, the remission duration in premenopausal women was remarkably long. Favorable sites of response were soft tissue, lymph nodes, and bone lesions. Reinduction treatment yielded a second response (two partial remissions, three no change) in five of six patients indicating that high-dose conditions were necessary to maintain response. This schedule allows to restrict higher doses of MPA on a long-term basis to responding patients.

Etoposide: an update

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and pharmacodynamics of etoposide are reviewed. Etoposide, although similar in chemical structure to podophyllotoxin, has a different mechanism of cytotoxicity compared with its parent compound. Etoposide may stabilize type II topoisomerase-DNA complexes, preventing rejoining of single- and double-strand DNA breaks. Etoposide may also require cellular activation into intermediates, which then bind to DNA and disrupt cellular function. Oral etoposide has an average bioavailability of 50% (range, 17%-137%), with substantial intrapatient and interpatient variability. Etoposide is widely distributed in the body and is highly bound to plasma proteins (greater than 95%). Approximately 50% (range, 20%-81%) of an etoposide dose is recovered in the urine as parent drug or glucuronide, with the remainder of the dose being unaccounted for. The disposition of etoposide in patients with renal and hepatic dysfunction is discussed. Etoposide is effective in combination with other agents against lung cancer, and response rates of 90% in small-cell lung cancer have been observed. When etoposide is used in combination with other agents, response rates of approximately 80% have been observed in patients with testicular cancer. The activity of etoposide in treating leukemia, lymphoma, and breast and ovarian carcinomas and other tumors is discussed. The impact of etoposide on prolonging survival in lung and testicular cancer is addressed, and studies evaluating the pharmacodynamics of etoposide are described. Adverse effects associated with etoposide therapy include myelosuppression, alopecia, nausea and vomiting, mucositis, and hypotension after rapid intravenous administration. Etoposide has demonstrated considerable clinical efficacy against a broad spectrum of tumors.

Effects of lamotrigine on electrically induced afterdischarge duration in anaesthetised rat, dog, and marmoset

The effects of lamotrigine (LTG), a novel potent anticonvulsant, following intravenous (i.v.) bolus injection were studied on the durations of electrically induced afterdischarges of the EEG in halothane-anaesthetised dogs and marmosets, species used in toxicity studies. For comparison, the effect of LTG on hippocampal afterdischarge duration was also studied in halothane anaesthetised rats, a species in which the anticonvulsant action of LTG has been widely investigated. The known anticonvulsants phenytoin (PHT) and phenobarbital (PB) were included for comparison. LTG reduced afterdischarge duration in a dose-dependent manner in rat and dog; it was approximately twofold more potent than PHT in the dog and three- to fourfold more potent than PB in both dog and rat (LTG ED50 values = 4.5 and 11.7 mg.kg-1 i.v. in dogs and rats, respectively). PHT was ineffective in the rat at sublethal doses (less than 40 mg.kg-1 i.v.). In limited studies in marmosets, i.v. administration of both LTG and PHT (both 5-15 mg.kg-1) reduced or abolished afterdischarge. Thus, LTG was a potent anticonvulsant in rat, dog, and marmoset in afterdischarge models of partial (focal) seizures and may be of utility in the treatment of partial seizures in humans.

Hippocampal NMDA/phencyclidine receptor binding sites are reduced following forebrain ischaemia in the gerbil

The binding of [3H]N-(1-[2-thienyl]cyclohexyl)piperidine (TCP) to N-methyl-D-aspartate (NMDA) receptor sites in synaptic membranes prepared from the dorsal hippocampus of the ischaemic gerbil, has been studied. Forebrain ischaemia was induced by 10 min bilateral carotid occlusion and receptor binding determined in the dorsal hippocampus 1 week later. [3H]TCP binding capacity was significantly reduced by 28% in ischaemic tissue with no change in affinity. This result is consistent with the involvement of NMDA receptors in ischaemic brain damage.

Plasma concentrations of medroxyprogesterone acetate and megesterol acetate during long-term follow-up in patients treated for metastatic breast cancer

A total of 32 patients with metastatic breast cancer responding with at least disease stabilization to treatment with two commercially available preparations of medroxyprogesterone acetate (MPA) or one preparation of megestrol acetate (MA) were followed for their plasma concentrations. The MPA and MA were measured by HPLC. MPA from Upjohn and Farmitalia was given to 12 patients (median age, 61 years; median follow-up, 20 weeks) and 8 patients (54 years, 16 weeks), respectively, on a schedule of 1000 mg daily i.m. for 10 days followed by 200 mg t.i.d.p.o. for the remainder of the treatment course. The peak concentrations (means, 163 vs 97 ng/ml), the time to peak levels (medians, 3 vs 10 weeks), and the areas under the concentration curves from time 0 to 24 weeks (means, 2400 vs 1868 ng/ml X weeks) were significantly different in the respective treatment groups (t-test; significance level, 0.05). MA from Bristol-Myers was administered orally in one daily dose of 160 mg throughout the treatment course in 12 patients (median age, 51 years; median follow-up, 20 weeks). A mean MA peak concentration of 218 ng/ml was reached after a median of 7 days. Plateau plasma levels were higher for MA than MPA.

Phase I study of pirarubicin

A Phase I trial of pirarubicin (4'-O-tetrahydropyranyl-doxorubicin) was undertaken to study its toxicity and to gain preliminary knowledge of its efficacy. The dose was escalated by increments of 10 from 30 to 70 mg/m2. Out of 20 patients, 19 were evaluable for toxicity and response to treatment. Hematologic toxicity was dose limiting and dose related. Other adverse effects included nausea and vomiting, hair loss, and stomatitis. No acute cardiotoxicity was encountered. In 2 patients with metastatic breast cancer who had not been pretreated with cytostatic agents, a partial remission was achieved lasting for 5 months. In 6 patients, tumor parameters did not change for a median of 3 months, and 11 patients suffered progressive disease.

Clinical pharmacology of aminoglutethimide in patients with metastatic breast cancer

The pharmacology of aminoglutethimide (AG) was studied in two subsequent trials without hydrocortisone supplementation. A total of 79 patients with metastatic breast cancer entered the study, and their plasma and urine samples were analyzed by high-performance liquid chromatography (HPLC). Thirty evaluable patients with a median age of 57 years (range, 37-79) were treated with the standard dose of 1000 mg/day, and 37 evaluable patients with a median age of 59 years (range, 35-79) received 500 mg/day. The median follow-up in the two groups was 5 months (range, 1-16) and 4 months (range, 1-21), respectively. After the first oral dose of 500 mg, peak plasma concentrations of AG were observed 1-4 h after administration in 15 patients. The elimination half-life was 10.1 +/- 1.7 h (mean +/- SD) after initial dosage; it decreased significantly to 6.9 +/- 1.2 h after 8 weeks of treatment. The area under the curve of AG concentrations was 92.5 +/- 14.2 micrograms/ml x h. The total clearance rate was 5.5 +/- 0.9 1/h and the volume of distribution was 80 +/- 111. About 23% of the drug was excreted unchanged in the urine. The major metabolite, N-acetyl-AG (AAG), had the same half-life as AG. A comparison on day 7 of treatment revealed that doses of 1000 and 500 mg yielded AG plasma concentrations of 9.0 +/- 1.2 and 4.5 +/- 0.5 micrograms/ml, respectively. After 1 month of treatment, however, AG plasma levels of 6-7 and 4-5 micrograms/ml were observed, respectively. A 50% reduction of dose, therefore, resulted in only 30% lower AG levels during continuous treatment. Apparently, the induction of metabolism is of greater importance in standard-dose than in lower dose treatment. The plasma concentrations of AG did not bear a relationship to the clinical response.

Clinical pharmacology of sodium butyrate in patients with acute leukemia

Since cancer may be regarded as a disease of differentiation and sodium butyrate induces differentiation of malignant cells in vitro, a study of the clinical pharmacology of sodium butyrate was undertaken. Nine patients with acute myeloid (n = 1), acute monocytic (n = 1), acute myelomonocytic (n = 6) and acute undifferentiated (n = 1) leukemia were treated. Their median age was 52 (range, 27-78) years. Six of the nine patients were pretreated with cytostatic agents. Sodium butyrate was administered i.v. at a dosage of 500 mg/kg/day as continuous infusion over 10 days. A sensitive and reproducible high-performance liquid chromatographic separation was developed after derivatization of sodium butyrate with 2,4'-dibromoacetophenone employing crown ether catalysis. Plasma concentrations and urinary excretion of sodium butyrate were monitored during the 10 days of continuous infusion and for 2 days thereafter. During infusion, plasma concentrations increased 6-fold over the endogenous butyrate level and reached 39-59 microM. The area under the curve of the exogenous butyrate was 384 +/- 50 microM X day (mean +/- S.D.). After the end of infusion, concentrations declined rapidly with a half-life of 6.1 +/- 1.4 min, and reached pretreatment values within 1 hr. The total clearance rate was 83 +/- 12 ml/kg/min and the volume of distribution 738 +/- 245 ml/kg. The excreted amounts of butyrate in the urine were minimal as compared to the infused dose. Although excretion by other organs was not ruled out, it is suggested that the infused sodium butyrate was rapidly metabolized. A significant increase in peripheral blast cells was observed, whereas bone marrow cytologies before and after treatment did not reveal a significant change in blasts. Differential counts of peripheral white blood cells did not show significant changes. No toxicity was encountered. The apparent lack of clinical efficacy may be explained by the low plasma levels of sodium butyrate due to its short half-life in vivo. In comparison, concentrations reported for in vitro studies were at least 10 times higher.

Clinical pharmacology and toxicity of 4'-O-tetrahydropyranyladriamycin

The clinical pharmacology and toxicity of a novel anthracycline derivative, 4'-O-tetrahydropyranyladriamycin (THP-adriamycin), was investigated in patients with advanced malignant diseases. The starting dose was 30 mg/m2 which was escalated by increments of 10 mg/m2. Twelve patients with a median age of 42 (range, 19-69) years and a median Eastern Cooperative Oncology Group performance score of 2 (range, 1-2) were entered into the study. The diagnoses included four testicular cancers, two breast cancers, two small cell lung cancers, two acute myeloid leukemias, one colon cancer, and one hemangiosarcoma. THP-adriamycin was given as an i.v. bolus injection every 3 weeks. Evaluable were 18 courses for general toxicity, 16 courses for hematological toxicity, and 16 courses for pharmacokinetics. THP-adriamycin had a short initial half-life of 1.4 +/- 0.3 min (mean +/- SD) due to rapid cellular uptake. Peak concentrations in unseparated blood cells were reached 5 min after drug injection and remained higher than in plasma throughout the observation period of 72 h. The half-lives of THP-adriamycin in plasma were 19 +/- 2.8 min in an intermediate and 13 +/- 1.6 h in the terminal phase. A linear correlation was observed between the dose and the areas under the concentration curves for THP-adriamycin in plasma (r2 = 0.97) and blood cells (r2 = 0.99). The volume of distribution was 2124 +/- 221 liters/m2 and the total clearance rate 115 +/- 11 liters/m2h. THP-adriamycin was metabolized to Adriamycin, THP-adriamycinol, and adriamycinol. The major metabolite was Adriamycin with a terminal half-life in plasma of 33 +/- 10 h. The area under the curve of Adriamycin was also correlated to the administered dose (r2 = 0.96). Since excessive peak concentrations of Adriamycin were avoided, the treatment with THP-adriamycin might be an alternative to continuous infusions or weekly administrations. The maximum tolerated dose was 70 mg/m2, and the dose-limiting toxicities were leukopenia and thrombocytopenia. Anemia, nausea, and vomiting were mild to moderate, and no other toxicity was observed. All side effects were dose dependent and reversible. In a patient with breast cancer, a disease stabilization was achieved lasting for 9 weeks. No objective remission was observed. We suggest 60 mg/m2 in pretreated or poor risk and 70 mg/m2 in untreated or good risk patients every 3 weeks for further clinical trials.

Effect of cortical kindling on [3H]D-aspartate uptake and glutamate metabolism in rats

The effects of cortical kindling in rats on [3H]D-aspartate uptake and on glutaminase and glutamine synthetase activities has been studied. The high affinity uptake of [3H]D-aspartate in control cortical tissue (Km approximately 2 microM) was undetectable in the kindled tissue, whilst the enzyme activities were unchanged. A loss of the high-affinity uptake sites for excitatory amino acids may be a contributing factor to the kindling phenomenon.

Cardiovascular and neurological effects of laudanosine. Studies in mice and rats, and in conscious and anaesthetized dogs

The effects of laudanosine, a metabolite of atracurium, on the behaviour of conscious mice, rats and dogs, and on cardiovascular function in conscious and anaesthetized dogs have been evaluated: EEG studies were performed in anaesthetized dogs. In mice and rats, i.v. bolus doses of laudanosine 10-20 mg kg-1, caused convulsions and hind limb extensions; these effects were prevented by pretreatment with diazepam. After the continuous infusion of laudanosine to conscious dogs, plasma concentrations in the order of 1.2 micrograms ml-1 did not cause behavioural disturbances. In anaesthetized dogs, laudanosine plasma concentrations of more than 6 micrograms ml-1 caused hypotension and bradycardia, laudanosine concentrations greater than 10 micrograms ml-1 induced epileptic EEG spiking and plasma concentrations greater than 17 micrograms ml-1 produced prolonged seizures. There is a wide difference between laudanosine plasma concentrations in patients given atracurium by bolus injection or by short-term infusion for surgical use and those required to induce epileptic activity in dogs. However, during the prolonged infusion of atracurium to patients this difference will be decreased. It is unlikely that the use of atracurium, in patients, would result in plasma concentrations of laudanosine capable of producing neurological or cardiovascular disturbances.

Pharmacological studies on lamotrigine, a novel potential antiepileptic drug: II. Neurochemical studies on the mechanism of action

Lamotrigine (LTG) [3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine] is a novel anticonvulsant chemically unrelated to current antiepileptic drugs and with a pharmacological profile similar to that of phenytoin. The effect of LTG has been compared with that of phenytoin, on the release of endogenous amino acids and radiolabelled acetylcholine evoked by veratrine or potassium, from slices of rat cerebral cortex in vitro. Both veratrine and potassium evoked a marked release of glutamate and gamma-aminobutyric acid (GABA), with a more moderate release of aspartate. LTG inhibited veratrine-evoked release of glutamate and aspartate, with ED50 values of 21 microM for both amino acids, but LTG was less potent in the inhibition of GABA release (ED50 = 44 microM). At concentrations up to 300 microM, LTG had no effect on potassium-evoked amino acid release or on spontaneous release. Also, LTG was some five times less potent in the inhibition of veratrine-evoked [3H]acetylcholine release (ED50 = 100 microM) than in glutamate or aspartate release. The total lack of effect of LTG on potassium-evoked release and the potent effect on veratrine-evoked release (at concentrations found in rat brain after anticonvulsant doses) strongly suggest that LTG acts at voltage-sensitive sodium channels to stabilise neuronal membranes and inhibit transmitter release, principally glutamate. The role of glutamate in the aetiology of epilepsy is discussed.

Pharmacological studies on lamotrigine, a novel potential antiepileptic drug: I. Anticonvulsant profile in mice and rats

Lamotrigine (LTG), 3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine, is a structurally novel anticonvulsant. The anticonvulsant profile of LTG following oral administration in two standard anticonvulsant tests, the maximal electroshock (MES) test in mice and rats and the pentylenetetrazol (PTZ) infusion test in mice, was studied in comparison with the known anticonvulsant drugs phenytoin (PHT), phenobarbitone, diazepam, carbamazepine (CBZ), sodium valproate, ethosuximide (ETH), and troxidone (TROX). ED50 values for the abolition of hindlimb extension (HLE) in the MES test and PTZ infusion tests and doses increasing the latency of PTZ-evoked clonus were determined. The duration of action of LTG was examined in rats and mice in the MES test by determining ED50 values for the abolition of HLE at various drug intervals to shock administration. In the MES test, LTG was well absorbed in both species, with peak activity at 1 h and persistence at this level of potency for at least 8 h. Of the drugs examined, LTG was ranked the most potent and persistent in both species. LTG also abolished PTZ-evoked HLE, while ETH and TROX were inactive. Clonus latency was not increased by LTG, PHT, or CBZ, but was significantly increased (p less than 0.05) by the remaining anticonvulsants. Thus, LTG resembled PHT and CBZ in its ability to block HLE but not to increase PTZ-induced clonus latency. Acute behavioural studies in mice and rats have suggested a wide separation between anticonvulsant doses and those producing behavioural impairment. These results suggest that LTG may be of value in the treatment of generalised tonic-clonic and partial seizures.

Acute effects of lamotrigine (BW430C) in persons with epilepsy

Sixteen epileptic patients took single doses of lamotrigine, 120 mg or 240 mg. Six photosensitive patients showed reduction (with abolition in two) in photosensitivity after lamotrigine administration. Five subjects with frequent interictal spikes showed reduction in spike frequency over 24 h after lamotrigine administration. The half-life (t1/2) of lamotrigine in subjects taking sodium valproate was prolonged, whereas the t1/2 in subjects taking carbamazepine and/or phenytoin was reduced. The area under the curve of co-medication plasma levels was not affected by a single dose of lamotrigine. Five patients reported mild and generally transitory side effects; some of which represented exacerbation of preexisting complaints.

Lamotrigine (BW430C), a potential anticonvulsant. Effects on the central nervous system in comparison with phenytoin and diazepam

Twelve healthy male volunteers received phenytoin 0.5 and 1 g, lamotrigine (a new anticonvulsant) 120 and 240 mg, diazepam 10 mg and placebo orally in a double-blind, cross-over, randomized trial. Maximum drug concentrations at 4 h, measured in plasma were 11.5 +/- 2.2 micrograms ml-1 for phenytoin and 2.7 +/- 0.4 micrograms ml-1 for lamotrigine. These levels were in the therapeutic range for phenytoin and the putative therapeutic range for lamotrigine. Side effects after diazepam (mainly sedation) and phenytoin (mainly unsteadiness) differed markedly from lamotrigine which produced no important side effects. Subjective effects as measured by visual analogue scales were caused by phenytoin and diazepam but not by lamotrigine. Diazepam impaired eye movements, adaptive tracking and body sway. Phenytoin impaired adaptive tracking, increased body sway and impaired smooth pursuit eye movement. Lamotrigine produced only a possible slight increase in body sway. There were significant correlations between performance and saliva levels of phenytoin and diazepam. It was concluded that the tests used were suitable for monitoring CNS effects of anticonvulsants and that lamotrigine possibly could have a more favourable CNS side effect profile than phenytoin.

Changes in cortical amino acids during electrical kindling in rats

The effect of kindling rats by electrical stimulation of the frontal cortex for approx. 3 months on the concentrations of amino acids (taurine, aspartate, glutamate, glutamine and GABA) in the cerebral cortex has been studied, as well as the release of endogenous amino acids from kindled slices of brain in vitro. In these kindled rats, killed 1 week after the last shock, there were no changes in any concentrations of amino acids. However, when cortical slices, prepared from either the control or kindled rats, were stimulated in vitro by exposure to veratrine, more endogenous glutamate and aspartate were released from the kindled tissue than from the control. The neurotransmitter amino acids, glutamate and aspartate, may be involved in the permanent effects of electrical kindling.

[High-dose cytarabine treatment in acute leukemias and leukemic meningiosis: clinical aspects and pharmacokinetics]

Clinical reports concerning the therapeutic effects of high dose Cytosine arabinoside (HD Ara-C) in meningeal leukemia are relatively rare. Pharmacokinetic studies, however, have indicated potentially effective concentrations of Ara-C in cerebrospinal fluid (CSF) during and after high-dose infusions of the drug given intravenously. In this report, the treatment results of HD Ara-C in 14 patients with refractory or relapsed acute leukemia are presented including those of 2 patients with meningeal leukemia. In these 2 patients as well as in 1 patient without central nervous system (CNS) leukemia, Ara-C and Ara-U concentrations in CSF and plasma were measured during a 6-day therapy with HD Ara-C (3 g/m2 q 12h 12 X). Ara-C and Ara-U levels were determined on Days 3 and 6 of therapy, each at the end of a 3-h i.v. infusion of the drug. In the 14 patients (8 with AML, 6 with ALL) treated, a total number of 17 treatment cycles were given for remission induction with doses of Ara-C ranging from 1-3 g/m2 q 12 h 6-12 X. A complete remission rate of 47% was achieved. The duration of remission ranged from 1 to 6 months. Of the 2 patients with CNS leukemia, 1 patient achieved complete remission both in CSF and in bone marrow, the other patient only in CSF. The mean concentration of Ara-C in CSF was 903 ng/ml with a ratio of 0.38 to that in plasma. Ara-C and Ara-U did not appear to accumulate in CSF or in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)