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Biomedical subjects

A C van Loenen

Publications and source records attributed to A C van Loenen.

At least 19 recordsLinked to original sources
PubMed2004

[Medicinal cannabis for diseases of the nervous system: no convincing evidence of effectiveness].

--In 1996, the Netherlands Health Council issued a negative recommendation regarding the use of medication on the basis of cannabis (marihuana). However, interest in medicinal cannabis has certainly not waned since. --The neurological diseases for which cannabis could presently be used therapeutically are: multiple sclerosis, chronic (neuropathic) pain and the syndrome of Gilles de la Tourette. --Since September 2003, the Dutch Ministry of Health, Welfare and Sport delivers medicinal cannabis to Dutch pharmacies, so that now for the first time, medicinal cannabis can be given to patients on a prescription basis within the framework of the Opium Law. The result of this is that doctors and patients now assume that this is a medication for which the efficacy and safety have been established. --The question arises whether new scientific data have become available since 1996 that provide scientific support for the current Governmental policy. --In a recent clinical trial that has aroused much discussion, patients with multiple sclerosis and problematic spasticity were treated with oral cannabis or a placebo. There was no significant effect of treatment on the primary outcome measure, i.e. objectively determined spasticity. Nevertheless, it was concluded that the mobility was improved and that the pain was subjectively decreased. --Until now, convincing scientific evidence that cannabinoids are effective in neurological conditions is still lacking. --However, it is also not possible to conclude definitely that cannabinoids are ineffective; still, this is no basis for official stimulation of their use.

Cannabis↗
PubMed2004

[Recognition and treatment of gamma hydroxybutyric acid poisoning].

The number of cases of gamma-hydroxybutyric acid (GHB) poisoning is increasing rapidly. The substance is becoming more and more popular as a party drug, while the users are often unaware of the potential dangers of GHB abuse. If a GHB overdose is treated properly and on time, the patient generally recovers completely within 6 hours. Preventing aspiration and the timely initiation of artificial respiration are particularly important.

Drug Overdose↗
PubMed2003

Toxicokinetics of nortriptyline and amitriptyline: two case reports.

Two cases are presented of intentional intoxications with the tricyclic antidepressants (TCAs) nortriptyline (NT) and amitriptyline (AT). The peak plasma concentrations were 2290 microg/L and 2900 microg/L, respectively. The active metabolites E-10-hydroxynortriptyline (EHNT) and Z-10-hydroxynortriptyline (ZHNT) profiles were quite different as monitored for 5 to 10 days after presumed drug intake. In conclusion, these cases illustrate that (1) metabolite formation and elimination after intake of an overdose dose of NT and AT are stereoselective, and (2) NT and EHNT toxicokinetics and toxicodynamics are quite different. It also shows that a patient with a severe TCA overdose can still survive if he or she receives appropriate and quick supportive care, even if the prognostic markers QRS time, coma grade, and serum TCA levels predict poor outcome.

Adult↗
PubMed2000

Amphotericin B colloidal dispersion (Amphocil) vs fluconazole for the prevention of fungal infections in neutropenic patients: data of a prematurely stopped clinical trial.

We conducted an open label, randomised clinical trial to compare amphotericin B colloidal dispersion (ABCD, Amphocil) 2 mg/kg/day intravenously with fluconazole 200 mg/day orally, for the prevention of fungal disease in neutropenic patients with haematological malignancies. In the event of unresolved fever after 4 days of empirical antibacterial therapy, patients in both treatment groups were to receive ABCD, 4 mg/kg/day. However, the study had to be stopped in an early phase, due to severe side-effects of ABCD. A total of 24 patients were enrolled, 12 patients were randomly assigned to receive prophylactic ABCD, which was administered for a mean of 13.9 days. Fluconazole prophylaxis was given to 12 patients for a mean of 21.2 days. Therapeutic ABCD, 4 mg/kg, was initiated in four patients because of suspected fungal infection, all of whom had initially received fluconazole. A high rate of infusion-related toxicity of ABCD was observed. Chills occurred in 15/16 ABCD recipients (94%), accompanied by a temperature rise of >/=2 degrees C in 4/16 patients and of >/=1 degrees C but <2 degrees C in 10/16 patients. Other ABCD-related adverse events were hypotension (4/16), nausea with vomiting (5/16), tachycardia (7/16), headache (3/16) and dyspnoea (3/16). For premedication patients received: antihistamines (12/16), hydrocortisone (9/16) and/or morphine (6/16). ABCD was discontinued in 8/16 patients (50%) due to side-effects, which ultimately dictated early termination of the study. We conclude that ABCD is not suitable for antifungal prophylaxis in neutropenic patients due to severe infusion-related side-effects. Subject numbers were too low for conclusions on variables of antifungal efficacy.

Adolescent↗
PubMed1999

Continuous infusion of lorazepam versus medazolam in patients in the intensive care unit: sedation with lorazepam is easier to manage and is more cost-effective.

OBJECTIVE: To evaluate the effectiveness of lorazepam and midazolam for long-term sedation of critically ill, mechanically ventilated patients. DESIGN: Double-blind, randomized, controlled study. SETTING: Medical intensive care unit in a university teaching hospital. PATIENTS: Sixty-four evaluable adult patients admitted to the intensive care department requiring mechanical ventilation for >3 days. INTERVENTIONS: Patients were randomized to receive blinded solutions of either lorazepam or midazolam by continuous infusion. The lowest dose that achieved an adequate sedation was infused. The maximum dose allowed for each drug was 60 mg/hr for midazolam and 4 mg/hr for lorazepam. Sedation was assessed initially and at least every 8 hrs thereafter on a seven-point scale if the sedation was adequate and every 2 hrs if it was not. MEASUREMENTS AND MAIN RESULTS: Measurements included the score on the sedation scale, the time between determination of the desired level of sedation and the achievement of that level, and plasma concentrations. It is significantly easier to reach a desired level of sedation with lorazepam than with midazolam. No difference in recovery was found in the 24 hrs after discontinuation of therapy. The fact that there are many factors influencing midazolam pharmacokinetics may explain the more difficult management of desired sedation levels. The equipotent dose of 10 mg of midazolam proved to be 0.7 mg of lorazepam in long-term sedation. The average cost for therapy with midazolam was approximately ten times more than that with lorazepam. CONCLUSIONS: Lorazepam is a useful alternative to midazolam for the long-term sedation of patients in the medical intensive care unit and provides easier management of the sedation level. Sedation with lorazepam offers a significant cost-savings.

Adult↗
PubMed1999

Fluconazole versus itraconazole for the prevention of fungal infections in haemato-oncology.

AIMS: To compare the efficacy of and tolerance to oral fluconazole and intraconazole in preventing fungal infection in neutropenic patients with haematological malignancies. PATIENTS: 213 consecutive, afebrile adult patients treated with or without autologous stem cell transplantation for haematological malignancies. METHODS: A randomised, double blind, single centre study. Patients were randomly assigned to receive fluconazole 50 mg or itraconazole 100 mg, both twice daily in identical capsules. An intention to treat analysis was performed on 202 patients, 101 in each group. RESULTS: Microbiologically documented systemic fungal infections occurred in four patients in each group. Clinical fungal infection was thought to be present in seven recipients of fluconazole and four of itraconazole. In all 202 patients, 29 proceeded to intravenous amphotericin (amphotericin B), 16 in the fluconazole group and 13 in the itraconazole group. Superficial fungal infection was seen only in three non-compliant patients in the fluconazole group. All these infections were oral. No major differences were noted in the isolates of fungi in mouth washes and fecal samples. Overall mortality was 8.9% (18 deaths; seven in the fluconazole group, 11 in the itraconazole group). Mortality from microbiologically and clinically documented fungal infection was 4.5% (nine deaths; three in the fluconazole group, six in the itraconazole group). Median time to suspected or proven fungal infection was 16 days in both groups. None of these comparisons reached statistical significance (p < 0.05). No major clinical toxicity was noted and compliance was excellent. CONCLUSIONS: In neutropenic patients treated for haematological malignancies with or without autologous stem cell transplantation, fluconazole and itraconazole in low doses result in a similar low frequency of fungal disease. Fluconazole may be the preferable drug because of the smaller number of capsules and lack of need for timing relative to meals.

Adult↗
PubMed1996

Citrate compared to low molecular weight heparin anticoagulation in chronic hemodialysis patients.

Citrate and nadroparin calcium, a low molecular weight heparin (LMWH), were compared in a randomized cross-over trial in 21 chronic hemodialysis patients regarding anticoagulation, calcium and magnesium kinetics, biocompatibility, dialysis efficiency, and aluminum contamination. Citrate was infused into the arterial line at a minimum rate of 0.68 mmol/min, combined with a calcium and magnesium-free dialysate and intravenous supplementation of calcium and magnesium at rates of 0.22 and 0.10 mmol/min, respectively. Seven patients with a dialysis session of six hours, received 2/3 of the nadroparin dose predialysis, and 1/3 after 2.5 hours (divided dose (DD) group). A single predialysis bolus injection of nadroparin was administered to eight patients not on coumarins [single dose (SD) group] and to six patients on coumarins [single dose + coumarins (SD + C) group], all with a dialysis session of four hours. Nineteen patients received a nadroparin dose of 200 ICU/kg. Two patients with a single dose, one of them on coumarins, received a dose of 150 ICU/kg because of a hematocrit < 0.30. With citrate systemic whole blood activated clotting time (ACT) remained unchanged, indicating efficient regional anticoagulation. After two hours of dialysis with nadroparin, systemic ACT increments, that is, the increase compared to predialysis, of the DD, SD, and SD + C groups were 8.8 +/- 1.5, 18.7 +/- 4.7, and 33.3 +/- 6.1 seconds, respectively (mean +/- SEM). Postdialysis ACT increments in these groups were 1.5 +/- 3.4, 17.7 +/- 6.8, and 30.3 +/- 8.0 seconds. Two hour increments of systemic activated partial thromboplastin time (APTT) of the DD, SD, and SD + C groups during nadroparin were 5.0 +/- 1.2, 15.1 +/- 2.7, and 32.2 +/- 5.5 seconds, respectively, and the corresponding postdialysis APTT increments were 2.9 +/- 1.4, 7.8 +/- 2.4, and 15.8 +/- 2.6 seconds. Two-hour anti-Xa increments of the DD, SD, and SD + C groups amounted to 0.34 +/- 0.07, 0.67 +/- 0.07, and 0.80 +/- 0.08 IU/ml. The respective postdialysis anti-Xa increments were 0.21 +/- 0.06, 0.58 +/- 0.06, and 0.71 +/- 0.08 IU/ml (All ACT, APTT and anti-Xa increments were significant; P < 0.05), except for the ACT increments and the postdialysis APTT increment of the DD group). These increments, together with unchanged prothrombin fragments 1 and 2 (PTF1 + 2), indicate systemic anticoagulation with nadroparin. The increments of serum calcium and magnesium during citrate were comparable to the increments observed with a dialysate containing 1.5 mmol/liter calcium and 0.75 mmol/liter magnesium used in combination with nadroparin. Ionized calcium increments during citrate were significant after the end of dialysis, while the dialysate containing 1.5 mmol/liter calcium induced significant increments during and postdialysis. No differences were observed between citrate and nadroparin regarding biocompatibility), (expressed as dialysis-induced leukopenia and thrombocytopenia), and dialysis efficiency [measured as dialyzer urea and creatinine clearance, normalized weekly whole body urea clearance (Kt/Vurea) and time averaged urea concentration (TACurea)]. The citrate solution, if sterilized in glass bottles, contained 2 to 3 micrograms aluminum per mmol citrate, the nadroparin solution 0.009 microgram per 1,000 ICU. Aluminum contamination of the citrate solution was prevented by sterilizing the solution in polypropylene bottles. In conclusion, citrate anticoagulation is regional and is indicated for hemodialysis patients with an active or recently active bleeding focus. However, the citrate solution should be sterilized in polypropylene containers to prevent aluminum contamination. LMWHs induce systemic anticoagulation during hemodialysis, and this effect is enhanced by concomitant coumarin use and mitigated by a divided LMWH dose regimen. For hemodialysis patients not at risk of bleeding, LMWHs provide a simple anticoagulation regimen.

Aluminum↗
PubMed1994

4-aminopyridine in the treatment of patients with multiple sclerosis. Long-term efficacy and safety.

OBJECTIVE: To study the long-term efficacy and safety of 4-aminopyridine in patients with multiple sclerosis. DESIGN: Case series, follow-up varying from 6 to 32 months. SETTING: University referral center. PATIENTS: Thirty-one patients with definite MS, 23 of them being exposed to long-term administration (6 to 32 months) of 4-aminopyridine, since they showed a favorable initial response to the drug. INTERVENTIONS: Long-term oral treatment with 4-aminopyridine in daily doses of up to 0.5 mg/kg of body weight. MAIN OUTCOME MEASURES: Neurologic functions and symptoms as reported by the patients; side effects. RESULTS: Twenty of 23 patients who showed a favorable initial response benefited from long-term administration. Ambulation and fatigue (each in 13 patients) and visual function (in five patients) were most frequently reported to be improved. Three major side effects did occur during a follow-up of 406 patient months: a generalized epileptic seizure in two patients and hepatitis in one. CONCLUSIONS: Although a substantial proportion of patients with multiple sclerosis seem to benefit from long-term administration of 4-aminopyridine, additional studies are needed to clarify the exact value of the drug.

4-Aminopyridine↗
PubMed1994

4-Aminopyridine is superior to 3,4-diaminopyridine in the treatment of patients with multiple sclerosis.

OBJECTIVE: To compare the efficacy and toxicity of 4-aminopyridine and 3,4-diaminopyridine in patients with multiple sclerosis. DESIGN: Intervention study with a before-after design and a randomized, double-blind, crossover design. SETTING: University referral center. PATIENTS: Twenty-four patients with definite multiple sclerosis who had been treated in a previous clinical trial with 4-aminopyridine. INTERVENTIONS: Nonresponders to treatment with 4-aminopyridine (14 patients) were treated with 3,4-diaminopyridine in a 4-week, open-label trial with doses up to 1.0 mg/kg of body weight (before-after design). Responders to treatment with 4-aminopyridine (10 patients) participated in a comparative study of 6 weeks' duration with 4-aminopyridine and 3,4-diaminopyridine according to a randomized, double-blind, double-crossover design. MAIN OUTCOME MEASURES: Neurophysiologic variables for nonresponders, neurologic functions and symptoms on a visual analogue scale for responders, and side effects for both groups. RESULTS: Toxicity profiles of 4-aminopyridine and 3,4-diaminopyridine were different, and systemic tolerability was reduced for 3,4-diaminopyridine. 4-Aminopyridine was more effective than 3,4-diaminopyridine, especially for ambulation, fatigue, and overall daily functioning. CONCLUSION: Our data suggest that, concerning both efficacy and side effects, 4-aminopyridine is superior to 3,4-diaminopyridine in the treatment of patients with multiple sclerosis.

4-Aminopyridine↗
PubMed1994

The effects of 4-aminopyridine on cognitive function in patients with multiple sclerosis: a pilot study.

4-Aminopyridine (4-AP) has a favorable effect on the disability of certain patients with MS. We investigated the effect of 4-AP on neuropsychological performance in 20 MS patients using a randomized, double-blind, placebo-controlled, crossover design. Although there was a trend for improved performance with 4-AP for two of the tests, we could not demonstrate significant effects of 4-AP on cognitive function.

4-Aminopyridine↗
PubMed1993

[Good results of treatment of reflex sympathetic dystrophy with a 50% dimethylsulfoxide cream].

In this open prospective study dimethyl sulfoxide (DMSO), a hydroxyl radical scavenger, was tested in a 50% concentration in a fatty cream base (cremor vaselini cetomacrogolis FNA) in a total of 37 patients suffering from reflex sympathetic dystrophy. Patients were selected according to an RSD screening protocol. They also received physiotherapy. Eligible patients presented with acute signs of RSD and needed to have a sensation of heat in the extremity, as well as at least two of the following symptoms: (distal) pain, redness, swelling, loss of function, hyperhidrosis or increased hair growth and/or nail growth. Endpoints were the clinical improvement of the patient together with the patient's assessment of the pain according to a Visual Analog Scale (VAS: 0-10; 0 = no pain, 10 = unbearable pain). Successful treatment was accomplished when the VAS was halved and clinical signs had improved. The results showed a significant improvement in VAS score from 5.3 (SD 2.9) to 0.9 (SD 1.3; p < 0.01) in a mean treatment time of 3.4 months (SD 1.9). Systemic side effects consisted of a sulfurous smell of the exhaled breath of 12 patients. Concerning local side effects a mild dry, scaling effect on the skin was seen.

Acute Disease↗
PubMed1993

4-Aminopyridine induces functional improvement in multiple sclerosis patients: a neurophysiological study.

This study reports on the neurophysiological measurements that were performed in the context of a randomized, double-blind, placebo-controlled, cross-over study with intravenously administered 4-aminopyridine (4-AP) in 70 patients with definite multiple sclerosis (MS). A beneficial effect of 4-AP was found for both visual evoked response and eye movement registration parameters. This study extends the experimental data obtained on animal nerve fibers, showing that 4-AP can improve impulse conduction in demyelinated nerve, to clinical data which indicate that 4-AP induces an objective improvement in the central nervous system function in MS-patients. It thereby also provides a theoretical basis for clinical efficacy of 4-AP in MS.

4-Aminopyridine↗
PubMed1992

The effect of schedule, protein binding and growth factors on the activity of suramin.

Suramin has been shown to have antiproliferative activity, either by blocking the binding of growth factors to their receptors or by inhibiting critical cellular enzymes. In 6 different cell lines from 5 tumour types (MCF-7, MCF-7/ADRR, PC3, HT-29, UM-SCC-11B and SW-1573/IR500), we studied the effect of scheduling of suramin, of FCS and of human serum albumin (HSA), of epidermal growth factor (EGF) and of the addition of growth factors in serum-free medium on the activity of suramin. The concentration of suramin which gave 50% growth inhibition (IC50) varied from 45 microM in SW-1573/IR500 to 153 microM in PC3 cells grown in medium supplemented with 5% FCS, after 6 days of continuous exposure. Exposure for more than 4 days did not enhance the sensitivity to suramin, except in PC3. At exposure to suramin for 1 day followed by 5 days recovery, high IC50 values (greater than 0.5 mM) were observed in MCF-7 cells. In medium with 1% and 0.5% FCS these values were 3 to 8 and 14 to 26 times lower respectively. Addition of HSA increased the IC50 in PC3 and MCF-7 cells. Suramin binding to protein was dependent on the concentration of protein and of suramin. Excess of EGF in medium with different FCS concentrations did not change the IC50 values of suramin in PC3 and MCF-7 cells. Addition of EGF, fibroblast growth factor or platelet-derived growth factor in PC3 cells cultured in serum-free medium did not increase the IC50 values. Suramin was active against these 6 cell lines at clinically achievable concentrations. This activity varied depending on the cell line, exposure time and suramin concentration. The most significant factor interfering with sensitivity to suramin was the amount of protein present in the culture medium.

Blood↗