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Biomedical subjects

S H Sindrup

Publications and source records attributed to S H Sindrup.

At least 55 records · Page 3Linked to original sources
PubMed1992

The effect of quinidine on the analgesic effect of codeine.

We have studied the hypoalgesic effect of codeine (100 mg) after blocking the hepatic O-demethylation of codeine to morphine via the sparteine oxygenase (CYP2D6) by quinidine (200 mg). The study was performed in 16 extensive metabolizers of sparteine, using a double-blind, randomized, four-way, cross-over design. The treatments given at 3 h intervals during the four sessions were placebo/placebo, quinidine/placebo, placebo/codeine, and quinidine/codeine. We measured pinprick pain and pain tolerance thresholds to high energy argon laser stimuli before and 1, 2, and 3 h after codeine or placebo. After codeine and placebo, the peak plasma concentration of morphine was 6-62 (median 18) nmol.l-1. When quinidine pre-treatment was given, no morphine could be detected (less than 4 nmol.l-1) after codeine. The pin-prick pain thresholds were significantly increased after placebo/codeine, but not after quinidine/codeine compared with placebo/placebo. Both placebo/codeine and quinidine/codeine increased pain tolerance thresholds significantly. Quinidine/codeine and quinidine/placebo did not differ significantly for either pin-prick or tolerance pain thresholds. These results are compatible with local CYP2D6 mediated formation of morphine in the brain, not being blocked by quinidine. Alternatively, a hypoalgesic effect of quinidine might have confounded the results.

Adult↗
PubMed1992

Lack of effect of mianserin on the symptoms of diabetic neuropathy.

The effect of the non-tricyclic antidepressant mianserin on symptoms of diabetic neuropathy has been studied in 18 patients in a double-blind, cross-over study with imipramine as a positive control. The patients were treated with placebo, mianserin, and imipramine, each for two weeks, in randomized order, with 1-3 weeks between the treatments. The symptoms were assessed by observer and self-rating scales. Mianserin was given in the fixed dosage of 60 mg per day, whereas the dose of imipramine was adjusted to yield the optimal plasma concentration of imipramine plus desipramine of 400-600 nmol.l-1. The mianserin plus desmethylmianserin plasma concentration ranged from 85 to 850 nmol.l-1, with the highest concentration in a patient who was a poor metabolizer of both sparteine and mephenytoin. The symptoms of neuropathy were significantly reduced during imipramine treatment, although somewhat less than in earlier studies. In contrast, mianserin produced no change in symptoms in comparison with placebo. As there was no evidence that higher mianserin (plus metabolite) steady-state concentrations were associated with a more favourable effect, the negative outcome appeared not to be related to underdosing with mianserin. In contrast to drugs with documented effects on the symptoms of diabetic neuropathy, mianserin has a very weak or no inhibitory effect on 5-HT and noradrenaline reuptake and this may explain its poor clinical effect.

Adult↗
PubMed1992

The selective serotonin reuptake inhibitor citalopram relieves the symptoms of diabetic neuropathy.

The effect of the selective serotonin reuptake inhibitor citalopram on diabetic neuropathy symptoms was examined in a double-blind, placebo-controlled, crossover study for two 3-week periods. Citalopram was given as a fixed dose of 40 mg/day. Data from 15 patients could be included in the statistical analysis. Citalopram significantly relieved the symptoms of neuropathy as measured by both observer- and self-rating in comparison with placebo. The steady-state plasma concentration of citalopram was 10 to 890 nmol/L. There was no significant relationship between the plasma concentration of citalopram and the effect of treatment as measured by observer- or self-rating. Two of 17 patients, both receiving citalopram, left the study because of side effects (nausea and vomiting or gastric upset and diarrhea). Side-effect ratings were significantly higher during administration of citalopram than during administration of placebo, but citalopram was generally well tolerated. Compared with earlier results obtained with imipramine administered on the basis of plasma level monitoring, citalopram appeared to be less effective, but seemed to be better tolerated.

Adult↗
PubMed1992

The relationship between paroxetine and the sparteine oxidation polymorphism.

The relationship between the selective serotonin reuptake inhibitor paroxetine and the sparteine oxidation polymorphism was investigated in a combined single-dose (30 mg) and steady-state (30 mg/day for 2 weeks) study including a panel of nine extensive metabolizers and eight poor metabolizers of sparteine. The median area under the plasma concentration-time curve (AUC) after the first paroxetine dose was about seven times higher in poor metabolizers than in extensive metabolizers (3910 versus 550 nmol.hr/L), whereas at steady state the median AUCss tau interphenotype difference was only twofold (4410 versus 2550 nmol.hr/L). Plasma half-life and steady-state plasma concentration were significantly longer and higher, respectively, in poor metabolizers than in extensive metabolizers (41 versus 16 hours and 151 versus 81 nmol/L). Paroxetine pharmacokinetics were linear in poor metabolizers and nonlinear only in extensive metabolizers. Sparteine metabolic ratio (MR = 12 hour urinary ratio of sparteine/dehydrosparteine), increased during treatment with paroxetine in subjects who were extensive metabolizers, and after 14 days treatment two extensive metabolizers were phenotyped as poor metabolizers and the remaining extensive metabolizers were changed into extremely slow extensive metabolizers with sparteine MRs of 5.7 to 16.5. The inhibition of sparteine metabolism was rapidly reversed after cessation of paroxetine administration. In the poor metabolizers there were no significant changes in MRs during the study. It is concluded that paroxetine and sparteine metabolism cosegregates, but the interphenotype difference in metabolism was less prominent at steady state than after a single dose, presumably because of saturation of the sparteine oxygenase (CYP2D6) in subjects who were extensive metabolizers. Paroxetine is a potent inhibitor of sparteine oxidation by CYP2D6 in vivo.

Adult↗
PubMed1992

Pharmacokinetics of the selective serotonin reuptake inhibitor paroxetine: nonlinearity and relation to the sparteine oxidation polymorphism.

Steady-state plasma concentrations of paroxetine were studied at five or more paroxetine dose levels (10 to 70 mg/day) in each of 13 extensive metabolizers of sparteine and at three or four dose levels (10 to 40 mg/day) in each of three poor metabolizers of sparteine, all treated for diabetic neuropathy symptoms. On a dose of 30 mg/day there was a 25-fold variation in steady-state concentrations (25 to 670 nmol/L). The upper extreme of this variation was made up by the poor metabolizers of sparteine and the lower extreme by some fast extensive metabolizers. Further, within the extensive metabolizer group, steady-state levels showed a significant, positive correlation with sparteine metabolic ratio at all dose levels. On increasing doses, a disproportionate increase in plasma drug levels was observed in the majority of patients. In nearly all extensive metabolizers the concentration-dose data were best described by a pharmacokinetic model assuming elimination by at least two kinetically distinct processes, one a high-affinity saturable process and one a low-affinity linear process. Estimates of clearance at low drug levels of the high-affinity process showed a significant negative correlation with the sparteine metabolic ratio. Clearance of the low-affinity process was not related to the metabolic ratio and was of the same magnitude in extensive and poor metabolizers. The data thus confirmed that the metabolism of paroxetine and sparteine cosegregates and indicated that the enzyme responsible for a high-affinity saturable paroxetine elimination process is identical with CYP2D6, the source of the sparteine oxidation polymorphism.

Adult↗
PubMed1992

Plasma beta-endorphin is not affected by treatment with imipramine or paroxetine in patients with diabetic neuropathy symptoms.

To determine the possible role of endogenous opioid peptides in the action of imipramine and paroxetine in painful diabetic neuropathy, beta-endorphin concentrations in plasma were measured in 20 patients during a double-blind, placebo-controlled randomized three-way crossover trial. Despite a significant reduction in neuropathy symptoms during both imipramine and paroxetine treatment, the beta-endorphin level was unaltered throughout the study. The plasma concentration of beta-endorphin was not related to plasma drug concentrations. Thus, this study does not provide evidence of a role of endogenous opioid peptides in the mechanism of action of imipramine and paroxetine in painful diabetic neuropathy.

Adult↗
PubMed1991

Concentration-response relationship in paroxetine treatment of diabetic neuropathy symptoms: a patient-blinded dose-escalation study.

A single-blind dose-escalation study with the selective serotonin reuptake inhibitor paroxetine was conducted in 19 diabetic patients with neuropathy symptoms. The effect of treatment was evaluated by self-rating using visual analog scales. After an initial placebo period, paroxetine doses were increased from 10 mg/day in 10 mg steps, until the dose was 30-70 mg/day. In all except four patients, there was a marked relief of symptoms. Plasma concentrations of paroxetine above 300-400 nM were required to insure maximal relief in the majority of patients responding on paroxetine, but a considerable interindividual variation was observed (10-800 nM, median of 195 nM). The therapeutic effect appeared to increase gradually as the plasma concentration increased. The great interindividual variation in the pharmacokinetics of paroxetine was confirmed, but as the effect is maximal within approximately 1 week, and the drug is nontoxic, it may be clinically feasible simply to titrate the dose from 20 mg/day until the maximal effect is achieved. However, it is advised that titration to an effect, in diabetic neuropathy using doses above 50 mg/day, be undertaken with care as there is limited experience with doses above this level in any population. The beneficial effect of paroxetine appeared to be maintained unaltered during an additional 1 month open-label treatment on optimal paroxetine doses.

Adult↗
PubMed1990

Codeine increases pain thresholds to copper vapor laser stimuli in extensive but not poor metabolizers of sparteine.

The analgesic efficacy and kinetics of a single oral dose of 75 mg codeine was investigated in 12 extensive metabolizers and 12 poor metabolizers of sparteine in a double-blind, placebo-controlled crossover study. The cosegregation of the O-demethylation of codeine to morphine with the sparteine oxidation polymorphism was confirmed. Hence morphine could not be detected in the plasma of any of the poor metabolizers, whereas detectable morphine plasma levels were found in 10 of 12 extensive metabolizers. Pain thresholds to laser stimuli were determined before drug intake and 90, 150, and 210 minutes after drug intake. Codeine significantly increased the pricking pain thresholds in the extensive metabolizers (p less than 0.05), whereas there were no significant changes in the poor metabolizers. No change in pain thresholds occurred with placebo in any of the two phenotypes. In the extensive metabolizers there was a significant positive correlation between the increase in pain threshold and plasma concentration of codeine. The study supports the hypothesis that morphine formation is essential for achievement of analgesia during codeine treatment.

Administration, Oral↗
PubMed1990

Concentration-response relationship in imipramine treatment of diabetic neuropathy symptoms.

A single-blind imipramine dose titration study was conducted in 15 diabetic patients with neuropathy symptoms. The effect of treatment was evaluated by use of visual analog scales. Imipramine doses were individually adjusted until doses yielded plasma concentrations of imipramine plus desipramine that were well above 400 nmol/L or until all neuropathy symptoms had vanished. In all except one patient, there was marked relief of symptoms. In the responding patients (n = 14), much of the effect occurred at plasma levels of imipramine plus desipramine below 100 nmol/L, but a considerable interindividual variation was observed. Concentrations above 400 to 500 nmol/L were required to ensure maximal effect in all patients, and we did not find any indication of a decreased effect at high drug levels. The dose-dependent kinetics of imipramine was confirmed, and dose increments should therefore be carried out in small steps and preferably with monitoring of drug levels.

Adult↗
PubMed1990

Different short-term effect of protein and carbohydrate intake on TSH, growth hormone (GH), insulin, C-peptide, and glucagon in humans.

The effect of isocaloric (500 kcal) protein and carbohydrate ingestion was studied in a crossover study in nine healthy humans. Subjects were studied twice after overnight fasting, with an interval of 3 to 7 days. Blood was collected for 240 min after food ingestion. The initial reaction of growth hormone (GH) and thyroid stimulating hormone (TSH) to protein and carbohydrate was identical, with a reduction in both GH and TSH, and nadir occurring after 45-60 min and 120 min, respectively. During the next 120 min TSH returned to starting level after carbohydrate intake but was still reduced after protein intake (p less than 0.04). After both diets GH increased after the initial decline, the increase was greatest after protein intake and maximum was reached at 180 min (p less than 0.02). It has been reported that the 5'-deiodination of T4 is stimulated by insulin and inhibited by glucagon. The physiological increase in insulin after carbohydrate ingestion (p less than 0.05), and the physiological increase in glucagon after protein ingestion (p less than 0.05) was not associated with any changes in TT4, FT4, TT3, FT3, or rT3 that could indicate changes in the 5'-deiodinase activity.

Adult↗
PubMed1990

Nonlinear kinetics of imipramine in low and medium plasma level ranges.

Steady state plasma concentrations of imipramine and desipramine were studied at three to nine different imipramine dose levels in 17 extensive metabolizers of sparteine and at two dose levels in two poor metabolizers of sparteine, all treated for diabetic neuropathy symptoms. The imipramine doses were changed stepwise from doses yielding plasma concentrations of imipramine plus desipramine below 150 nM, up to doses yielding therapeutic drug levels of at least 300-500 nM. The imipramine doses required to achieve therapeutic drug levels was 20 or 25 mg/day in the two poor metabolizers and 50-350 mg/day in the extensive metabolizers. In the extensive metabolizers, the concentration/dose ratio increased for imipramine and desipramine with increasing dose. Dose adjustments based on a simple linear prediction from drug levels at initial dose (50 or 75 mg imipramine/day) thus would result in 0-130% (median, 20%) overestimates, most pronounced in patients with initial low steady state levels. The nonlinear kinetics of imipramine thus may be a significant clinical problem in patients treated for diabetic neuropathy symptoms.

Adult↗
PubMed1990

Clomipramine vs desipramine vs placebo in the treatment of diabetic neuropathy symptoms. A double-blind cross-over study.

1. The effect of clomipramine and desipramine on diabetic neuropathy symptoms was examined in a double-blind, randomised, placebo controlled, cross-over study for 2 + 2 + 2 weeks. Drug doses were adjusted according to the sparteine phenotype, i.e. extensive metabolisers were treated with 75 mg clomipramine day-1 and 200 mg desipramine day-1 whereas poor metabolisers were treated with 50 mg day-1 of both drugs. Nineteen patients completed the study. 2. Plasma concentration of clomipramine plus desmethylclomipramine was 70-510 nM in extensive metabolisers, vs 590 and 750 nM in two poor metabolisers. Desipramine levels were 130-910 nM, vs 860 and 880 nM. 3. Both clomipramine and desipramine significantly reduced the symptoms of neuropathy as measured by observer- and self rating in comparison with placebo. Clomipramine tended to be more efficacious than desipramine. Patients with a weak or absent response on clomipramine had lower plasma concentrations (clomipramine plus desmethyl-clomipramine less than 200 nM) than patients with a better response. For desipramine a relationship between plasma concentration and effect was not established. 4. Side effect ratings did not differ for clomipramine and desipramine and on both drugs three patients withdrew due to side effects. 5. Compared with earlier results obtained with imipramine dosed on the basis of plasma level monitoring, clomipramine and desipramine on fixed doses appeared less efficacious whereas the side effect profiles were the same. At least for clomipramine, appropriate dose adjustment on the basis of plasma level monitoring may increase the efficacy.

Adult↗
PubMed1990

Psoriasis and polyneuropathy. Three case histories.

Neurophysiological examination of 3 psoriasis patients with symptoms of polyneuropathy revealed varying degrees of both sensory and motor nerve affection and indicated nerve fibre loss as well as demyelination. Previous reports have suggested a connection between peripheral nerves and psoriasis.

Adult↗
PubMed1989

Imipramine treatment in diabetic neuropathy: relief of subjective symptoms without changes in peripheral and autonomic nerve function.

The effect of imipramine on symptomatic peripheral diabetic neuropathy in 9 patients was examined in a double-blind cross-over study against placebo. The dose of imipramine was adjusted to yield optimal plasma levels of imipramine plus desipramine of 300-750 nM. Imipramine had a clear beneificial effect on the symptoms of the neuropathy, whereas no changes in a range of neurophysiological measurement was detected. Despite some adverse effects, especially of an anticholinergic nature, the patients generally preferred imipramine to placebo.

Adult↗