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Biomedical subjects

D Dressler

Publications and source records attributed to D Dressler.

At least 55 records · Page 3Linked to original sources
PubMed2000

The sternocleidomastoid test: an in vivo assay to investigate botulinum toxin antibody formation in humans.

In a small number of patients treated with botulinum toxin (BT) antibody (Ab) formation occurs. BT Ab can be detected by the mouse protection assay (MPA) or by the mouse diaphragm assay (MDA). Both methods, however, have major drawbacks. We tested a method for detecting BT Ab which measures the BT-induced reduction in the electromyographic amplitude of the mean maximal voluntary activation (M-EMG) of the sternocleidomastoid muscle. The M-EMG reduction was compared in 17 patients with cervical dystonia and secondary BT therapy failure to the M-EMG reduction previously measured in controls. Values more than 2 SD below the mean of controls were considered abnormal. Six patients showed BT Ab on the MPA and MDA; all of these had abnormal M-EMG reductions. Eleven patients showed no BT Ab on MPA and MDA testing; in ten of these the M-EMG reduction was normal, and in one it was pathological, but MDA testing later changed to positive under continued BT therapy. The sternocleidomastoid test is easy to perform and produces quantitative results. Since its sensitivity and specificity are at least as good as those of the MDA and the MPA, it can replace them.

Adult↗
PubMed2000

Electromyographic evaluation of cervical dystonia for planning of botulinum toxin therapy.

The success of botulinum toxin (BT) injections for treatment of cervical dystonia depends on precise identification of dystonic muscles and on quantification of their dystonic involvement. Conventionally, this is attempted by clinical examination analysing the dystonic head position. In this presentation, a more systematic approach is sought by using an electromyography (EMG)-based evaluation procedure. In 10 consecutive patients with cervical dystonia not previously exposed to BT clinical examination, analysing the dystonic head position was performed to classify patients into four groups with similar dystonic head positions. Additionally, a 2-channel concentric needle EMG was used to measure the amplitudes of dystonic and maximal voluntary activities in sternocleidomastoid (SCM), splenius capitis (SC) and trapezius/semispinalis capitis (T/SS) muscles bilaterally. The ratio between both amplitudes, the dystonia ratio, was used to quantify dystonic muscle involvement. In all patients dystonia ratios could be calculated. In patients with similar head positions, EMG evaluation revealed different qualitative and quantitative dystonic involvement patterns. In six patients, there were discrepancies in identification of dystonic muscles between clinical examination and EMG evaluation. EMG evaluation excluded dystonic involvement in five patients. All excluded muscles were SCM. In one of these patients, additional T/SS involvement was detected by EMG evaluation. In one patient, SC involvement was revealed by EMG evaluation. All dystonic muscle involvement detected by EMG evaluation represented genuine dystonic muscle coactivation rather than compensatory muscle activity. The EMG evaluation presented allows quantitative and qualitative identification of dystonic muscle involvement which cannot be achieved by clinical examination. Both pieces of information may be helpful for optimization of BT therapy.

Botulinum Toxins↗
PubMed2000

Electromyographic quantification of the paralysing effect of botulinum toxin in the sternocleidomastoid muscle.

The effect of botulinum toxin (BT) upon the human body has so far been measured by using clinical scales monitoring its overall therapeutic effect upon the disorders treated. Clinical scales, however, usually lack sensitivity, are rarely validated and are integrating a number of uncontrollable parameters. After validation of the methodology in a group of 10 controls, we investigated the BT-induced amplitude reduction of the maximal voluntary electromyographic activity (M-EMG amplitude reduction) of the sternocleidomastoid muscle in a group of 34 patients with cervical dystonia undergoing regular BT therapy with Botox (Allergan, Irvine, Calif., USA; n = 16) or Dysport (Ipsen, Maidenhead, UK; n = 18). With Botox doses of 20 mouse units the M-EMG amplitude reduction was 80% (SD = 3.9%, n = 4), with 40 it was 84% (SD = 10.8%, n = 4), with 60 it was 85% (SD = 2.6%, n = 2) and with 80 it was 91% (SD = 5.8%, n = 6). With Dysport doses of 100 mouse units the M-EMG amplitude reduction was 70% (SD = 7.6%, n = 4), with 200 it was 85% (SD = 10.4%, n = 5), with 300 it was 83% (SD = 9.2%, n = 3), with 400 it was 78% (SD = 6.7%, n = 3) and with 500 it was 91% (SD = 5.8%, n = 5). The methodology presented can measure M-EMG amplitude reductions with a precision of about 10%. Dose-efficacy relationships can be used for dose optimisation, evaluation of BT therapy failure and comparison of different preparations and types of BT.

Botulinum Toxins, Type A↗
PubMed1999

Dose linearity after oral administration of tacrolimus 1-mg capsules at doses of 3, 7, and 10 mg.

Tacrolimus is an immunosuppressant drug used for the prophylaxis of organ rejection in patients who receive allogenic liver or kidney transplants. This study investigated the relationship between tacrolimus blood concentration-time profiles after 3-, 7-, and 10-mg single oral doses were given to 18 healthy, drug-free, nonsmoking, institutionalized male volunteers. The protocol used a single-dose, 3-period, 3-treatment, nonmasked, randomized-block, complete crossover design. The 90% CIs of the ratios of dose-adjusted, mean, log-transformed values of maximum blood concentration, area under the tacrolimus blood concentration-time curve (0 to the last measurable concentration; lower limit of quantitation = 0.5 ng/mL), and area under the blood concentration-time curve (0 to 0) fell within the range of 125%, indicating dose proportionality for these parameters under experimental conditions. Power to detect a 20% difference for the 3 doses tested was 82.2%, 66.7%, and 72.8%, respectively.

Adult↗
PubMed1999

Effects of rifampin on tacrolimus pharmacokinetics in healthy volunteers.

Tacrolimus is a marketed immunosuppressant used in liver and kidney transplantation. It is subject to extensive metabolism by CYP3A4 and is a substrate for P-glycoprotein-mediated transport. A pharmacokinetic interaction with rifampin, an antituberculosis agent and potent inducer of CYP3A4 and P-glycoprotein, and tacrolimus was evaluated in six healthy male volunteers. Tacrolimus was administered at doses of 0.1 mg/kg orally and 0.025 mg/kg/4 hours intravenously. The pharmacokinetics of tacrolimus were obtained from serial blood samples collected over 96 hours, after single oral and intravenous administration prior to and during an 18-day concomitant rifampin dosing phase. Coadministration of rifampin significantly increased tacrolimus clearance (36.0 +/- 8.1 ml/hr/kg vs. 52.8 +/- 9.6 ml/hr/kg; p = 0.03) and decreased tacrolimus bioavailability (14.4% +/- 5.7% vs. 7.0% +/- 2.7%; p = 0.03). Rifampin appears to induce both intestinal and hepatic metabolism of tacrolimus, most likely through induction of CYP3A and P-glycoprotein in the liver and small bowel.

Administration, Oral↗
PubMed1999

Bioequivalence of 1 and 5 mg tacrolimus capsules using a replicate study design.

Tacrolimus (FK506, Prograf) is marketed for the prophylaxis of organ rejection following allogenic liver or kidney transplantation. A previously conducted, randomized, 24-subject, crossover bioavailability study of 1 and 5 mg capsules (one period each) failed to demonstrate bioequivalence. A single-dose, four-period, four-sequence, randomized, crossover, replicate study (N = 32) was therefore used to evaluate the bioequivalence of the marketed 1 and 5 mg capsules in healthy volunteers. Tacrolimus blood concentrations were measured serially over 72 hours using a commercially available ELISA assay. Noncompartmental pharmacokinetic parameters were determined. Ninety percent CIs of log-transformed parameter ratios were 90.5-101.9, 87.1-101.7, and 89.7-103.8 for Cmax, AUC0-t, and AUC0-infinity, respectively. Since all values were within 80% to 125%, the capsules are bioequivalent. Based on %CVs, intersubject variability was approximately two to three times greater than intrasubject variability. The safety of single 5 mg oral tacrolimus doses administered to healthy volunteers at 7-day intervals was also ascertained.

Abdominal Pain↗
PubMed1998

Higher prevalence of obsessive-compulsive symptoms in patients with blepharospasm than in patients with hemifacial spasm.

OBJECTIVE: The prevalences of obsessive-compulsive symptoms in patients suffering from blepharospasm and in those with hemifacial spasm were determined. The two conditions have similar symptoms, but only blepharospasm is etiologically linked to basal ganglia dysfunction. METHOD: After being interviewed with the Structured Clinical Interview for DSM-III-R, 13 patients with blepharospasm and 13 with hemifacial spasm completed the SCL-90-R and the Hamburg Obsession/Compulsion Inventory-Short Form. RESULTS: Patients in the blepharospasm group had significantly more obsessive-compulsive symptoms, as indicated by higher scores on the Hamburg Obsession/Compulsion Inventory-Short Form, than the patients with hemifacial spasm. SCL-90-R scores were in the normal range for nine and eight categories, respectively (out of nine). CONCLUSIONS: The findings provide additional support for the hypothesis that obsessive-compulsive symptoms are related to basal ganglia dysfunction.

Aged↗
PubMed1997

Severe tardive dystonia: treatment with continuous intrathecal baclofen administration.

Treatment of tardive dystonia with oral baclofen produces ambivalent and overall disappointing results. However, because only a small proportion of the baclofen penetrates into the central nervous system when administered orally, we tested whether it is possible to increase the efficacy of treatment by continuous intrathecal infusion of baclofen (CITB) in a patient with severe tardive axial dystonia unresponsive to conventional therapy. A dose of 100 micrograms/day improved muscle tone, head control, posture, and walking distance; electromyography showed a marked decrease of dystonic muscle activity with fully preserved voluntary muscle activity, and the patient reported substantial reduction of pain. Apart from some minor discomfort at the site of operation, no side effects were noted. Further studies should be encouraged to evaluate the usefulness of CITB for other patients with severe and otherwise untreatable tardive dystonia.

Antipsychotic Agents↗
PubMed1997

Spasmodic laryngeal dyspnea: a rare manifestation of laryngeal dystonia.

We describe clinical experiences in the management of three patients with laryngopharyngeal dystonia causing severe breathing problems. In contrast to spasmodic dysphonia, which presents with action-induced involuntary spasm of laryngeal muscles during speaking, all three patients showed laryngopharyngeal spasms primarily during respiration. In analogy to spasmodic dysphonia we propose the term spasmodic laryngeal dyspnea for this rare condition. Localized unilateral botulinum toxin injected into the thyroarytenoid muscle and/or ventricular folds reduced the quantity and quality of spasms and led to a pronounced improvement of breathing problems.

Aged↗
PubMed1997

Tacrolimus oral bioavailability doubles with coadministration of ketoconazole.

OBJECTIVE: To quantitate the effect of ketoconazole, an azole antifungal agent and potent inhibitor of CYP3A4 and P-glycoprotein, on the bioavailability of tacrolimus, a substrate of the CYP3A system and of P-glycoprotein. SUBJECTS AND METHODS: The pharmacokinetics of tacrolimus were studied in six healthy volunteers (two women and four men) in a four-dose study after each received single doses of tacrolimus alone (0.1 mg/kg orally and 0.025 mg/kg intravenously) and with coadministered ketoconazole (200 mg orally at bedtime for 12 days). The dose of tacrolimus was reduced during the ketoconazole phase (0.04 mg/kg orally; 0.01 mg/kg intravenously). Ketoconazole and tacrolimus doses were separated by approximately 10 hours. Whole blood tacrolimus concentrations were determined by enzyme-linked immunosorbent assay. Estimated pharmacokinetic parameters in whole blood (mean +/- SD) before and with ketoconazole were calculated with noncompartmental techniques. RESULTS: Coadministration of ketoconazole did not consistently affect tacrolimus clearance (55.6 +/- 16.7 ml/hr/kg versus 42.5 +/- 7.6 ml/hr/kg), and steady-state volume of distribution was unchanged (0.99 +/- 0.26 L/kg versus 0.93 +/- 0.25 L/kg). However, a significant increase in tacrolimus bioavailability (14% +/- 5% versus 30% +/- 8%; p < 0.01) was observed with coadministered ketoconazole. Hepatic bioavailability was unchanged by the presence of ketoconazole (96% +/- 1% versus 97% +/- 1%). CONCLUSIONS: Because ketoconazole did not alter hepatic bioavailability and because 10 hours separated administration times of the drugs, it appears that the marked increase in tacrolimus bioavailability can be explained by ketoconazole having a local inhibitory effect on tacrolimus gut metabolism or on intestinal P-glycoprotein activity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Rapid rate transcranial magnetic stimulation--a safety study.

We assessed the safety of repeated short trains (4 stimuli) of rapid-rate transcranial magnetic stimulation (rrTMS) over the left motor cortex in 6 healthy normal subjects. rrTMS involved two separate blocks of 50 consecutive trains of 4 stimuli at a frequency of 20 Hz and an intensity of 5-10% above active motor threshold. We monitored EEG, and assessed aspects of neurological (balance, gait, two-point discrimination, blood pressure, pulse rate), cognitive (attention, memory, executive function) and motor function (speed of movement initiation and execution and manual dexterity) before and after the two blocks of rrTMS. EMG was also recorded from a number of hand, forearm and arm muscles contralateral to the site of stimulation. Two blocks of repeated rrTMS at 20 Hz and 5-10% above active motor threshold did not produce any adverse effects. Measures of neurological, cognitive and motor function showed no change following rrTMS. From the EMG recording there was evidence of increase in the amplitude of the motor evoked potentials (MEPs) recorded from the biceps in one subject during the first block of rrTMS, but this did not occur in the second block. A similar magnification of MEPs was also observed in another subject only during the second block of stimulation. When applied using parameters falling within published guidelines (Pascual-Leone et al., 1993; Pascual-Leone et al., 1994), repeated rrTMS is a relatively safe technique in healthy normal subjects. As rrTMS allows disruption of cortical function for a longer period, it has the potential of becoming a particularly useful tool for the study of cognitive function as well as sensory or motor function.

Adult↗