Submandibular salivary gland transfer for the prevention of radiation-induced xerostomia in patients with nasopharyngeal carcinoma: 5-Year outcomes

BACKGROUND

Our aim in this study was to investigate the value of the submandibular salivary gland transfer procedure in prevention of radiation-induced xerostomia in patients with nasopharyngeal carcinoma (NPC).

METHODS

In all, there were 70 patients, consisting of a test group (36 patients) and a control group (34 patients) in a nonrandomized fashion. In the test group, the submandibular salivary gland was transferred to submental space before radiotherapy (XRT) and shielded. Salivary gland functions were evaluated by the amount of saliva and a quality of life questionnaire before and after XRT and 3 and 60 months after XRT.

RESULTS

At 5 years, the trapping and excretion functions of salivary gland were significantly better in the test group (p = .000 and p = .000). The mean weight of saliva after XRT was heavier (1.65 g vs 0.73 g, p = .000), and the incidence of xerostomia was lower in the test group, with no difference in 5-year survival and neck nodal recurrence between the 2 groups.

CONCLUSIONS

Salivary gland transfer procedure prevents XRT-induced xerostomia and improves quality of life of patients with NPC.

Reconstruction of soft-tissue defects of the head and neck: radial forearm flap or anterolateral thigh flap?

This study compared the reliability, practicability and impact to donor site functionality of radial forearm (RF) and anterolateral thigh (ALT) flaps used for the reconstruction of head and neck soft-tissue defects. The clinical data of patients who underwent reconstruction using RF flaps (n = 53) and ALT flaps (n = 21) after tumour ablation were reviewed. Pedicle length, skin area harvested and flap survival rate were compared between the two flap types. A questionnaire was used to compare the patients' perceptions of donor site functionality. Pedicle length did not significantly differ between RF and ALT flaps (7.5 vs. 9 cm, p = 0.733). A significantly larger mean area of skin was harvested in the ALT group than in the RF group (65 vs. 38 cm(2), p = 0.001). Flap survival rates did not differ between the two groups (p = 0.554). Patients in the ALT group were more satisfied with the appearance of the donor sites than were those in the RF group (p = 0.029). Significantly more patients in the RF group complained of donor site numbness than in the ALT group (p = 0.014). No ALT group patients complained of movement impairment or weakness at the donor sites, but 10% of RF group patients experienced impairment (p = 0.014) and 35% felt weakness (p = 0.001). The ALT and RF flaps showed similar practicability and reliability for the reconstruction of soft-tissue defects, but ALT flaps had fewer impacts to donor site functionality than RF flaps.

Laryngeal framework reconstruction using titanium mesh in glottic cancer after frontolateral vertical partial laryngectomy

OBJECTIVES

To investigate the feasibility and efficacy of laryngeal framework reconstruction using titanium mesh in patients with glottic cancer after frontolateral vertical partial laryngectomy.

STUDY DESIGN

Prospective study.

METHODS

Defect of laryngeal framework, caused by frontolateral vertical partial laryngectomy in nine patients with T2 or T3 squamous cell carcinoma of glottic, were reconstructed with titanium mesh from 2007 to 2009. Computed tomography (CT) and fiberscopic examinations were performed at two weeks and three months postoperatively.

RESULTS

No aspiration and laryngeal stenosis was observed in the nine patients. CT scanning showed that titanium mesh was fastened well without displacement and deformity and that there was no laryngeal stenosis. Fiberscopic inspection showed that the larynx lumen was maintained well without stricture, shrinkage, and necrosis. No titanium mesh was exposed to the larynx lumen.

CONCLUSIONS

Titanium mesh was a good alternative for reconstruction of the laryngeal framework. It provided adequate structural support to maintain airway patency.

[Application of anterolateral thigh free flap to reconstruct head and neck soft tissue defects]

BACKGROUND AND OBJECTIVE

Although anterolateral thigh (ALT) flap has the advantage of limited damage to the donor site, its clinical application is not common. This study was to study the clinical value of ALT flap in the reconstruction of head and neck soft tissue defects.

METHODS

Twenty patients receiving reconstruction of head and neck soft tissue defects using ALT flap at Sun Yat-sen University Cancer Center between November 2004 and May 2008 were retrospectively reviewed. Surgical procedures in the harvest of ALT flap were described. The surgical anatomy and successful rate were reported.

RESULTS

Twenty patients were all alive. The vessel pedicle length of ALT flap ranged from 5 cm to 14 cm, with an average of 9.9 cm. The harvested ALT flap was (4-9) cm X (6-16) cm. The skin perforator was classified into four cases of intermuscular septal branch (20%) and 16 cases of musculocutaneous branch (80%). The head and neck soft tissue defects included 14 cases (nine cases of tongue and oral floor, three cases of buccal mucosas, one case of hard palate, and one case of retromolar trigone mucosa) intraoral mucosa and six cases of facial-cervical skin defects. Except for one case, the donor sites were primarily sutured.

CONCLUSION

ALT flap is one of valuable and potential donor site for the reconstruction of head and neck soft tissue defects. It could achieve a high successful rate and causes little influence to the donor sites.

Expression and clinical significance of SPARC in clinical stage II tongue squamous cell carcinoma

BACKGROUND AND OBJECTIVE

Secreted protein acidic and rich in cysteine (SPARC) is expressed widely in malignant tumors. It is related to prognosis and biological behaviors of tumors. This study was to detect the expression of SPARC in stage II tongue squamous cell carcinoma and analyze its relationship with prognosis.

METHODS

Tongue carcinoma samples (T2N0M0) were obtained from 55 patients treated in Sun Yat-sen University Cancer Center from January 1999 to December 2003. Twenty-five squamous epithelium samples with tongue inflammation nearby were taken as control. Immunohistochemistry was used to detect the expression of SPARC. Its relationships with survival, occult lymph node metastasis and recurrence were analyzed.

RESULTS

The positive rate of SPARC was 49.1% in tongue cancer tissues and 0 in normal tissues (p < 0.001). The accumulative 5-year survival rate was significantly lower in SPARC-positive patients than in SPARC-negative patients (30.0% vs. 85.3%, p = 0.005). The positive rate of SPARC was significantly higher in tissues with occult lymph node metastasis than in those without metastasis (86.7% vs. 35.0%, p = 0.001), and higher in tissues with recurrence than in those without recurrence (100% vs. 31.5%, p < 0.001). The expression of SPARC was positively correlated to occult lymph node metastasis (r = 0.46, p < 0.001) and recurrence (r < 0.595, p < 0.001).

CONCLUSION

SPARC is highly expressed in stage II tongue squamous cell carcinoma, and positively correlated to survival, occult lymph node metastasis and recurrence.

[Correlation of cervical lymphatic metastasis to prognosis of T3-T4 glottic cancer]

BACKGROUND & OBJECTIVE

The cervical lymphatic metastasis rate of glottic cancer is low, and has seldom been reported. This study was to explore the factors related to cervical lymphatic metastasis of T3-T4 glottic cancer, and analyze its correlation to prognosis.

METHODS

Clinical data of 83 patients with T3-T4 glottic cancer, treated in Cancer Center of Sun Yat-sen University from 1992 to 2000, were reviewed retrospectively. The lymphatic metastasis rate, distribution of metastatic lymph nodes, influence factors of neck recurrence of cN0 glottic cancer, and correlation of cervical lymphatic metastasis to prognosis of T3-T4 glottic cancer were analyzed.

RESULTS

Overall lymphatic metastasis rate was 20.5%. The neck recurrence rate of cN0 patients was 14.3%. Most metastatic lymph nodes located at the ipsilateral levels II, III, and IV, while only 1 located at the contralateral level II. For cN0 patients, there was no difference in the neck recurrence rate between observation group and prophylactic cervical radiation group (P=0.772). Histopathologic differentiation affected the neck recurrence of cN0 patients (P=0.028); while T stage did not relate to the neck recurrence (P=0.217). The prognosis of cN+ patients was poorer than that of cN0 patients (P<0.001). The neck recurrence of CN0 patients did not affect the prognosis (P=0.460).

CONCLUSION

Most metastatic lymph nodes of T3-T4 glottic cancer locate at the ipsilateral levels II, III, and IV. Poor differentiation is significantly correlated to high risk of neck recurrence among cN0 patients. However, the recurrence does not affect the prognosis. Close observation should be done to the cervix of cN0 patients; while neck dissection should be done to cN+ patients.

Genetic diversity and variation of saponin contents in Panax notoginseng roots from a single farm

Radix notoginseng, the root of Panax notoginseng (Burk.) F. H. Chen, has been widely used in traditional Chinese medicine. Its main components, saponins, have been reported to have many pharmacological activities. To test the general assumption that herbs of a single species planted and harvested from a single location are uniform in chemical and genetic makeup, chemical analysis and DNA fingerprinting were carried out. High-performance TLC together with HPLC analysis were used to analyze 17 randomly sampled 3-year-old roots from a single farm for the presence of six saponins. Five roots showed distinct chemical profiles with changed ratios of ginsenosides Rd/Rg1, Re/Rg1, or Rb1/Rg1. The same samples, together with some 1- and 2-year-old samples, were also subjected to fluorescent amplified fragment length polymorphism (AFLP) analysis, and their internal transcribed spacer 2 (ITS 2) regions were sequenced. Fluorescent AFLP analysis was found to be much more polymorphic than the ITS 2 sequence and showed clear evidence of genetic diversity within the tested population. In conclusion, genetic diversity and variation of saponin contents between individual P. notoginseng roots have been detected. We suggest that genetic diversity affects the contents of the six saponins. The saponin contents variation and genetic diversity were also found among P. notoginseng root samples collected from China and Singapore markets. Since variable saponin contents may affect therapeutic efficacy, combining the use of genetic profiling with chemical profiling will help ensure greater uniformity in the quality of P. notoginseng roots. The genetic and chemical diversity within a population also provides the opportunity for breeding new cultivars with more desirable chemical constituents.

[Primary effect of submandibular salivary gland transfer in preventing radiation-induced xerostomia of nasopharyngeal carcinoma]

BACKGROUND & OBJECTIVE

Xerostomia, an ubiquitous sequelae in nasopharyngeal carcinoma (NPC) patients after radiotherapy, seriously affects life quality of the patients. This study was to investigate clinical value of submandibular salivary gland transfer in preventing radiation-induced xerostomia of NPC patients.

METHODS

A total of 70 eligible patients with NPC were recruited, and divided into test group (36 patients) and control group (34 patients). In test group, the submandibular glands were transferred to the submental spaces before conventional radiotherapy. The submental spaces were shielded during radiotherapy. Oral cavity mucous membrane reaction during radiotherapy, submandibular gland function and salivary fluid before and after radiotherapy, and questionnaire of xerostomia 3 months after radiotherapy were compared between test group and control group.

RESULTS

Acute oral cavity mucous membrane reaction was severer in control group than in test group; the incidence of stage III reaction was significantly higher in control group than in test group ( 8/34 vs. 3/36, P = 0.007). Three months after radiotherapy, trapping and excretion functions of the transferred submandibular glands were significantly better than those of the untransferred submandibular glands in test group (P = 0.001 and P = 0.000); trapping and excretion functions of the submandibular glands were significantly better in test group than in control group (P = 0.004 and P = 0.000). The mean weight of salivary fluid after radiotherapy was heavier in test group than in control group (1.41 g vs. 0.71 g). Incidence of moderate to severe degree of xerostomia was significantly higher in test group than in control group (76.5% vs. 13.9%, P = 0.000).

CONCLUSION

Submandibular gland transfer may be used to prevent radiation-induced xerostomia of NPC patients, and may improve life quality of the patients.

[Clinical analysis of xerostomia in patients with nasopharyngeal carcinoma after radiation therapy]

BACKGROUND & OBJECTIVE

There is few report on the xerostomia of the patients with nasopharyngeal carcinoma after conventional radiation therapy. Xerostomia is a serious, permanent, and ubiquitous sequelae in the patients with nasopharyngeal carcinoma after conventional radiation therapy. It has a significant impact on the patient's quality of life. This study was designed to investigate the severity of xerostomia and its impact on the quality of life in patients with nasopharyngeal carcinoma after conventional radiation therapy.

METHODS

One hundred and thirty-six patients with nasopharyngeal carcinoma, treated by conventional radiation therapy in Cancer Center, Sun Yat-sen University, were surveyed by interview at the outpatient. A questionnaire and a visual analog scale (VAS) were used in analysis of xerostomia and xerostomia-related problems.

RESULTS

Of 136 patents, 73.5% of the patients experienced a moderate to severe degree of xerostomia. 82.4% of the patients had to sip water to facilitate speech; 92.6% of the patients had to sip water to facilitate chewing and swallowing; 91.2% of the patients changed their feeding pattern (can eat only mashed food); 61.3% of the patients had to wake up to drink water because of dry mouth; 75.0% of the patients had teeth deteriorated.

CONCLUSION

73.5% of the patients with nasopharyngeal carcinoma after conventional radiation therapy experienced a moderate to severe degree of xerostomia. Xerostomia has a significant impact on the patient's speech, deglutition, sleep, and increases the morbidity rate of the tooth.

[Effectiveness evaluation and prognostic factor analysis in patients with minor salivary gland carcinoma of the hard palate]

BACKGROUND & OBJECTIVE

Minor salivary gland carcinoma of the hard palate is rare, and its long-term survival rate is high, making it difficult to evaluate the prognostic factors and the efficacy of treatment. This study was designed to evaluate the efficacy of treatment and investigate the prognostic factors of minor salivary gland carcinoma of the hard palate.

METHODS

Ninety-six cases of minor salivary gland carcinoma of the hard palate hospitalized in Cancer Center, Sun Yat-sen University, from 1964 to 2001 were reviewed retrospectively. The cumulative survival rate was analyzed by Kaplan-Meier method. The factors were compared using the log-rank test. The influencing factors were screened by Cox proportional hazards model.

RESULTS

The 5- and 10-year overall survival rates were 65.60% and 47.90%, respectively. The 5- and 10-year disease-specific survival rates for the patients treated with surgery (53 cases) and surgery + radiotherapy (35 cases) were 73.14%, 67.40% and 66.58%,46.60%,respectively. Multivariate analysis showed that age >or=50 years old,tumor size >or=3 cm,surgical margin status,and recurrence were independently associated with decreased survival rates (P< 0.05).

CONCLUSION

Surgery or surgery dominated multi-modality therapy was the principal treatment modality for minor salivary gland carcinoma of the hard palate. Age >or=50 years old, tumor size >or=3 cm, surgical margin status, and recurrence are independent factors affecting the prognosis.

The biological behaviour of human adenoid cystic carcinoma cells transduced with interleukin-2-gene

Adenoid cystic carcinoma (ACC) of the salivary glands is a highly infiltrative malignant tumour with a tendency for lung metastasis. Gene therapy could be a potentially effective therapy for ACC and its metastasis. The aims of the study were: To transduce interleukin-2 (IL-2) gene into an ACC cell line with predisposition for lung metastasis (ACC-M); to compare the bioactivity of the gene-transduced cells and the parent cell line in vitro and in vivo. The IL-2 gene was transduced via a bicistronic retroviral vector into the ACC-M cells. The growth rate and DNA cell cycles of the parent ACC-M, the control viral vector AmGCEN, and the gene transduced AmIL-2 cell cultures were compared quantitatively and by flow cytometry, respectively. The tumourigenic ability of the three cell lines was verified by inoculation in athymic nude mice. The tumours developed were extracted and compared quantitatively and histologically. There was no difference in the growth rate and the DNA count between the ACC-M, AmGCEN, and AmIL-2 cell cultures. In the animal experiment, both the ACC-M and AmGCEN cells stimulated lung metastasis in all the mice, whereas there was no tumour found in the 1 x 10(6) AmIL-2 cells inoculation. On 3 x 10(6) AmIL-2 cells stimulation, three out of six mice developed tumours but the mass and volume of the tumours were smaller than the other two groups. Under light microscopy, the ACC-M tumours were mainly poorly differentiated with minimal cellular matrix, whereas the AmIL-2 tumours were well differentiated with ample matrix. The transduction of IL-2 gene can reduce the tumourigenicity of ACC-M cells and induces tumour cell differentiation in mice. The IL-2 gene can be a potential effective gene for the treatment of adenoid cystic carcinoma of salivary glands and its lung metastasis.

[A study of the magnification of mandible pantomography image]

OBJECTIVE

To study the degree of magnification of mandible pantomography image.

METHODS

The pantomography of 50 mandible specimens marked with lead pellets were taken by TROPHY XL-90C. The distances between each markers on film and in specimen were measured.

RESULTS

The mean magnification(MM) of mandible pantomography image with TROPHY XL-90C was 1.22. MM of horizontal axle was 1.14. MM of vertical axle was 1.29. MM of horizontal axle was greatest (1.24) in the body of mandible,and lest (1.08) in genion. MM of vertical axle is similar among each regions. MM of vertical axle was greater than that of horizontal axle in all regions.

CONCLUSION

The MM parameters of mandible pantomography image were useful to estimate the size of mandible lesions and provided a basis for dental implant more exactly.

Drug-induced QT prolongation in women during the menstrual cycle

CONTEXT

Women have a higher incidence of torsades de pointes than men, but it is not known if the risk of drug-induced torsades de pointes varies during the menstrual cycle.

OBJECTIVES

To determine if the degree of QT prolongation in response to ibutilide varies with the menstrual cycle phase and to compare QT prolongation between women and men.

DESIGN AND SETTING

Cohort study of men and women who received the same intervention conducted between November 1998 and November 2000 at a general clinical research center of a university hospital.

PARTICIPANTS

A volunteer sample of 58 healthy adults (38 men and 20 women) aged 21 to 40 years.

INTERVENTION

A low dose of ibutilide (0.003 mg/kg), infused intravenously for 10 minutes. Subjects were monitored for 120 minutes. Women received the intervention on 3 separate occasions to correspond with menstrual cycle phases, which were verified by using hormonal assays.

MAIN OUTCOME MEASURE

QT interval, recorded from electrocardiogram at timed intervals during and after ibutilide infusion and standardized for variations in heart rate (QTc).

RESULTS

Maximum (mean [SD]) millisecond increase in QTc after ibutilide infusion was greater for women during menses (63 [13]) and the ovulatory phase (59 [17]) compared with women during the luteal phase (53 [14]) and compared with men (46 [16]; P =.002 vs menses and P =.007 vs ovulation). Progesterone (r = -0.40) and progesterone-to-estradiol ratio (r = -0.41), but not estradiol (r = 0.14) or testosterone (r = 0.09), were inversely correlated with ibutilide-induced QT prolongation.

CONCLUSIONS

Menstrual cycle and sex differences exist in QTc responses to ibutilide, with the greatest increase in QTc corresponding to the first half of the menstrual cycle.

[Ultramicrostructural observation on epithelial cell disdifferentiation in rat tongue carcinogenesis induced by 4NQO]

OBJECTIVE

To clarify epithelial cell ultramicrostructure changes in oral carcinogenesis.

METHODS

The epithelial cell ultramicrostructures in tongue carcinogenesis induced by 4-nitroquinoline-1-oxide (4NQO) were observed by transmission electron microscope.

RESULTS

With the progress of oral carcinogenesis, regular changes of epithelial cell were showed: decrease in tonofibril, keratohyaline granules, desmosome; and increase in mitochondria. The basement membrane was broken in some severe dysplasia (sDP) and was broken through by parts of cell processes in in situ carcinoma (ISC).

CONCLUSION

Oral carcinogenesis is a multistep process. Epithelial cell aberrant differentiation is showed by a decrease in the synthetic products of epithelium cell.

[Epidemiology of dental caries and periodontal diseases in middle school students in Suzhou City]

OBJECTIVE

To assess the prevalence of dental caries and periodontal diseases in middle school students at the ages of 11 to 13 and 15 to 17.

METHODS

Dental caries and periodontal diseases were assessed strictly by "national survey table of dental caries and periodontal diseases for school students".

RESULTS

The study group consisted of 20 581 students. The percentage of dental caries, DMFT and DMFS in students 11 to 13 years of age were 23.6%,0.40 and 0.54, respectively. The corresponding results were 29.76%, 0.64 and 0.87 for students 15 to 17 years of age, respectively. The percentage of gingivitis and dental calculus in students 11 to 13 years were 75.33% and 35.86%, respectively. The corresponding values in students 15 to 17 years of age were 73.1% and 44.91%, respectively. Female students have significantly few gingivitis and dental calculus than male students in both groups.

CONCLUSION

Compared with the students at the same ages in other cities, students in Suzhou city have low percentage of dental caries and periodontal diseases.

[Experimental study of abnormal cell proliferation and differentiation in rat tongue carcinogenesis induced by 4NQO]

OBJECTIVE

To clarify the phenotypic characteristics of abnormal cell proliferation and differentiation in oral carcinogenesis.

METHODS

The expressions of gp230, a marker of epithelium cell differentiation, and proliferating cell nuclear antigen (PCNA) in rat tongue carcinogenesis induced by 4-nitroquinoline-1-oxide (4NQO) were detected by LSAB immunohistochemical staining.

RESULTS

With the progress of oral carcinogenesis abnormal proliferation and differentiation patterns were indicated by reduced expression of gp230 and increased expression of PCNA.

CONCLUSION

Oral carcinogenesis is the result of mucosa epithelium cell aberrant proliferation and differentiation.

Effects of all-trans retinoic acid and interferon-gamma on expression of RAR beta gene in Tca8113 cells

OBJECTIVE

All-trans-retinoic acid (ATRA) and interferons (IFNs) have been proven to synergistically amplify growth inhibition and apoptosis in the tongue squamous carcinoma cell line (Tca8113). Nuclear retinoic acid receptor-beta (RAR beta) was the key gene that mediated retinoid activity for squamous carcinoma cells. In order to understand the mechanism of ATRA combined with IFN gamma inhibiting growth of Tca8113 cells, this investigation focused on RAR beta mRNA expression.

MATERIALS AND METHODS

In this experiment, RT-PCR method was used to analyze the RAR beta expression level, and viable cell count assay was carried out for growth inhibition studies.

RESULTS

All-trans-retinoic acid (1 microM) and IFN gamma (1000 u/mL) inhibited cell growth by 39.2% and 44.4%, respectively. Synergistic inhibition of cell proliferation by 86.7% was found under combined treatment. The combination of suboptimal concentrations of ATRA (0.1 microM) with IFN gamma (1000 u/mL) showed a much stronger additive inhibitory effect on cell proliferation. ATRA (1 microM) and IFN gamma (1000 u/mL) increased RAR beta expression to 4 times and 3 times, respectively. The expression of RAR beta increased 12 times after treatment with combined ATRA and IFN gamma treatment.

CONCLUSIONS

These observations indicated that the use of combined ATRA and IFN may lead to enhanced antitumor effects. These results also suggested that ATRA and IFN mediated upregulating expression of RAR beta may play an important role in synergistic inhibition of proliferation in Tca8113 cells.

Female gender is a risk factor for torsades de pointes in an in vitro animal model

Recent clinical observations indicate that female gender is associated with a higher risk of developing torsades de pointes (TdP) cardiac arrhythmia. In this study, we used the Langendorff technique in isolated perfused rabbit hearts and the whole-cell patch-clamp technique in ventricular myocytes to examine the gender difference in TdP incidence and gain insight into the underlying mechanisms. Isolated rabbit hearts were perfused by using the Langendorff technique. TdP was induced by abrupt changes of cycle length (deltaCL) in the presence of Tyrode's solution containing 1 mM 4-aminopyridine (4AP) and 50% reduced Mg2+ and K+ (low K/Mg). The effects of 1 mM 4AP on cardiac potassium currents were characterized by using the patch-clamp technique. Results demonstrated that (a) no significant gender difference was observed in the absolute QT interval before or after 4AP perfusion in the presence of low K/Mg; (b) 4AP caused marked QT prolongation in the ECG; (c) a significantly higher TdP incidence (nine of 12) was found in female hearts compared with male hearts (three of 12; p < 0.05); (d) 1 mM 4AP primarily inhibited Ito, although a slight inhibition of IKr also occurred in low-K/Mg Tyrode's solution. (e) No inhibition of IK1 was observed. (f) No gender difference was found in the potassium current block produced by 4AP. Female gender is associated with a higher incidence of TdP in an experimental isolated heart model and mechanisms subsequent to QT prolongation may contribute to such a gender difference.

Comparison of tegaserod (HTF 919) and its main human metabolite with cisapride and erythromycin on cardiac repolarization in the isolated rabbit heart

Tegaserod (HTF 919) is a new drug being developed for gastrointestinal motility disorders. Because other gastrointestinal prokinetic agents, such as cisapride and erythromycin, cause slowing of cardiac repolarization and have been implicated in the development of the potentially fatal ventricular arrhythmia, torsades de pointes, a study was initiated to determine whether tegaserod and its main human metabolite adversely influence cardiac repolarization. By using isolated Langendorff-perfused rabbit hearts, we show that QT intervals remain unchanged at concentrations of tegaserod from 0.5 to 10 microM. It was not until the tegaserod concentration was increased to 50 microM (roughly 500-5,000 times more concentrated than those typically found in human plasma after administration of recommended clinical dosages), that a small, but significant increase in the QT interval (12+/-4%; p < 0.05; n = 4) was observed. No significant changes in QT occurred in the presence of the tegaserod metabolite at any of the concentrations tested (0.5-50 microM). In contrast, cisapride caused QT lengthening at concentrations as low as 0.1 microM, with significant QT increases occurring when 5-50 microM cisapride was used (22+/-4% to >70%, respectively; p < 0.01; n = 4). Erythromycin also caused significant lengthening of QT intervals (11+/-2%; p < 0.001; n = 4), although 100 microM concentrations of this drug were required to achieve this effect. These results demonstrate that both cisapride and erythromycin can slow cardiac repolarization at therapeutic doses and that tegaserod's lack of QT prolongation at therapeutic doses suggests that it has the potential to be a safer alternative to cisapride as a gastrointestinal prokinetic agent.

Prolongation of QT interval in isolated feline hearts by antipsychotic drugs

Some antipsychotic drugs have been found to prolong the QT interval on electrocardiographic (ECG) recordings, a phenomenon which, when severe, may facilitate the occurrence of complex ventricular arrhythmias such as torsade de pointes. However, the effects of these drugs on the cardiac repolarization process have not been evaluated extensively. This study was designed to examine the potency of five antipsychotic drugs in lengthening the QT interval of the perfused feline heart: haloperidol, risperidone, sertindole, clozapine, and olanzapine. The hearts were infused with increasing concentrations of drugs (0.1-20 micromol/L) for 40-minute intervals at each concentration. ECG recordings were made, with signals amplified and data recorded on a strip chart recorder. Four representative beats from each set of three signal recordings were chosen for QT interval measurement. Our data indicated that all tested drugs prolonged the QT interval in a concentration-dependent manner (p < 0.01). Haloperidol and risperidone were significantly more potent than sertindole, clozapine, and olanzapine (p < 0.001). At a concentration of 0.5 micromol/L over a 40-minute infusion interval, haloperidol lengthened the interval by 26.2+/-0.7%, risperidone by 19.4+/-2.2%, and sertindole by 8.9+/-3.5% (p < 0.05 compared with baseline); clozapine and olanzapine were less potent. Although species differences may limit extrapolation of our findings to humans, the cardiac potassium channels of felines clearly resemble those of humans. This model may serve as the basis for further studies of drug-induced prolongation of the QT interval and precipitation of ventricular arrhythmias.