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Biomedical subjects

A H Sun

Publications and source records attributed to A H Sun.

14 recordsLinked to original sources
PubMed1999

Corticosteroid pharmacokinetics in the inner ear fluids: an animal study followed by clinical application.

OBJECTIVE: Autoimmune disease (e.g., Cogan syndrome) and other inflammatory inner ear diseases may ravage the labyrinth if not treated aggressively with antiinflammatory medication. Corticosteroids are the mainstay of treatment, yet, partly because of the existence of the blood-labyrinthine barrier, the ideal drug, dose, and route of administration are currently unknown. STUDY DESIGN: In the present study, we established cochlear fluid pharmacokinetic profiles of hydrocortisone, methylprednisolone, and dexamethasone in the guinea pig following oral, intravenous, and topical (intratympanic) administration. High-performance liquid chromatography was used to determine the drug concentrations, and comparisons were made with simultaneous pharmacokinetic profiles from blood and cerebrospinal fluid. RESULTS: Our findings demonstrated a much higher penetration of all three drugs into the cochlear fluids following topical application as compared with systemic administration, with methylprednisolone showing the best profile. DISCUSSION: The results suggested that intratympanic administration of corticosteroids might be more efficacious while avoiding high blood levels and therefore the deleterious side effects of systemic use. CLINICAL APPLICATION: Thirty-seven patients with various inner ear disorders causing sensorineural hearing loss were subsequently treated using intratympanic corticosteroids, 20 with dexamethasone, and 17 with methlyprednisolone. Patients with immune-mediated hearing losses showed the best results, with notable improvement also seen in several cases of a "sudden deafness." No benefit was seen in patients with cochlear hydrops or those with sudden deterioration of a preexisting hearing loss. Three patients developed a transient otitis media related to the treatments, easily controlled with antibiotics. There were no cases of treatment-induced hearing loss and no permanent tympanic membrane perforations. CONCLUSIONS: Overall injection of intratympanic corticosteroids for the treatment of hearing loss in inner ear disorders appears to be both safe and highly effective for certain disorders. The concept of this technique is supported by animal experimental data. The findings from the present study warrant further clinical application and experimental investigation.

Administration, Oral↗
PubMed1996

Comparative perilymph permeability of cephalosporins and its significance in the treatment and prevention of suppurative labyrinthitis.

Cephalosporins are nonototoxic antibiotics that provide excellent coverage for almost all bacteria that can cause suppurative labyrinthitis. In this study we performed comparative perilymph permeability determinations of the three cephalosporins that we deemed to have the most clinical potential in these varied situations. Perilymph pharmacokinetic profiles were established for ceftazidime, cefuroxime, and cefotaxime and its metabolite desacetylcefotaxime in 36 guinea pigs by using the technique of high-performance liquid chromatography. At 1, 2, 3, 4, and 6 hours after intravenous administration of the three cephalosporins at a dose of 100 mg/kg of body weight, ceftazidime consistently exhibited the highest perilymph concentration. Desacetylcefotaxime showed the next highest capacity for penetration into perilymph. Keeping in mind that the choice of drug for the treatment of suppurative labyrinthitis should be based foremost on culture and sensitivity studies, we consider ceftazidime to be the first-line agent for treatment and prevention of both meningogenic labyrinthitis and labyrinthitis complicating acute or chronic otitis media.

Animals↗
PubMed1995

Cefuroxime: pharmacokinetics in cochlear perilymph, cerebrospinal fluid, and plasma.

Very little is known about the permeability of contemporary antibiotics through the blood:perilymph barrier. In this study, we measure the concentration of cefuroxime in perilymph, cerebrospinal fluid (CSF), and plasma in the guinea pig following intravenous administration by using the technique of high-performance liquid chromatography. The results of our study demonstrate a higher permeability of cefuroxime in perilymph than in CSF with a similar concentration profile over time in both fluids. This suggests that each of the two fluid compartments has its own drug barrier, with little or no free passage from CSF to perilymph. On the basis of these experimental findings, we feel that cefuroxime has considerable potential as an antibacterial agent for the treatment or prevention of bacterial labyrinthitis.

Animals↗
PubMed1995

Teratoma of the middle ear.

Teratomas are true tumours derived from ectoderm, mesoderm, and endoderm, which differentiate into identifiable tissues and organs. Teratomas of the temporal bone are exceedingly rare, but should be considered in the differential diagnosis of a temporal bone mass at birth or during childhood. We present a case of a temporal bone teratoma involving the middle ear, judge the imaging capabilities of computed tomography in the diagnosis, and review the literature.

Child↗
PubMed1993

[Classification and treatment of torsades de pointes (TdP): a report of 11 cases].

A clinical analysis of 11 cases with TdP was reported. These patients were divided into two groups: 9 cases with long QT syndrome and 2 with normal QT interval. All of the patients suffered from coronary heart disease with various concomitant ailments, such as pulmonary heart disease (1 case), atrioventricular block (5 cases with complete or type II second degree AV block), hypokalemia (7 cases). In one case the TdP was caused by aminodarone administration. The principle of treatment included removing the inducing causes, treating the primary diseases and interrupting TdP. All patients who had hypokalemia were treated with potassium chloride. 7 of 9 cases showed effective response to treatment with magnesium sulfate. The patients with long QT syndrome failed to respond with MgSO4. Severe bradycardia should be treated with isoprenaline. Only one patient had pacing therapy and another received electric conversion. According to our experience, for patients of TdP with long QT syndrome class Ia and III antiarrhythmic agents were contraindicated, but those with normal QT interval can take these drugs.

Aged↗
PubMed1992

Idiopathic sudden hearing loss and disturbance of iron metabolism. A clinical survey of 426 cases.

The role of disturbances of the iron metabolism (DIM) in idiopathic sudden hearing loss (ISHL) was investigated in 426 patients with ISHL who received iron therapy, anti-DIM medication, vitamins, and a combined regimen in a randomized study which was stratified by stages and groups. Low concentrations of haemoglobin, serum iron, serum ferritin, and red cell basic ferritin as well as abnormal circadian variations in the serum iron level were observed. The results were significantly better in patients receiving iron therapy than in those receiving anti-DIM medication, vitamins, and the combined regimen. Hearing improvement was achieved in 53.26% of the patients whose treatment started later than 3 months after the onset of the disease. The clinical association of DIM and ISHL is discussed.

Adult↗
PubMed1992

Sudden sensorineural hearing loss induced by experimental iron deficiency in rats.

The relation between iron deficiency (ID) and sudden sensorineural hearing loss (SSHL) was evaluated in the growing rats of three different experimental groups. Fourteen rats of 132 (10.61%) that were raised on a basic ID diet showed SSHL in varied extent, from moderate to profound. By contrast, none of 128 standard control and 126 anemic control rats that were fed with the final iron-supplemented diet showed any degree of SSHL. The main cochlear correlates of SSHL in ID rats were synchronous abnormalities of the iron-containing enzymatic activity in the whole cochlea, a significant reduction of spiral ganglion cells and a rapid involvement of stereocilia of the outer and inner hair cells. The results suggest that ID can play a major role in the pathogenesis of SSHL.

Acoustic Stimulation↗
PubMed1991

Red cell basic ferritin concentration in sensorineural hearing loss.

Red cell basic ferritin (RCBF) was measured in 62 healthy subjects with normal hearing and 224 patients with different kinds of sensorineural hearing loss, compared with serum ferritin, haemoglobin, serum iron and circadian variation in the serum iron levels. The results showed that the RCBF concentrations in most kinds of sensorineural hearing loss were significantly lower than those in normal hearing status. It is conceivable that the RCBF assay can be used to evaluate the adequacy of iron stores that are useful in times of urgent iron needs and to diagnose relative iron deficiency in those patients with some other normal laboratory assays related to iron metabolism.

Adolescent↗
PubMed1991

Noise-induced hearing loss in iron-deficient rats.

The role of iron deficiency in noise-induced hearing loss (NIHL) was evaluated in 64 rats of four different experimental groups. Iron-deficient rats (ID-rats) and normal rats (N-rats) were simultaneously exposed to a steady state white noise (20-10,000 Hz) at 110 dB SPL for 30 min. Unexposed ID- and N-rats served as controls. In N-rats the temporary threshold shifts (TTS) would have completely disappeared if the animals were allowed to survive for 72 h. No permanent threshold shift (PTS) was seen in any of the N-rats. The ultrastructural correlates in N-rats are stereocilia disarray and mitochondria swelling in outer hair cells (OHCs). The TTS in ID-rats were larger than those in the N-rats, and most ID-rats with larger threshold shifts showed varying degrees of PTSs at 11 days post-exposure. The ultrastructural correlates of NIHL in ID-rats are obvious pathology of the stereocilia, such as segmental coalescence of stereocilia of many continuous OHCs and fusion of the tips of stereocilia of OHCs, and a significant reduction of mitochondria as well as slight degeneration of nucleus in the OHCs. It is concluded that iron deficiency can provide a pathological basis for NIHL.

Anemia, Hypochromic↗
PubMed1990

Changes in the cochlear iron enzymes and adenosine triphosphatase in experimental iron deficiency.

The influences of iron deficiency on the cochlear iron enzymes and adenosine triphosphatase were studied in 68 iron-deficient rats and 68 control rats (normal and with chronic anemia). A disorderly or topographic distribution and reduction or disappearance of the cochlear succinic dehydrogenase and peroxidase reaction products were found in 37.8% of the rats fed on a basic iron-deficient diet for 14 to 100 days. The activity of cochlear sodium-potassium-dependent adenosine triphosphatase in iron-deficient rats was slightly increased, compared to that in normal controls. These results suggest that iron deficiency would produce significant abnormalities of succinic dehydrogenase and peroxidase activity, which in turn would disturb cell respiration and initiate peroxidative damage to the inner ear cells, result in sensorineural hearing loss, or provide a pathologic basis for cochlear deafness.

Anemia, Hypochromic↗
PubMed1987

Iron deficiency and hearing loss. Experimental study in growing rats.

Cochlear changes were studied in 141 growing rats raised on a basic iron-deficient diet for 7-100 days; 130 rats served as normal or chronic anemia controls. Electrophysiological findings showed that the incidence of an auditory threshold elevation of more than 15 dB was 31.85% in the iron-deficient rats, but it was unchanged in all the control animals. The main cochlear histopathological changes induced by iron deficiency were strial atrophy and reduction of spiral ganglion cells. It is concluded that the observed anomalies may be attributed solely to iron deficiency of the cochlear tissue.

Animals↗
PubMedDate not supplied

Pharmacokinetic profiles of ceftazidime in cochlear perilymph, cerebrospinal fluid and plasma: a high-performance liquid chromatographic study.

A pharmacokinetic profile of the antibiotic ceftazidime was established for perilymph, cerbrospinal fluid (CSF) and plasma in 12 guinea pigs using the technique of high-performance liquid chromatography. The mean peak levels of 13.35 mg/l in perilymph and 140.54 mg/l in plasma were reached within the first hour after a single intravenous dose of 100 mg/kg. The CSF mean peak level of 5.36 mg/l, however, was not attained until 3 h after injection. The half-life was about 4 h in perilymph, more than 6 h in CSF and less than 2 h in plasma. Six hours following administration, the perilymph drug concentration remained higher than the plasma level. The study indicates that ceftazidime has excellent penetration into perilymph. It is concluded that ceftazidime should be a very useful agent in the treatment of bacterial labyrinthitis caused by susceptible organisms.

Animals↗
PubMedDate not supplied

A scanning electron microscopic study of cochlear changes in iron-deficient rats.

The effects of iron deficiency on the cochlea were studied in growing rats fed with a basic iron-deficient diet for 80 days. The electrophysiological changes (auditory thresholds raised more than 15 dB) were observed in 47% of the cochleas of iron-deficient rats. When these organs of Corti were examined by scanning electron microscopy, abnormalities of outer or inner hair cells were found, as follows: (1) fusion and torsion of the stereocilia, (2) coalescence of adjacent stereocilia in the same row, (3) loss of sensory hair stiffness, and (4) loss of stereocilia. Within each lesion, the neighbouring supporting cells and their microvilli showed no damage. The findings indicate that cochlear impairment can be induced by iron deficiency. The peroxidative mechanisms responsible for the lesions of stereocilia in iron deficiency are discussed.

Anemia, Hypochromic↗