(1/216) Dental anesthetic management of a patient with ventricular arrhythmias.
During routine deep sedation for endodontic therapy, a dentist-anesthesiologist observed premature ventricular contractions (PVCs) on a 62-yr-old woman's electrocardiogram (EKG) tracing. The dentist was able to complete the root canal procedure under intravenous (i.v.) sedation without any problems. The dentist-anesthesiologist referred the patient for medical evaluation. She was found to be free from ischemic cardiac disease with normal ventricular function. The patient was cleared to continue her dental treatment with deep sedation. She subsequently continued to undergo dental treatment with deep intravenous sedation without incident, although her EKG exhibited frequent PVCs, up to 20 per minute, including couplets and episodes of trigeminy. This article will review indications for medical intervention, antiarrhythmic medications, and anesthetic interventions for perioperative PVCs. (+info)
(2/216) Transport characteristics of diphenhydramine in human intestinal epithelial Caco-2 cells: contribution of pH-dependent transport system.
Transport characteristics of diphenhydramine, an antihistamine, were studied in cultured human intestinal Caco-2 cell monolayers to elucidate the mechanisms of its intestinal absorption. Diphenhydramine accumulation in the monolayers increased rapidly and was influenced by extracellular pH (pH 7.4 > 6.5 > 5.5). Diphenhydramine uptake was temperature dependent, saturable, and not potential sensitive. Kinetic analysis revealed that the apparent Km values were constant (0.8-1.0 mM) in all pH conditions tested, whereas Vmax values decreased at the lower pH. The initial uptake of diphenhydramine was competitively inhibited by another antihistamine, chlorpheniramine, with a Ki value of 1.3 mM. On the other hand, cimetidine and tetraethylammonium, typical substrates for the renal organic cation transport system, had no effect. Moreover, biological amines and neurotransmitters, such as histamine, dopamine, serotonin, and choline, also had no effect on the diphenhydramine accumulation. Finally, diphenhydramine uptake was stimulated by preloading monolayers with chlorpheniramine (trans-stimulation effect). These findings indicate that diphenhydramine transport in Caco-2 cells is mediated by a specific transport system. This pH-dependent transport system may contribute to the intestinal absorption of diphenhydramine. (+info)
(3/216) Safety and efficacy of a continuous infusion, patient controlled anti-emetic pump to facilitate outpatient administration of high-dose chemotherapy.
We evaluated the combination of diphenhydramine, lorazepam, and dexamethasone delivered as a continuous i.v. infusion via an ambulatory infusion pump with patient-activated intermittent dosing (BAD pump) for prevention of acute and delayed nausea/vomiting in patients receiving high-dose chemotherapy (HDC) for peripheral blood progenitor cell (PBPC) mobilization (MOB) or prior to autologous PBPC rescue. The BAD pump was titrated to patient response and tolerance, and continued until the patient could tolerate oral anti-emetics. Forty-four patients utilized the BAD pump during 66 chemotherapy courses, 34 (52%) for MOB and 32 (48%) for HDC with autologous PBPC rescue. The median number of days on the BAD pump during MOB and HDC was 3 (1-6) and 9 (2-19) days, respectively. Complete overall or complete emesis control occurred on 94% of MOB and 89% of HDC treatment days during chemotherapy administration and 72% and 43%, respectively, following chemotherapy administration. Eighty-three percent of MOB and 55% of HDC treatment days were associated with no nausea. While on the BAD pump, no patient experienced severe toxicity or required hospitalization for management of nausea/vomiting. The BAD pump was safe and effective in minimizing nausea and vomiting associated with HDC, and thus, eliminated the need for hospitalization for management of chemotherapy-induced nausea and vomiting. (+info)
(4/216) Examination of low-incidence brain tumor responses in F344 rats following chemical exposures in National Toxicology Program carcinogenicity studies.
Neoplasms in the brain are uncommon in control Fischer 344 (F344) rats; they occur at a rate of less than 1% in 2-yr toxicity/carcinogenicity studies. Furthermore, only 10 of nearly 500 studies conducted by the National Toxicology Program (NTP) showed any evidence of chemically related neoplastic effects in the brain. Generally, the brain tumor responses were considered equivocal, because the characteristics of potential neurocarcinogenic agents (such as statistically significant increased incidences, decreased latency and/or survival, and demonstration of dose-response relationships) were not observed. A thorough examination, including comparisons with a well-established historical database, is often critical in evaluating rare brain tumors. Chemicals that gave equivocal evidence of brain tumor responses were generally associated with carcinogenicity at other sites, and many chemicals were mutagenic when incubated with metabolic activating enzymes. Other factors that were supportive of the theory that marginal increases in brain tumor incidence were related to chemical exposure were that (a) some of the tumors were malignant, (b) no brain neoplasms were observed in concurrent controls from some studies, and/or (c) brain tumors were also seen following exposure to structurally related chemicals. In 2-yr studies in F344 rats (studies conducted by the NTP), equivocal evidence of carcinogenicity was observed for the following 9 chemicals: isoprene, bromoethane, chloroethane, 3,3'-dimethylbenzidine dihydrochloride, 3,3'-dimethoxybenzidine dihydrochloride, furosemide, C.I. direct blue 15, diphenhydramine hydrochloride, and 1-H-benzotriazole. Glycidol was the only chemical evaluated by the NTP with which there was clear evidence of brain tumor induction in F344 rats. Clarification of the potential neurocarcinogenic risks of chemicals that produce equivocal evidence of a brain tumor response in conventional 2-yr rodent studies may be aided by the use of transgenic mouse models that exhibit genetic alterations that reflect those present in human brain tumors as well as by the use of in utero exposures. (+info)
(5/216) Inhibition of Na(+) current by diphenhydramine and other diphenyl compounds: molecular determinants of selective binding to the inactivated channels.
Diphenhydramine is an H1 histamine receptor antagonist, yet it also has a clinically useful local anesthetic effect. We found that diphenhydramine inhibits the neuronal Na(+) current, and the inhibition is stronger with more positive holding potentials. The dissociation constant between diphenhydramine and the inactivated Na(+) channel is approximately 10 microM, whereas the dissociation constant between diphenhydramine and the resting channel is more than 300 microM. The local anesthetic effect of diphenhydramine thus is ascribable to inhibition of Na(+) current by selective binding of the drug to the inactivated channels. Most interestingly, many other compounds, such as the anti-inflammatory drug diclofenac, the anticonvulsant drug phenytoin, the antidepressant drug imipramine, and the anticholinergic drug benztropine, have similar effects on neuronal Na(+) current. There is no apparent common motif in the chemical structure of these compounds, except that they all contain two phenyl groups. Molecular modeling further shows that the two benzene rings in all these drugs have very similar spatial orientations (stem bond angle, approximately 110 degrees; center-center distance, approximately 5 A). In contrast, the two phenyl groups in phenylbutazone, a drug that has only a slight effect on Na(+) current, are oriented in quite a different way. These findings strongly suggest that the two phenyl groups are the key ligands interacting with the channel. Because the binding counterpart of a benzene ring usually is also a benzene ring, some aromatic side chain groups of the Na(+) channel presumably are realigned during the gating process to make the very different affinity to the aforementioned drugs between the inactivated and the resting channels. (+info)
(6/216) Paclitaxel-associated hypersensitivity reactions: experience of the gynecologic oncology program of the Cleveland Clinic Cancer Center.
PURPOSE: : This study expands the existing limited data as to whether patients developing clinically significant paclitaxel-induced hypersensitivity reactions can continue to be treated with this important antineoplastic agent and how such retreatment might be undertaken. PATIENTS AND METHODS: More than 450 patients received paclitaxel, either as a single agent or in a combination regimen, for a female pelvic malignancy in the Gynecologic Oncology Program of the Cleveland Clinic Cancer Center from January 1995 through December 1998. RESULTS: Of the more than 450 patients, 44 (approximately 9%) developed at least one episode of a clinically relevant hypersensitivity reaction to the cytotoxic drug. All 43 individuals (plus an additional four patients referred to our center after having previously experienced a severe paclitaxel-associated hypersensitivity reaction at another institution) who were retreated with paclitaxel were ultimately able to receive the agent. Five patients required treatment with a standardized desensitization regimen, developed by our group, to successfully receive paclitaxel. DISCUSSION: On the basis of this large single-institution study of paclitaxel-associated hypersensitivity reactions, we conclude that with appropriate precautions essentially all individuals experiencing these reactions can be safely treated with this agent. (+info)
(7/216) Concentration-effect relationship of intravenous lidocaine on the allodynia of complex regional pain syndrome types I and II.
BACKGROUND: Several lines of evidence suggest that neuropathic pain (including Complex Regional Pain Syndrome [CRPS] I and CRPS II) is mediated in part by an increase in the density of voltage-sensitive sodium channels in injured axons and the dorsal root ganglion of injured axons. This study sought to characterize the effects of intravenous lidocaine (a sodium channel blocker) on acute sensory thresholds within the painful area and the size of the painful area in patients suffering from CRPS I and II. METHODS: This study used a randomized, double-blind, placebo-controlled design in 16 subjects suffering from CRPS I and II with a prominent allodynia. Each subject received an intravenous infusion of lidocaine and diphenhydramine separated by 1 week. A computer-controlled infusion pump targeted stair-step increases in plasma levels of lidocaine of 1, 2, and 3 microg/ml. At baseline and at each plasma level, spontaneous and evoked pain scores and neurosensory testing within the painful area were measured. The neurosensory testing consisted of thermal thresholds, tactile thresholds and the area of allodynia to punctate, and stroking and thermal stimuli. RESULTS: Intravenous lidocaine and diphenhydramine had no significant effect on the cool, warm, or cold pain thresholds. However, lidocaine caused a significant elevation of the hot pain thresholds in the painful area. Intravenous lidocaine caused a significantly decreased response to stroking and cool stimuli in the allodynic area. There was also a significant decrease in pain scores to cool stimuli at all plasma levels and the spontaneous pain at the highest plasma level. CONCLUSIONS: This study demonstrates that intravenous lidocaine affects pain in response to cool stimuli more than mechanical pain in subjects with neuropathic pain. There is a lesser effect on spontaneous pain and pain induced by stroking stimuli and no effect on the pain induced by punctate stimuli. (+info)
(8/216) Diphenhydramine disposition in the sheep maternal-placental-fetal unit: gestational age, plasma drug protein binding, and umbilical blood flow effects on clearance.
The objective of this study was to examine the interrelationships between maternal and fetal plasma drug protein binding, umbilical blood flow (Q(um)), gestational age (GA), and maternal-fetal diphenhydramine (DPHM) clearances in chronically instrumented pregnant sheep. Maternal and fetal DPHM placental (CL(mf) and CL(fm), respectively) and nonplacental (CL(mo) and CL(fo), respectively) clearances and steady-state plasma protein binding were determined in 18 pregnant sheep at 124 to 140 days' gestation (term, approximately 145 days). The data demonstrated a highly significant fall of approximately 66% in CL(fm) and a decreasing trend in CL(fo) ( approximately 47%) over the GA range studied. However, no such relationships existed between GA and CL(mf) or CL(mo). Concomitant with this was a decrease in fetal DPHM plasma unbound fraction with GA, with no such change being evident in the mother. Both CL(mo) and CL(fo) were related to the respective DPHM plasma unbound fraction. A strong relationship also existed between fetal plasma unbound fraction and CL(fm). Thus, the decrease in fetal unbound fraction of DPHM during gestation could contribute to the fall in CL(fm), and possibly CL(fo). However, over the GA range studied, fetal DPHM free fraction decreased by approximately 47%, whereas CL(fm) fell by approximately 66%. Because fetal unbound fraction and CL(fm) are linearly related, the GA-associated fall in unbound fraction appears to be insufficient to account for the entire decline in CL(fm). In separate studies in pregnant sheep, we observed a approximately 40% fall in weight-normalized Q(um) between 125 and 137 days' gestation. Because CL(fm) for DPHM is similar to that of flow-limited compounds (e.g., ethanol, antipyrine), this decrease in Q(um) may also contribute to the GA-related fall in CL(fm). (+info)