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Biomedical subjects

R F Clark

Publications and source records attributed to R F Clark.

At least 37 records · Page 2Linked to original sources
PubMed1999

Recurrent and persistent coagulopathy following pit viper envenomation.

BACKGROUND: Coagulation abnormalities following crotaline (pit viper) snakebite have traditionally been considered short-lived, but laboratory studies have rarely been reported beyond the first few days of treatment for envenomation. During the course of an antivenom clinical trial, we observed coagulation defects as late as 2 weeks following envenomation. OBJECTIVES: To document and characterize the recurrence or persistence of coagulopathy among patients envenomed by pit vipers and treated with a Fab antivenom. METHODS: Patients with moderate pit viper envenomation were enrolled in a multicenter, prospective clinical trial. A Fab-based antivenom preparation, antivenom polyvalent crotalid (ovine) Fab, was administered in all cases. Platelet count, fibrinogen level, presence of fibrin split products, prothrombin time, and partial thromboplastin time were determined before treatment and at standard intervals during the following 2 weeks. RESULTS: Of 38 patients completing the study, 20 (53%) had recurrent, persistent, or late coagulopathy 2 to 14 days after envenomation. Thrombocytopenia occurred in patients with prior thrombocytopenia; hypofibrinogenemia occurred only in those with prior hypofibrinogenemia or positive fibrin split products. No patient experienced significant spontaneous bleeding. One patient with coagulopathy developed minor bleeding following minor surgery 12 days after envenomation. CONCLUSIONS: Prolonged or recurrent coagulopathy may occur after envenomation by North American pit vipers. Patients treated with Fab-based antivenom may benefit from periodic rather than single-bolus dosing. Patients with coagulopathy should undergo close monitoring during the first 2 weeks after snakebite.

Adolescent↗
PubMed1999

Effect of magnesium hydroxide administration on iron absorption after a supratherapeutic dose of ferrous sulfate in human volunteers: a randomized controlled trial.

STUDY OBJECTIVE: Animal models have demonstrated that administration of magnesium hydroxide (MgOH) decreases serum iron levels after an iron overdose. We designed this study to determine the effect of MgOH administration on iron absorption and adverse effects after a supratherapeutic dose of ferrous sulfate in healthy male volunteers. METHODS: We conducted a prospective, unblinded, randomized trial involving 16 healthy, fasting men. All subjects ingested a 10-mg/kg dose of elemental iron in the form of ferrous sulfate. One-half hour after the iron dose, the 8 subjects in the experimental group were given 5 mg of MgOH for every 1 mg of ingested elemental iron. Serum iron levels were obtained at baseline and at each subsequent hour for 6 or 7 hours. Serum magnesium levels were obtained at baseline, after 3 hours, and after 6 hours. Side effects were recorded hourly. Serum iron levels between groups were compared by repeated-measures ANOVA and ANCOVA. The 95% confidence intervals (CIs) for the difference in serum iron levels between groups at each time point and for the difference in peak serum iron level between groups were calculated. RESULTS: Baseline mean serum iron levels did not differ between the 2 groups (P =.28). There were no statistical differences between groups (P =.20). Mean serum iron levels at each time point and peak serum iron levels did not differ significantly between groups. The mean peak serum iron level was 300.8 micrograms/dL in the control group and 272.5 micrograms/dL in the experimental group. CONCLUSION: Administration of MgOH does not affect iron absorption in humans after a supratherapeutic dose of iron when the ratio of MgOH to elemental iron is 5:1.

Adult↗
PubMed1999

Styrene-induced peripheral neuropathy.

CASE REPORT: Styrene is a colorless, oily liquid most commonly found in paints, plastics, and resins. Like many solvents, styrene can cause intoxication and central nervous system depression when inhaled in high concentrations for extended periods. Rarely, styrene has been implicated as a cause of peripheral neuropathy. We describe a case of a previously healthy 57-year-old man who developed signs and symptoms consistent with a peripheral neuropathy after applying a fiberglass resin to the inside of a septic tank over a 2-day period. Nerve conduction tests verified examination findings. Styrene exposure should be minimized through the use of respirators and protective clothing to prevent this type of toxicity.

Blood Pressure↗
PubMed1999

Comparison of the toxicities of two iron formulations in a swine model.

OBJECTIVE: To describe the histopathologic and pharmacokinetic differences of acute iron poisoning between chewable multivitamins with iron and solid iron tablets in a swine model. METHODS: This was a prospective, randomized, unblinded toxicity study of iron poisoning of two iron formulations in male Yorkshire pigs. Eight swine were randomized to receive 60 mg/kg of iron in either solid iron tablets or chewable multivitamins with iron. Serum iron, arterial blood gases, and episodes of vomiting were recorded over a ten-hour period. Routine histologic evaluations of the esophagus, stomach, small intestine, large intestine, and liver were performed immediately after the study period. Pharmacokinetic analyses of area under the concentration-time curve (AUC), time to peak concentration, and peak serum iron concentration were performed. RESULTS: There was no significant difference between the serum iron levels except at three and four hours. There was a significant higher AUC in the chewable group compared with the solid group. Pathologic evaluation identified severe esophageal inflammation and focal erosion in the solid iron tablet group in two of the four animals, compared with no focal erosions and minimal esophageal inflammation in the chewable group. No significant change was identified in the liver, small intestine, or large intestine in either group. CONCLUSIONS: These results demonstrate increased local gastrointestinal toxicity following a large ingestion of solid iron tablets in a swine model, compared with chewable multivitamins with iron. Higher serum iron levels were identified in the animals that received chewable multivitamins with iron.

Administration, Oral↗
PubMed1999

Ethanol analysis following consumption of "alcohol-free" beer.

Breath alcohol devices are routinely employed by emergency department personnel to reflect blood ethanol levels. No data have been published using these devices following the ingestion of "alcohol-free" beer that are required to contain < 0.5% alcohol. We performed a prospective, randomized, unblinded study on 8 healthy male volunteers that abstained from alcohol for 48 h and fasted for 10 h. Each subject ingested a 6-pack of alcohol-free beer over 1 h; breath alcohol determinations were made at 30, 60 and 120 min. Elevated breath alcohol levels were obtained at 30 and 60 min and decreased in all but 1 subject by 120 min. The elevated breath alcohol levels at 30 and 60 min may represent the previously reported "mouthwash" effect.

Adult↗
PubMed1999

The availability of activated charcoal and ipecac for home use.

Traditionally, ipecac has been used in the home; however, recently attention has focused on pre-hospital activated charcoal (AC) administration. In an effort to assess the availability of AC and ipecac, we conducted a telephone survey. One-hundred and 18 pharmacies were randomly selected from the 59 counties in California to assess availability of AC (liquid or powder) and/or ipecac. Ninety-four (80%) pharmacies participated. Seventy-nine of the pharmacies had ipecac compared to 8 which had AC. Three pharmacies had pre-mixed aqueous AC while 5 had AC in powder formulation. There was no difference between chains and community in AC or ipecac availability. The major limitations of effective GI decontamination are AC availability and rapidity in its administration. Our results identify a significant delay in the administration of AC if a parent was referred to a local pharmacy for home or pre-hospital decontamination. As more toxicologists and poison centers move towards pre-hospital and home AC much education of pharmacists as well as pediatricians and parents is required.

Charcoal↗
PubMed1999

A review of selected seafood poisonings.

Seafood poisoning has been recognized as a problem in both coastal and inland populations for millennia. Many types of sea creatures from shellfish to the largest fish have been implicated. Severe cases of many different types of seafood poisonings can result in fatalities. While the pathophysiology of the toxins is well known in some cases, others, like ciguatera, remain somewhat confusing. As a result, the treatment of these conditions remains controversial, although supportive care continues to be the mainstay of therapy. In this manuscript, we review the pathophysiology, clinical presentation, and treatment of some of the most common and toxic varieties of seafood poisoning resulting from toxins.

Animals↗
PubMed1999

Collecting information on disability in the 2000 Census: an example of interagency cooperation.

The United States Constitution requires that an enumeration (or census) of the population be conducted every 10 years to apportion seats in the House of Representatives. Census information is also used to allocate funds and to plan and manage programs. Census 2000 occurs on April 1, 2000, when one-sixth of all American households will be mailed the "long form," containing disability, demographic, economic, and housing questions. Although no short set of commonly accepted questions on disability existed, one was developed for Census 2000 by a collaborative, federal interagency work group on disability, convened by the Office of Management and Budget. The work group consisted of staff from the Social Security Administration (SSA), the Department of Health and Human Services, the U.S. Census Bureau, and other agencies. They reviewed questions initially proposed by the Census Bureau, developed an alternative proposal, tested both versions in the Census Bureau's cognitive questionnaire lab, and on the basis of testing, derived a consensus version for Census 2000. In many ways, the six questions now contained on Census 2000 are an improvement over previous efforts. Disability is ascertained for children as well as for adults, and information will be collected separately for several domains of disability (for example, sensory, mental, physical). The need for a brief set of disability measures goes beyond Census 2000. If such data were collected regularly on national surveys, critical policy and program concerns across agencies could be addressed because better information could be gathered on changes in disability prevalence and on the characteristics of persons with disabilities. Other similar efforts include the former Disability Evaluation Study, now known as the National Study of Health and Activity--a national sample survey on working-age disability to be conducted by SSA--and the President's Task Force on the Employment of Adults with Disabilities (Executive Order 13078).

Activities of Daily Living↗
PubMed1998

Resource-use analysis of a medical toxicology consultation service.

STUDY OBJECTIVE: To evaluate the impact of a medical toxicology consulting service (MTCS) on resource use and efficiency of care in patients hospitalized with a diagnosis of tricyclic antidepressant (TCA) poisoning. METHODS: We conducted a retrospective, case-controlled medical-records review at two urban tertiary care teaching hospitals. The study population comprised patients who presented to the emergency department with a diagnosis of TCA poisoning, in two phases. The first phase was longitudinal; we evaluated cases over 4 years before and after inception of an MTCS at one institution. In the second phase we compared consecutive cases of TCA poisoning treated at two urban teaching hospitals located within a mile of each other with similar patient populations, one with and one without MTCS backup. Inclusion criteria consisted of complete medical records, ingestion of first- and second-generation TCAs, and age greater than 16 years. Patients were excluded if history, physical examination, or laboratory analysis suggested that multiple substances had been ingested. Extensive demographic data were collected in each case. Clinical information obtained from each patient included admission vital signs, pupil size, QRS and corrected QT duration, and the presence of markers of severe TCA toxicity such as hypotension, seizures, pulmonary edema, respiratory insufficiency necessitating intubation, and the occurrence of antimuscarinic signs and symptoms. Information regarding treatment was also collected from each case, including laboratory tests, decontamination procedures, administration of sodium bicarbonate, and use of other medications and therapies. RESULTS: We identified a total of 88 patients in both phases of the study. Comparison groups were similar with respect to age, sex, presenting vital signs, presenting QRS and corrected QT duration, and incidence of recorded antimuscarinic signs, hypotension, seizures, and respiratory insufficiency requiring intubation. Total length of stay in a monitored hospital bed was also similar between groups. One fatality was recorded, but all other patients were discharged home or to a psychiatric facility. Patients seen by the MTCS consumed fewer health care resources in the form of less decontamination and fewer laboratory tests. CONCLUSION: The MTCS may provide a resource-efficient means of treating patients with TCA poisoning. A larger, multicenter study of a variety of poisoned patients should be undertaken to further investigate this issue.

Adolescent↗
PubMed1998

Clarithromycin induced digoxin toxicity.

A case of digoxin poisoning following the co-administration of digoxin and clarithromycin in a 28 year old male is described. Since the aetiology of chronic digoxin poisoning is often unclear, clinicians should be aware of the potential drug-drug interaction between digoxin and clarithromycin.

Adult↗
PubMed1998

An examination of serial urinalyses in patients with North American crotalid envenomation.

STUDY OBJECTIVE: To examine the incidence of abnormal urinalyses after rattlesnake envenomations and its association with bite severity and antivenom administration. METHODS: A retrospective review of data collected in a prospective manner for an experimental crotalid antivenom trial. Subjects were individuals with minimal to moderate North American crotalid envenomations. Incidence and characterization of abnormal urinalysis after crotalid envenomation is presented. Additionally, the relationship of abnormal urinalysis to bite severity is examined. A preliminary test of antivenom protein urinalysis interference was also conducted. RESULTS: Forty-three percent of the urinalyses reported prior to antivenom treatment had abnormalities. Thirty-three of 41 subjects (80%) had an abnormal urinalysis, defined as the presence of cells, blood, glucose, or protein, at some time during the 2-week period following envenomation. All but 3 of these subjects had urinalyses which returned to normal by 2 weeks postenvenomation. Fifteen of 22 subjects (68%) with minimal envenomations had an abnormal urinalysis at some time following envenomation, while 18 of 19 subjects (95%) with moderate envenomations had abnormal urinalyses (p < 0.05). In addition, high concentrations of antivenom added to urine were found to produce a positive urine dipstick test for protein. CONCLUSION: In our study of patients with minimal to moderate North American crotalid envenomations, there was a high incidence of abnormal urinalyses. The urine abnormalities tended to be more common with increased bite severity and more frequent during the first few hours following envenomation. Antivenom appearance in the urine could be responsible for some of our findings.

Adolescent↗
PubMed1998

Discovery of ascomycin analogs with potent topical but weak systemic activity for treatment of inflammatory skin diseases.

Drug therapy for the major inflammatory skin diseases, which include atopic dermatitis, psoriasis and allergic contact dermatitis, is often inadequate due to poor efficacy, toxicity, or both. Much research has focused on the macrolactam T cell inhibitors as a promising new class of agents for immunotherapy, and medicinal chemistry efforts to design novel ascomycin analogs have produced clinically promising agents. A synthetic program to modify the ascomycin nucleus to alter its physicochemical properties and promote systemic clearance is described. A biologic screening strategy to identify analogs with reduced systemic activity and rapid pharmacokinetic elimination led to identification of the clinical candidate, ABT-281. A swine contact hypersensitivity model was used as a stringent indicator of skin penetration as human doses of topical corticosteroids produced inhibition only in the 50% range and ED50 values were 100-fold less potent than in rat. Also, cyclosporine was confirmed to be topically inactive in swine, as seen in human. ABT-281 had topical potency equal to tacrolimus (FK506) despite a severalfold lower potency for inhibiting swine T cells in vitro, consistent with superior skin penetration. ABT-281 was found to have a shorter duration of action after i.v. dosing in monkeys using an ex vivo whole blood IL-2 production assay. Systemic potency was reduced by 30-fold or more in rat popliteal lymph node hyperplasia and contact hypersensitivity assays. Following i.v. or i.p. administration in the swine contact hypersensitivity model, ABT-281 was 19- and 61-fold less potent, respectively, than FK506. Pharmacokinetic studies showed that ABT-281 had a shorter half life and higher rate of clearance than FK506 in all three species. The potent topical activity and reduced systemic exposure of ABT-281 may thus provide both efficacy and a greater margin of safety for topical therapy of skin diseases.

Administration, Topical↗
PubMed1997

Clarithromycin-induced ventricular tachycardia.

Clarithromycin is a relatively new macrolide antibiotic that offers twice-daily dosing. It differs from erythromycin only in the methylation of the hydroxyl group at position 6. Although the side-effect profile of erythromycin is established, including gastroenteritis and interactions with other drugs subject to hepatic mixed-function oxidase metabolism, experience with the newer macrolides is still being recorded. Cardiotoxicity has been demonstrated after both intravenous and oral administration of erythromycin but has never been reported with the newer macrolides. We report a case of ventricular dysrhythmias that occurred after six therapeutic doses of clarithromycin. The dysrhythmias resolved after discontinuation of the drug.

Adult↗