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Biomedical subjects

J M Christensen

Publications and source records attributed to J M Christensen.

At least 91 records · Page 5Linked to original sources
PubMed1985

Effects of oral cimetidine on plasma concentrations of phenylbutazone in horses.

Phenylbutazone was administered to six Thoroughbred horses in a cross-over study in which the horses received cimetidine pretreatment or no cimetidine pretreatment. Blood samples were collected at various times for 48 h after phenylbutazone administration and the plasma was analysed for phenylbutazone. Cimetidine pretreatment elevated phenylbutazone plasma concentrations during the first 8 h after phenylbutazone administration. The absorption rate, maximum phenylbutazone plasma concentrations and AUC were significantly greater with cimetidine pretreatment. The half-life of phenylbutazone did not change with cimetidine pretreatment; however, lower plasma concentrations of the metabolite gamma-hydroxyphenylbutazone were observed with cimetidine pretreatments. Plasma concentrations of the metabolite oxyphenbutazone were unchanged with cimetidine pretreatment compared to control values. Twenty-four-hour plasma concentrations of phenylbutazone were not different from control values with cimetidine pretreatment. This study suggests that concurrent treatment with cimetidine and phenylbutazone 24 h before race time does not result in elevations of plasma phenylbutazone concentrations above control values.

Administration, Oral↗
PubMed1985

Norethindrone disposition following x-ionizing radiation in rats.

The pharmacokinetics of norethindrone were investigated in rats exposed to ionizing x-irradiation. Norethindrone was administered by IV bolus injection immediately after, 3 days or 7 days after exposure to 100 rads, 300 rads, 600 rads, and sham x-irradiation. No observable change in norethindrone pharmacokinetics was observed in rats immediately after exposure to all dose levels of x-rays. At three days post irradiation there was an increase in volume of distribution (Vdarea) from 5.55 +/- 0.93 l/kg for sham irradiated to 11.28 +/- 0.74 l/kg for 600 rad rats. Half-life increased after exposure to x-rays from 45.2 +/- 4.5 minutes for sham irradiated to 85.5 +/- 12.1 minutes for 600 rads dose. The Mean Residence Time (MRT) increased from 56.7 +/- 5.6 minutes to 96.4 +/- 13.6 minutes after exposure to 600 rads. This same trend was present 7 days post irradiation but was not nearly as pronounced. No significant differences were observed in total body clearance in irradiated versus sham irradiated animals. As norethindrone is excreted as metabolites via hepatic biotransformation, these findings imply that this process is not affected by irradiation for drugs with high hepatic extraction ratios. Increased distribution of norethindrone to peripheral tissues results in a longer MRT for irradiated animals which could result from radiation induced increase in membrane permeability.

Animals↗
PubMed1985

Stability of an analgesic-sedative combination in glass and plastic single-dose syringes.

The stability of a combination of chlorpromazine hydrochloride (6.25 mg/mL), hydroxyzine hydrochloride (12.5 mg/mL), and meperidine hydrochloride (25 mg/mL) in glass and plastic syringes was studied. Syringes (glass 1.5 mL, plastic 3.0 mL) containing the combination drug solution were stored at 4, 25, and 44 degrees C. At 0,7,30,60,90,180, and 366 days after preparation, samples were visually inspected and tested for pH. Drug concentrations were determined by gas chromatography. No significant changes in drug concentration were apparent in any of the samples stored at 4 degrees C or 25 degrees C. Samples in both glass and plastic syringes stored at 44 degrees C turned yellow by day 30 and continued to darken throughout the study period. At the concentrations tested, chlorpromazine hydrochloride, hydroxyzine hydrochloride, and meperidine hydrochloride combined in glass or plastic syringes are stable for 366 days when stored at 4 degrees C and 25 degrees C. Degradation occurs at higher temperatures.

Chlorpromazine↗
PubMed1985

Ethyl lactate-ethanol-water cosolvent for intravenous theophylline.

Theophylline was dissolved in an ethyl lactate-ethanol-water cosolvent system and administered intravenously to rabbits. There were no observed differences in theophylline pharmacokinetics in rabbits administered in the cosolvent system when compared to theophylline administered as Aminophylline Injection USP, with the half-life being 4.5 hours and 4.3 hours respectively. Theophylline dissolved in the cosolvent system caused less erythrocyte hemolysis when exposed to blood in vitro than Aminophylline Injection USP. There were no observed toxicities in any rabbits during intravenous administration of theophylline dissolved in the cosolvent system or for Aminophylline Injection USP.

Animals↗
PubMed1984

Effects of divalent amino acids on iron absorption.

Solutions of each of 10 amino acids or ascorbic acid were mixed with iron and orally administered to rats. Iron was absorbed to a statistically significantly greater extent (p less than 0.05) when mixed with asparagine, glycine, serine, or ascorbic acid as compared with a control solution of iron. The largest effects were for asparagine and glycine, which also increased iron absorption to a significantly greater extent (p less than 0.001) than did serine or ascorbic acid. No statistically significant increase in iron absorption occurred when any of the other amino acids was mixed with iron. The extent of iron absorption from each test solution, as measured by area under the concentration of iron-59 in the blood-time curve (r2 = 0.0002), and the initial rate of iron absorption for each test solution (r2 = 0.01) showed no correlation with the stability constant of the amino acid-iron complex.

Amino Acids↗
PubMed1984

Neutron activation of iron tablets to evaluate the effects of glycine on iron absorption.

Neutron bombardment (neutron flux, 3 X 10(12) neutrons/cm2/s) of prepared iron tablets containing glycine-iron or iron alone was performed to prepare radioactive tablets to assess the effects of glycine on iron absorption from tableted formulations. No interfering isotopes of sufficient quantity were generated during neutron activation of the iron tablets. Cobalt-60 was the major trace mineral detected and accounted for only 1.3% of the total activity. There may have been trace amounts of zinc-65 or chromium-51 present, but they were not detectable above background radioactivity in the final tablet produced. Iron-59 represented greater than 98% of the radioactivity present in the tablets used in the study. Glycine-containing iron tablets produced dramatically higher amounts of iron in blood and tissues of rabbits (p less than 0.05) than did the same tablet formulations without glycine. The area under the iron blood concentration-time curve over 4 h increased by 67% with glycine added to the formulation over control iron tablets. Iron concentrations in tissues 4 h after iron administration was in the order of blood greater than liver greater than heart greater than kidney greater than muscle.

Animals↗
PubMed1984

The prehospital use of external counterpressure: does MAST make a difference?

Military anti-shock trousers (MAST) have achieved widespread civilian usage because of reported effectiveness in treating hypovolemic shock. The literature, however, consists of either case reports or series in which no controls were evaluated. No published reports exist which compare similar groups of patients treated with and without MAST in the pre-hospital setting. We reviewed the paramedic and emergency department records of 226 patients sustaining moderate to severe trauma who were transported to San Francisco General Hospital by paramedics over a 15 month period. MAST usage during this period was approximately random as a result of logistical and training constraints. For analysis, patients were divided into two groups: those in whom MAST was applied and inflated during transport and those in whom it was not used. Paramedic interventions other than MAST were similar in both groups. Trauma Scores (TS), and blood pressure index (greater than 90 = 4, 70-89 = 3, 50-69 = 2, 0-49 = 1, no pulse = 0), were calculated for initial field observations and initial emergency room evaluation after hospital arrival. Patients with isolated head injury were excluded. The average change in TS and BP index (E.R.--field value) was calculated for MAST and non-MAST groups of patients. Mortality and total field times were also evaluated. Average TS and BP index increased slightly in both groups. Use of MAST produced no significant improvement in trauma score, BP index, or mortality over non-MAST patients. There was no demonstrable field benefit of MAST in fully arrested patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1984

Influence of cimetidine on the disposition of ibuprofen in the rat.

Ibuprofen is a non-steroidal anti-inflammatory agent which is extensively metabolized in both man and the rat. Cimetidine is a well known H2 antagonist which is known to inhibit microsomal enzyme drug metabolism. The influence of cimetidine on the disposition of ibuprofen was studied in Sprague-Dawley rats. Pretreatment with cimetidine was found to increase both the rate and extent of absorption of ibuprofen. Cimetidine treatment also inhibited acidification of gastric fluid. Pretreatment with SKF525A increased ibuprofen half-life but not absorption. Additional studies are necessary to determine the effect of cimetidine on the half-life and absorption of ibuprofen in man.

Animals↗
PubMed1983

In vivo release of norethindrone coupled to a biodegradable poly(alpha-amino acid) drug delivery system.

The in vivo release of norethindrone from a biodegradable steroid-polymer conjugate was studied in rats. The drug-polymer conjugate, consisting of [3H]norethindrone coupled via a 17-carbonate bond to poly-N5-(3-hydroxypropyl)-L-glutamine was administered to female rats by subcutaneous injection. The in vivo release of steroid, determined by measuring the daily radioactivity output in urine and feces, was fairly constant though it showed a gradual decrease during the 9-month study period. The data indicate that this biodegradable norethindrone-polymer conjugate is a potential candidate for the controlled delivery of norethindrone to effect long-term contraception.

Animals↗
PubMed1983

Evaluation of the effects of palatal augmentation on partial glossectomy speech.

Patients who have had surgical removal of part of the tongue are left with varying degrees of speech deficiencies. Augmentation of the palate has been suggested as a means of compensation for this deficiency. This pilot study suggests a technique for evaluating prosthodontic efforts to improve speech for partial glossectomy patients. Although firm conclusions cannot be based on the observations of one patient, it appears that both the shape of the palatal surface and the contour of the cavity size anterior to the tongue are important factors to be considered in prosthodontic efforts to optimize fricative sound production for partial glossectomy patients. Further studies with patients who have a wider variety of tongue resections are indicated. The technique described is an effective one for further studies.

Evaluation Studies as Topic↗
PubMed1983

Effect of inhalation injury on lung water accumulation.

Fourteen thermally injured patients with severe inhalation injury were sequentially studied with the thermal-green dye double indicator dilution technique of extravascular lung water (EVLW) measurement. Eight females and six males (average age, 49 years, and average thermal burn, 37% body surface) were studied for 2-31 days postinjury. All were burned in a closed space, had facial burns, soot in their sputum, and a mean carboxyhemoglobin level of 30%. Nine patients died, six of sepsis, one each of acute renal failure, hepatorenal syndrome, and anoxic brain damage. Mean EVLW on admission was 7.0 +/- 2.9 ml/kg and remained normal in the five survivors and in the patients dying of acute renal failure and anoxic brain damage. Six patients had increases in EVLW, caused by altered pulmonary capillary permeability in five and by elevation of hydrostatic pressures in one patient (hepatorenal death). Of the five patients with permeability edema, one appeared to result from a direct early effect of inhalation injury resulting in an EVLW of 13.3 ml/kg on admission. The other four patients had EVLW increases after the onset of sepsis, resulting in a mean EVLW of 23.2 +/0- 7.2 ml/kg at death (p less than 0.01). Seventy-one per cent of all patients developed pneumonia, which appears to have caused an EVLW increase in one patient; the other EVLW increases were caused by systemic sepsis. In our present study of 14 patients with definite severe inhalation injury only one had an early increase in EVLW directly related to the inhalation injury, an early effect on capillary permeability presumably caused by direct chemical toxicity of inhaled gases. The remaining four cases of permeability edema occurred 4-24 days postinjury and resulted from burn wound or pulmonary sepsis. We thus conclude that increases in EVLW after thermal and inhalational injury are primarily caused by systemic or pulmonary sepsis, and have a delayed onset. Early increases in EVLW may be a result of the chemical toxicity of inhaled gases but are very uncommon, moderate in degree, and are seen only with the severest cases of inhalation injury.

Adult↗
PubMed1983

Pulmonary extravascular fluid accumulation following intracranial injury.

Previous investigations have reported an 11 to 71% incidence of pulmonary edema following CNS injury, based on post-mortem examinations. No premortem assessment to date has been made of the frequency and severity of in vivo pulmonary fluid accumulation following acute head injury. The thermal green dye technique was used to objectively determine extravascular lung water (EVLW) in 18 comatose patients with severe acute intracranial injuries resulting from trauma or spontaneous subarachnoid hemorrhage. Patients with aspiration, lung contusion, or pneumonia were excluded from the study. Control values for EVLW were obtained on admission from a group of 13 traumatized patients without head injury or evidence of pulmonary disease or injury. Intracranial injury patients who had EVLW values greater than two standard deviations above the control group mean were considered to have pulmonary edema. The incidence of pulmonary edema in this series was 50% (9/18). Extravascular lung water was determined post mortem in five patients using the gravimetric method of Pearce. The results suggest that pulmonary edema is a distinct clinical event occurring frequently after acute intracranial injury. Edema appears to be mediated by increased pulmonary microvascular permeability, and is not primarily dependent on postinjury changes in intracranial pressure or pulmonary vascular pressures.

Blood Pressure↗
PubMed1983

Progabide: a controlled trial in partial epilepsy.

Progabide (SL 76002) was studied in a randomized double-blind crossover trial using 20 outpatients suffering from partial complex seizures. Progabide was added to the concomitant antiepileptic treatment in a fixed dosage schedule. The design included an open therapy control unit. No significant difference was established between the number of partial seizures during treatment with progabide and placebo. A trend was observed for lower seizure frequency of secondary generalized seizures during treatment with progabide. Only mild and transient side effects were observed. There was no difference between the side effects of progabide and placebo.

Anticonvulsants↗