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Biomedical subjects

G J Grant

Publications and source records attributed to G J Grant.

At least 19 recordsLinked to original sources
PubMed2003

Analgesic duration and kinetics of liposomal bupivacaine after subcutaneous injection in mice.

1. The objective of the present study was to assess the time-course profile of analgesia and bupivacaine concentrations at the site of injection after subcutaneous administration of a single dose of standard bupivacaine or a novel controlled-release liposomal bupivacaine formulation. 2. Groups of mice were injected subcutaneously with 0.2 mL of 0.5% standard bupivacaine or 0.5, 1 or 2% liposomal bupivacaine. 3. A prolonged duration of analgesia occurred in mice receiving liposomal bupivacaine. In the liposomal groups, the bupivacaine remained at the injection site for more than 96 h, compared with approximately 8 h in groups injected with standard bupivacaine. 4. These results confirm that the prolonged analgesia observed after injection of the liposomal formulation is associated with sustained higher levels of bupivacaine at the site of injection.

Analgesia↗
PubMed2002

Intrathecal administration of liposomal neostigmine prolongs analgesia in mice.

BACKGROUND: There is substantial evidence that cholinomimetic drugs increase pain threshold. However, the profound side effects of these agents have limited their clinical use either as analgesics or as analgesic adjuncts. A delivery system that would assure a slow and sustained drug release may be of value in ameliorating the problem of untoward effects. METHODS: The acetylcholinesterase inhibitor neostigmine was encapsulated into multilamellar lipid vesicles composed of phosphocholine and cholesterol. Three doses of plain or liposomal neostigmine were administered by the intrathecal route to mice (n=8-10/group), and analgesic duration was quantified by tail flick test. The doses were chosen based on preliminary experiments, which showed the maximum tolerated intrathecal doses of plain and liposomal neostigmine formulation were 0.625 microg and 80 microg, respectively. Two other doses for each formulation were then derived by 1:1 serial dilutions. Results were compared using survival analysis. RESULTS: The median antinociceptive duration for plain neostigmine was 0.33, 0.99 and 1.0 h for the 0.115, 0.312 and 0.625 microg doses, respectively. For the liposomal formulation, the median antinociceptive duration was 1.0, 1.5 and 6.0 h for the 20, 40 and 80 microg doses, respectively. CONCLUSIONS: Liposomal neostigmine provides prolonged spinal antinociception, and permits the safe administration of a relatively large dose, because drug is gradually released from the liposomal depot. This technology holds promise for the development of a clinically useful neostigmine formulation to provide spinal analgesia.

Analgesia, Epidural↗
PubMed2001

Quantifiable dose-dependent withdrawal after morphine discontinuation in a rat model.

We evaluated the intensity of the withdrawal symptoms after the discontinuation of the morphine infusion in rats. Opiate addiction was induced by progressively increasing intraperitoneal morphine infusion rates. The control group (Group 1) received normal saline. The initial morphine rates were 1, 4, and 16 mg kg(-1) h for Groups 2, 3, and 4, respectively. Infusion rates were gradually increased by a factor of 1.4, 2, 2.8, and 4 on the second, third, fourth, and fifth days, respectively. The last rate was used for 48 h and then infusions were disconnected. Weight reduction, food consumption, and water intake were used for evaluation of withdrawal. All morphine groups showed a significant reduction of body weight during the 4 postdiscontinuation days and a decline in food and water intake on the first postdiscontinuation day. All changes were dependent on the morphine infusion concentration. No changes were observed in the control group. We suggest that the rat model used in this study may be utilized for quantification of spontaneous withdrawal.

Animals↗
PubMed2001

DRV liposomal bupivacaine: preparation, characterization, and in vivo evaluation in mice.

PURPOSE: To evaluate the dehydration-rehydration technique to prepare a formulation of liposomal bupivacaine, and to assess its analgesic efficacy. METHODS: Bupivacaine hydrochloride (BUP) was encapsulated into dehydration-rehydration vesicles (DRV) of varying phospholipid (PL) compositions. Two bilayer-forming phospholipids were used, the "fluid" dimyristoyl-phosphatidylcholine and the "solid" distearoyl-phosphatidylcholine (DSPC), with 20 or 40 mol% cholesterol, in the presence of bupivacaine at a 1.28 or 0.64 BUP/PL mole ratio. After rehydration, drug/lipid ratios were determined. The formulation with the highest drug/lipid ratio (DSPC/cholesterol in an 8:2 mole ratio prepared in the presence of bupivacaine in a 1.28 BUP/PL mole ratio) was adjusted to a final bupivacaine concentration of 3.5% or 0.5%. The duration of skin analgesia after subcutaneous injection in mice produced by these formulations was compared with the conventional administration of a plain 0.5% solution of BUP. In addition, the concentration of residual bupivacaine at the injection site was followed for 96 h. RESULTS: The relatively low organic solvent/aqueous phase and membrane/aqueous phase partition coefficients, together with liposomal trapped volume and BUP/PL mole ratio, indicated that most of the drug was encapsulated in the intraliposome aqueous phase of the DRV. The DSPC/cholesterol 8:2 mole ratio had the best drug encapsulation (BUP/PL = 0.36). Compared to plain BUP, these BUP-DRV produced significant prolongation of analgesia, which is explained by longer residence time of the drug at the site of injection. CONCLUSIONS: Bupivacaine-DRV may have a role in achieving safe, effective, and prolonged analgesia in humans.

Anesthetics, Local↗
PubMed2001

Perineural antinociceptive effect of opioids in a rat model.

BACKGROUND: The research on conductive analgesia induced by perineural opioids generated a large body of conflicting data. In this study we reassessed the antinociceptive response to perineural administration of morphine, fentanyl or meperidine in a rat model. METHODS: Analgesia was assessed using the hind paw withdrawal latency (HPWL) response to radiant heat. The opioid dose producing 20% of maximal possible effect (20%MPE) for systemic analgesia was calculated for each drug. Then sciatic blockade was performed with the dose corresponding to 20%MPE. The injected hind paw was used to measure direct perineural effect and the contralateral hind paw was used as an indicator of systemic effect. RESULTS: The response latency produced by morphine or fentanyl was not significantly different for ipsilateral (perineural effect) or contralateral (systemic effect) paw (27+/-11 vs. 28+/-16 and 3l+/-16 vs. 23+/-16 s, respectively). However, the meperidine group showed significantly higher %MPE for the ipsilateral paw (79+/-32 s) than for the contralateral paw (27+/-22 s). CONCLUSIONS: The results indicate that perineural fentanyl or morphine do not produce analgesia. Perineural block produced by meperidine was attributed to local anesthetic-like effect, rather than to drug interaction with opioid receptor.

Analgesia↗
PubMed1997

Effect of intrathecally administered local anesthetics on protein phosphorylation in the spinal cord.

To elucidate the biochemical mechanisms of spinal anesthesia, we studied the effects of procaine and tetracaine on protein phosphorylation in the mouse spinal cord. Mice were injected intrathecally with either procaine, tetracaine (67 mM/approximately 2%, 10 microL, N = 5/drug), or saline (N = 4/group). Five minutes after injection, animals were killed with a guillotine, and the spinal cord was removed. The caudal 3-cm cord segment was homogenized and centrifuged, and an aliquot of the supernatant was used for phosphorylation assays. Calcium-dependent phosphorylation was initiated by incubating the samples in buffer containing [gamma-32P]ATP at 37 degrees for 30 min. The proteins were electrophoresed using slab gel and two-dimensional electrophoresis, and phosphorylated proteins were visualized by autoradiography. The data demonstrated that spinal anesthesia changes the phosphorylation state of five endogenous substrate proteins with apparent molecular masses of 130 (protein-a), 105 (protein-b), 55 (protein-c), 47 (protein-d), and 33 (protein-e) kDa. In two-dimensional electrophoresis, protein-a resolved into two proteins (a1 and a2). Analysis of variance of the densitometric data suggested a significant effect for the treatment (F(2,16) 735, P < 0.00005). Post hoc comparisons with the saline-treated controls, using the Newman-Keuls test, indicated that local anesthetics significantly affected phosphoproteins (P < 0.05) except for protein-al in the tetracaine-treated group. Further characterization of these phosphoproteins should aid in determining their role in the signal transduction cascade affected by spinal anesthesia.

Anesthetics, Local↗
PubMed1997

Sufentanil transfer in the human placenta during in vitro perfusion.

PURPOSE: Sufentanil, a lipophilic opioid, is used to provide analgesia for labour and Caesarean section, but may cause neonatal depression. Factors affecting placental transfer of sufentanil were investigated using human placentas. STUDY DESIGN: Transfer and uptake of sufentanil by the human placenta were studied using a single pass (open) in vitro perfusion model. The effects of change in sufentanil concentration (1-100 ng.ml-1) and change in fetal pH (range 7.4-6.8) on placental transfer were studied. Placental metabolism of sufentanil and the effects of maternal protein content (fresh human plasma, albumin 4%, Media 199) on placental transfer were also investigated utilizing a closed (recirculated) in vitro perfusion system. RESULTS: Sufentanil transfer was 2% at five minutes and plateaued at 12% by 45 min. The clearance index (CI = sufentanil clearance/antipyrine clearance) was 0.56 +/- 0.2 for maternal to fetal (MTF) and 0.44 +/- 0.2 in the fetal to maternal (FTM) directions (P = NS). The CI was 0.5 +/- 0.2 for 1 ng.ml-1 and 0.61 +/- 0.3 for 100 ng.ml-1 sufentanil concentration (P = N.S.). The placenta contained 7.1 +/- 2 and 9.8 +/- 3 ng.g-1 sufentanil following MTF and FTM perfusions for 90 min at 1 ng.ml-1. The placenta did not metabolize sufentanil. After one hour MTF washout, placental sufentanil content was 2.3 +/- .5 ng.g-1 with 0.08 ng.ml-1 sufentanil in the umbilical vein. Maternal plasma decreased MTF CI from 0.41 +/- 0.1 for albumin and 0.4 +/- 0.1 for Media 199 to 0.17 +/- .06 for plasma (P < 0.05). Decreasing fetal pH increased MTF CI from 0.57 +/- .13 at pH 7.4 to 1.6 +/- .4 at pH 6.8 (P < 0.05). CONCLUSION: Sufentanil crossed the placenta by passive diffusion and accumulated in placental tissue, which acted as a drug depot, slowing the initial transfer. Placental transfer was decreased by maternal plasma proteins, but not by albumin. Fetal acidosis increased placental transfer. Due to its low initial umbilical vein concentration, sufentanil may be the opioid of choice when delivery is imminent (< 45 min).

Acidosis↗
PubMed1997

Wound infiltration with liposomal bupivacaine prolongs analgesia in rats.

BACKGROUND: Wound infiltration with local anesthetics does not reliably produce satisfactory postoperative analgesia, and the dose of local anesthetic which may be safely administered is limited by the potential for systemic toxicity. This study evaluated the efficacy of a slow-release liposomal bupivacaine formulation on duration of wound analgesia. METHODS: Multilammelar liposomes containing bupivacaine were assessed using a rat paw wound model. Twenty-four hours after surgical incision, paw wounds determined to be hyperalgesic to graded force testing with von Frey hairs were infiltrated with 0.3 ml of 2% liposomal bupivacaine, 0.5% plain bupivacaine, saline, or "empty' (normal saline) liposomes (n = 6/group). The duration of analgesia was measured. The 0.5% plain concentration was chosen because, in preliminary experiments, larger doses were often fatal. Analgesia duration was compared using Mann-Whitney U test at P < 0.05. In other rats, plasma bupivacaine levels after wound infiltration with either 2% liposomal formulation or 0.5% plain formulation were assessed (n = 8/group). RESULTS: The mean duration of analgesia was 23 +/- 3 (SD) min for plain bupivacaine and 180 +/- 30 min for liposomal bupivacaine. No wound analgesia was detected in animals given normal saline or "empty' liposomes. Plasma bupivacaine levels tended to be lower after liposomal than plain bupivacaine. CONCLUSIONS: The 8-fold increase in duration of wound analgesia and the lower plasma levels seen with the liposomal formulation are explained by gradual drug release from the liposomal depot. These results may have important implications for achieving safe and effective analgesia with wound infiltration techniques in humans.

Analgesia↗
PubMed1996

Hemodynamic effects of intrathecal fentanyl in nonlaboring term parturients.

STUDY OBJECTIVE: To determine the effect of intrathecal fentanyl on maternal hemodynamics. DESIGN: Prospective. SETTING: Labor and delivery suite of a university medical center. PATIENTS: 23 ASA status I nonlaboring term parturients presenting for elective cesarean section. INTERVENTIONS: Patients were given either 1,200 ml lactated Ringer's Solution (Group 1, n = 12) or no intravenous (i.v.) fluid (Group 2, n = 11). A combined spinal-epidural technique was then performed. Fentanyl 25 micrograms was administered intrathecally through a 24-gauge Sprotte or 25-gauge Whitacre spinal needle. After completion of the hemodynamic study, a catheter was threaded into the epidural space for local anesthetic administration. MEASUREMENTS AND MAIN RESULTS: Baseline hemodynamic data [systolic (SBP), diastolic, and mean arterial pressure, heart rate, stroke volume, cardiac output, end-diastolic volume, and ejection fraction] were obtained in triplicate using noninvasive blood pressure monitoring and impedance cardiography. After administration of intrathecal fentanyl, hemodynamic measurements were recorded at 3-minute intervals for 30 minutes. These values were compared with baseline for both groups. Ten patients in each group completed the study. Intrathecal fentanyl administration did not result in any maternal hemodynamic changes in Group 1, and a few small statistically significant changes in Group 2. Measured SBP was always greater than 100 mmHg in all patients during the study. CONCLUSION: Intrathecal administration of fentanyl 25 micrograms in nonlaboring term parturients does not produce clinically important maternal hemodynamic changes.

Adult↗
PubMed1996

Spinal anesthesia by local anesthetics stimulates the enzyme protein kinase C and induces the expression of an immediate early oncogene, c-Fos.

To understand the biochemical mechanisms involved in spinal anesthesia, we measured protein kinase C (PKC) activity and expression of immediate early oncogene protein, c-Fos, in the spinal cord. Spinal anesthesia was induced in mice using intrathecal injection of either 10 microL procaine or tetracaine (0.067 M/approximately 2%). Control groups were treated with either saline or ethanol. Animals were killed at 1, 5, and 15 min after the injection and the caudal 3 cm of the spinal cord was processed for biochemical analysis. PKC activity was measured by the transfer of a phosphate group from [gamma-32P]adenosine 5'-triphosphate to the threonine group on a synthetic peptide specific for PKC. Western blot analysis was used to detect changes in c-Fos protein expression. When compared to saline-treated controls, PKC activity was increased significantly (P < 0.0005) in procaine- and tetracaine-treated groups whereas ethanol decreased PKC activity. The less lipid-soluble procaine produced a larger increase in PKC activity than did the more lipid-soluble tetracaine. Moreover, parallel to the effect on PKC activity, procaine was more potent than tetracaine as a c-Fos inducer. These results implicate some role for a PKC- and c-Fos-dependent pathway in the mechanism of spinal anesthesia. However, these results also demonstrate a lack of correlation between an increase in PKC levels and either potency or lipid solubility of the anesthetics. The increased PKC activity may not be the sole mechanism for spinal anesthesia. These data on the effects of local anesthetics on PKC activity and c-Fos in vivo are of relevance for studies aimed at delineating the biochemical basis of spinal and epidural anesthesia.

Anesthesia, Spinal↗
PubMed1995

Hot plate versus tail flick: evaluation of acute tolerance to continuous morphine infusion in the rat model.

The development of tolerance to continuous morphine infusion (2, 4 and 6 mg x kg(-1) x hr(-1) was assessed in rats using two different methods for evaluation of nociception, tail flick (TF) and hot plate (HP). The influence of repeated testing on nociception was evaluated using two regimens; series 1 was tested repeatedly 1, 2, 4, 6, and 8 hr after initiating the morphine infusion and series 2 was tested only twice, at maximum morphine effect and at 8 hr. Both, TF and HP showed pain threshold elevation after the morphine administration of 4 or 6 mg x kg(-1) x hr(-1), which reached a maximum at 2 hr after the start of the infusion. HP: reduction of the effect was found in group 4 mg x kg(-1) x hr(-1) in the series subjected to repeated testing; group 6 mg x kg(-1) x hr(-1) showed reduced effect in both sides. TF: the response latencies did not show reduction at 8 hr. Since TF is predominantly a spinal response and HP is predominantly supraspinal, the results suggest that tolerance during the first 8 hr of morphine infusion develops mainly at supraspinal level.

Analgesics, Opioid↗
PubMed1995

Intrathecal administration of liposomal morphine in a mouse model.

The authors determined the duration of analgesia, toxicity, and neuraxial distribution of liposomal morphine after intrathecal administration in the mouse. Analgesic duration was determined using the tail-flick test after intrathecal injection of 12.5, 25, or 50 micrograms of plain or liposomal morphine (n = 6 mice/dose/formulation). Toxicity of the formulations was compared by estimating LD50. Neuraxial morphine distribution was determined after 20 micrograms of plain or liposomal morphine. The excised spinal cord and brain were divided into five segments at 1 min, and at 1, 4, and 8 h after injection for both formulations. In addition, for the liposomal morphine, similar sections were obtained at 24 h (n = 6 mice/formulation/time point). Segmental morphine concentration was quantified using radioimmunoassay. Liposomal encapsulation significantly prolonged duration of analgesia for the 25-micrograms (13.4 +/- 1.64 [SE] vs 4.1 +/- 0.5 h) and 50-micrograms doses (16.8 +/- 4.0 vs 4.6 +/- 1.0 h). The estimated LD50 was 200 (confidence interval 151-257 micrograms) for plain morphine, but was not determinable for the liposomal formulation, since no deaths occurred at the largest dose level which could be tested (371 micrograms). For plain morphine, the drug was not confined to a specific neuraxial segment, and segmental levels declined rapidly. After liposomal morphine, the most morphine was concentrated and persisted in the low spinal cord segment at each time interval. These results show that a single dose of liposomal morphine produces prolonged analgesia with decreased toxicity compared to the plain formulation.

Animals↗
PubMed1994

Duration of spinal anaesthesia is determined by the partition coefficient of local anaesthetic.

We have compared the duration of motor block produced by four local anaesthetics administered into a chronically implanted subarachnoid catheter in rabbits. Each group (n = 6) received four different doses of amethocaine, bupivacaine, lignocaine or procaine, and the duration of the resulting motor block was assessed. Dose-response curves were plotted for each drug. As a measure of activity of the anaesthetics, we used the dose of each drug required to produce block of 60-min duration (D60 min) and the correlation between D60 min and different drug properties was examined. An inverse linear correlation (r = 0.995; P < 0.01) was observed between log D60 min and the log of the partition coefficient of the local anaesthetics. No correlation was found between the effect and degree of protein binding, pKa or molecular weight. These results suggest that, in spinal anaesthesia, the partition coefficient could be used as a predictor of the duration of anaesthetic action.

Anesthesia, Spinal↗
PubMed1994

The partition coefficient as a predictor of local anesthetic potency for spinal anesthesia: evaluation of five local anesthetics in a mouse model.

Local anesthetic partition coefficients correlate with drug potencies in vitro, but in vivo data have not always complimented in vitro results. Despite extensive studies on intrathecal anesthetic action, whether there is correlation between the partition coefficient and local anesthetic potency has not been addressed. Mice (n = 150) were randomly allocated into 15 groups. Intrathecal injections of etidocaine (E), tetracaine (T), bupivacaine (B), lidocaine (L), or procaine (P) were administered and analgetic effect was measured using tail-flick (TF) test. Concentration-response regressions were constructed for each drug; EC50 values were calculated and compared at 95% confidence intervals. The EC50 values between E (0.017%), T (0.019%), and B (0.012%) were not significantly variant. The EC50 of L (0.098%) and P (0.229%) were significantly different from each other and from E, T, and B. The EC50 values were converted to ED50 in nmols. Relative anesthetic potency, defined as the inverse value of ED50 of drug was 23:16:15:2.4:1 for B, E, T, L, and P, respectively. ED50 showed high correlation (R = 0.978) with partition coefficients of local anesthetics. This study implies that the partition coefficient is a predictor of intrathecal local anesthetic potency. We suggest that the mouse model is reliable for evaluation of intrathecal local anesthetic action.

Anesthesia, Spinal↗
PubMed1994

Prolonged analgesia and decreased toxicity with liposomal morphine in a mouse model.

Inadequate control of postoperative pain remains a major clinical problem. A reliable method of providing long-lasting postoperative analgesia with a single dose would be very useful. We synthesized a liposomal morphine formulation and compared it to free morphine with regard to duration of analgesia in the mouse. Analgesia was assessed after intraperitoneal injection using the tail-flick test. The systemic toxicity after administration of liposomal and free morphine was compared. The release rate of morphine from liposomes in vitro was also evaluated. The lethal intraperitoneal dose of free morphine in 50% of mice (LD50) was 400 mg/kg. The maximum safe (non-lethal) dose of free morphine was 130 mg/kg. The highest dose of liposomal morphine administered (1650 mg/kg) did not cause death in any animal. Duration of analgesia was significantly prolonged with the highest dose of liposomal morphine (21.5 +/- 5.3 h) compared to the maximum safe dose of free morphine (3.7 +/- 0.75 h), P < 0.01. In vitro experiments showed a slow release rate of morphine from the liposome depot. Prolonged analgesia and decreased systemic toxicity for liposomal morphine are explained by sustained release of morphine from the liposomal depot. These results suggest that liposomal narcotic formulations may provide prolonged analgesia with single-dose administration.

Analgesia↗
PubMed1994

Transfer and uptake of alfentanil in the human placenta during in vitro perfusion.

Alfentanil, a short-acting lipophilic opioid, is used for labor analgesia and cesarean section and may cause neonatal depression. However, direct placental alfentanil transfer has not been studied. We measured placental alfentanil transfer and uptake during in vitro perfusion. Placenta lobules from healthy parturients were perfused with biophase at pH 7.4, 95%:5% O2:CO2. Maternal to fetal (MTF, n = 10) and fetal to maternal (FTM, n = 10) transfer were examined during perfusion with alfentanil 10 ng/mL, antipyrine, and creatinine for 1 h. Thereafter, both MTF and FTM placentas were assayed for alfentanil content (n = 3), or perfused with biophase for 1 h to determine drug washout and then assayed for alfentanil content (n = 3). After the 1 h washout, the remaining MTF placentas (n = 4) were then perfused MTF with high-dose alfentanil 1000 ng/mL to assess saturability of placental transfer. The remaining FTM placentas (n = 4) were then perfused with alfentanil 10 ng/mL in the MTF direction to verify that the same alfentanil transfer characteristics found between placentas were valid when the direction of drug transfer was reversed in the same placenta. Alfentanil was rapidly transferred (< 5 min) across the placenta both MTF and FTM. During MTF transfer, fetal effluent reached a plateau at 2.2 ng/mL between 35 and 55 min, and was unmeasurable 30 min into washout. During FTM transfer, maternal effluent reached a plateau at 1.9 ng/mL at 25-45 min, and was absent after 20-45 min of washout.(ABSTRACT TRUNCATED AT 250 WORDS)

Alfentanil↗
PubMed1994

Strategies for prenatal HLA typing for potential cord blood donor evaluation.

The reasons for prenatal HLA typing for potential cord blood stem cell donor evaluation are reviewed and the strategies for doing so are summarized. Cultured fetal cells are class I HLA typed by modified serological techniques. When indicated, the fetal cells are also class II HLA typed by one or another DNA typing method. The same procedures can be used for the prenatal identification of a potential donor for an affected fetus.

Blood Donors↗