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Biomedical subjects

T H Joyce

Publications and source records attributed to T H Joyce.

31 records · Page 2Linked to original sources
PubMed1983

Continuous perineural infusion of bupivacaine for prolonged analgesia: pharmacokinetic considerations.

The pharmacokinetic parameters for 50 patients undergoing continuous extravascular perineural bupivacaine infusions for the treatment of their chronic pain were studied. The total plasma clearance (CL), volume of distribution (Vz), and elimination rate (lambda z) were estimated from two blood samples. These parameters were compared to values obtained from the actual mono-exponential decay curve at the termination of infusion. Estimated and actual pharmacokinetic parameters were found to be in excellent agreement. No evidence of accumulation was seen even after 5 days of continuous infusion. Steady states (Css) were found to be independent of the infusion site. This study demonstrates a wide margin of safety during continuous perineural bupivacaine infusions at dosages used in our study, e.g., up to 30 mg/h in normal patients. Such patients do not require determination of serum bupivacaine concentration to monitor the changes in dosages necessary for adequate clinical effect. On the other hand, in patients with renal or hepatic dysfunction, altered clearance rates are expected. In such patients, monitoring of serum bupivacaine concentrations is necessary to determine the range of dosages available for adjustment to provide adequate clinical effect and prevent systemic toxicity. This study demonstrates that two blood samples drawn at 3-5 h after the start of infusion and at steady state are sufficient to accurately determine the clearance rate for a patient. Safe management is then possible using this clearance to calculate the range of dosages permissible for that patient during continuous perineural infusion. Steady-state concentrations estimated from clearances were found to be in excellent agreement with the steady-state concentrations actually measured for a given infusion rate.

Brachial Plexus↗
PubMed1977

Clinical pharmacokinetics of lorazepam. II. Intramuscular injection.

A single dose of 4 mg of lorazepam was injected into the deltoid muscles of six healthy male volunteers. Multiple venous blood samples were drawn during 48 hr after the dose and all urine was collected for 24 hr after the dose. Concentrations of lorazepam and its major metabolite, lorazepam glucuronide, were determined by electron-capture gas-liquid chromatography. Lorazepam was rapidly absorbed from the injection site, reaching peak concentrations within 3 hr. Mean pharmacokinetic pamrameters for unchanged lorazepam were: apparent absorption half-life: 21.2 min; elimination half-life: 13.6 hr; volume of distribution: 0.9 L/kg; total clearance: 58.2 ml/min. Lorazepam glucuronide rapidly appeared in plasma, reached peak concentrations within 12 hr of the dose, then was eliminated approximately in parallel with the parent drug. Within 24 hr a mean of 47.6% of the dose was recovered in the urine as lorazepam glucuronide and less than 0.5% was recovered as unchanged lorazepam.

Adult↗
PubMedDate not supplied

A reevaluation of the association between instrument delivery and epidural analgesia.

BACKGROUND AND OBJECTIVES: Over 100 papers in the medical literature suggest pro or con that epidural analgesia is associated with an increase in the incidence of instrument delivery. This two-component study was performed to evaluate the influence of epidural labor analgesia on the incidence of instrument delivery. METHODS: Component 1 was a retrospective analysis of the medical records of 14,804 mothers having a vaginal delivery before and after implementation of an active epidural service. Component 2 was a case control study designed to determine factors, in addition to epidural analgesia, associated with an increase in instrument delivery. In component 2 11 factors describing maternal, fetal, anesthetic, and obstetric factors were analyzed for each of 609 consecutive patients having an instrument delivery and 246 controls having a spontaneous vaginal delivery. RESULTS: In component 1, despite a tenfold increase in the use of epidural analgesia, there was a similar association between epidural use and instrument delivery in both time periods. Additionally, the epidural-forceps association was twice as strong for parous patients as for nulliparous patients (odds-ratios 9.74 and 4.52, respectively). In component 2, five factors were significantly (P > .0001) associated with instrument delivery conclusions. CONCLUSIONS: While epidural analgesia was one factor, the others were gestational age > 41 weeks, a second stage of labor > 2 hours, an occiput posterior or transverse fetal position, and previous cesarean section. These four factors are individually and independently associated with an increase in the incidence of instrument delivery independent of epidural use.

Adolescent↗
PubMedDate not supplied

Efficacy of transnasal butorphanol tartrate in postepisiotomy pain: a model to assess analgesia.

Butorphanol tartrate, a synthetically derived opioid agonist-antagonist analgesic, was tested in a large group of postpartum women (N = 76) to assess the safety and analgesic efficacy of a recently approved transnasal preparation of this drug in the relief of postepisiotomy pain. The safety and efficacy of intravenous and intramuscular administration of butorphanol tartrate has been established over 14 years of clinical use. The new nasal spray dosage form offers a similar degree of efficacy with a rapid onset of action. Compared with the injectables and other drugs in this class, transnasal butorphanol has a longer duration of action (4 to 5 hours). In this double-blind, parallel-group, dose-response study, 76 female patients ages 17 to 37 years with moderate to severe postepisiotomy pain were randomly assigned to receive a single dose of transnasal butorphanol (0.25, 0.5, 1, or 2 mg) or placebo. The patients were evaluated for 6 hours. The results of the study indicate that the 1-mg and 2-mg doses were associated with greater efficacy compared with placebo using several markers for efficacy, including the pain relief score and time to remedication. The drug was well tolerated, dizziness and drowsiness being the most frequently reported adverse effects. Adverse effects appeared to be dose related.

Administration, Intranasal↗