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Biomedical subjects

J J Vallner

Publications and source records attributed to J J Vallner.

47 records · Page 3Linked to original sources
PubMed1975

Indomethacin release from silicone rubber: a suggested method for continuous inhibition of prostaglandin synthesis.

Indomethacin was vulcanized in dimethylpolysiloxane, an inert silicone suitable for tissue implantation. The drug is released from this polymer matrix gradually in amounts that can inhibit endogenous prostaglandin synthesis. The method is simple, rapid and inexpensive and eliminates repetitive administration in studies where prolonged inhibition of prostaglandin synthesis is desired.

Delayed-Action Preparations↗
PubMedDate not supplied

Blood levels following multiple oral dosing of chlorpheniramine conventional and controlled release preparations.

An examination of steady-state performance of chlorpheniramine conventional versus controlled release products was conducted using 15 male subjects in a 3-way crossover study with a 2-week washout period between studies. The study was designed to determine if chlorpheniramine formulations provide consistent pharmacokinetic performance between individual units upon going from single dose to multiple dose therapy. In addition, the validity of predicting steady-state levels for these kinds of products using only single oral dose data was examined. The dosage forms evaluated were a conventional 4 mg tablet, and 8 mg barrier coated-bead capsule, and an 8 mg repeat action tablet. Multiple doses of each product were orally administered to each subject for 6 days prior to the study day to achieve steady-state levels and on the actual study day. Serum samples were collected at specific time intervals on the study day, and chlorpheniramine levels assayed by HPLC. Pharmacokinetic analysis was based on a two-compartment open model. The mean plasma elimination half-lives of the various dosage forms were in the range 24.5-25.4 h. There was no rapid release of drug from the controlled release products nor did they have drug release problems during the dosing interval. Good agreement was obtained between predicted average drug concentration at steady-state and drug concentration actually present for all the formulations studied. Based upon comparative examination of AUC, Cmax, and fraction of dose absorbed data, the controlled release products administered every 12 h were comparable in performance to a conventional release tablet administered every 6 h. Since the half-life of chlorpheniramine is approximately 1 day, therapeutic management may possibly be gained with dosing the patient once daily with a controlled release product or twice daily with a conventional tablet.

Adolescent↗
PubMedDate not supplied

Pharmacodynamics of acute intranasal administration of verapamil: comparison with i.v. and oral administration.

The present study was conducted in order to examine the intranasal administration of verapamil and compare this route to oral and intravenous administration in a 3 way crossover protocol in five dogs. Unanesthetized, adult mongrel dogs were given verapamil intravenously (0.5 mg/kg), orally (2.5 mg/kg) and intranasally (0.75 mg/kg) with at least a 3-4 day washout period between each administration. Blood samples were collected over a 10 hour period and analyzed for verapamil using HPLC with fluorescence detection. A lead II ECG was monitored to determine the effects of verapamil on heart rate and P-R interval. Following intravenous administration, verapamil was distributed according to a two compartment model. Bioavailability (corrected for dose and elimination rate constant) following intranasal administration (36% +/- 7%) was approximately 3 fold that after oral administration (13% +/- 3%). Absorption from the nasal cavity appeared instantaneous compared to an absorption half-life of 50 +/- 6 min after oral administration. All three routes of administration resulted in significant increases in heart rate and increases in the P-R interval. Maximal P-R interval prolongation occurred after peak plasma concentrations of verapamil. The results of this study suggest that the intranasal route is a viable alternative route of administration for verapamil.

Administration, Intranasal↗
PubMedDate not supplied

Pharmacokinetics of tiazofurin in dogs.

The pharmacokinetics of total and free tiazofurin, an antineoplastic agent, was studied in healthy mongrel dogs following intravenous and oral administration of the drug. The free fraction of tiazofurin was obtained from plasma by an ultrafiltration technique using a micropartition system. Total and free tiazofurin levels were determined by a sensitive high performance liquid chromatographic method. The percentage of tiazofurin bound to plasma proteins remained constant at approximately 15 per cent following administration to healthy mongrel dogs. The mean pharmacokinetic parameters of elimination rate constant (K), effective half-life (t 1/2), mean residence time (MRT) and the time to reach peak plasma level (tmax--after oral administration) were 0.32 +/- 0.04 h-1, 2.24 +/- 0.25 h, 3.23 +/- 0.36 h, and 1.78 +/- 0.50 h, respectively. The apparent volume of distribution at steady state was 0.98 +/- 0.30 1 kg-1 and the plasma clearance was 5.24 +/- 2.39 ml min-1 kg-1. About 90 per cent of tiazofurin was absorbed following oral administration. The pharmacokinetic parameters did not differ significantly between the total and free drug levels, indicating that the pharmacokinetics of total tiazofurin levels reflect those of the free tiazofurin in plasma.

Animals↗
PubMedDate not supplied

Intraoperative serum concentrations of cefazolin and cefoxitin administered preoperatively at different times.

The effect of administration time on the serum concentrations of cefazolin and cefoxitin achieved during surgery was studied. Patients about to undergo elective surgery were randomly selected to receive one of four antibiotic prophylaxis regimens. Two of the regimens consisted of cefazolin 20 mg/kg i.v. (as the sodium salt) administered either "on call" to the operating room or with anesthesia in the operating room. The other two regimens were identical except that cefoxitin 30 mg/kg i.v. (as the sodium salt) was substituted for cefazolin. Intraoperative blood samples for analysis of serum concentrations were obtained at the time of surgical incision, one hour after incision, and at wound closure. Forty patients completed the study (10 patients received each treatment). Mean projected cefazolin concentrations at the time of incision and at wound closure for both two-hour and three-hour operations were significantly higher after administration with anesthesia than after "on-call" administration. For cefoxitin, differences in projected concentrations for "on-call" administration versus administration with anesthesia were significant at the time of incision and at wound closure in a two-hour operation. At times corresponding to initial incision, projected free-cefoxitin concentrations were higher than those of cefazolin; however, projected free-cefazolin concentrations were higher than free-cefoxitin concentrations at wound closure for two-hour and three-hour operations. To ensure that antibiotic is present in serum throughout a two- or three-hour surgical procedure, cefoxitin should probably be administered at the induction of anesthesia. Cefazolin administered "on call" appears to be acceptable for maintaining serum concentrations throughout surgery of this duration.

Adolescent↗