[Reconsideration of the indications for unicompartmental knee arthroplasty]

Unicompartmental knee arthroplasty (UKA), a procedure that has gradually emerged in recent years, is considered an effective treatment for resolving knee pain and restoring good function due to its significant clinical advantages. In the 1980s, Kozinn and Scott proposed the classic indications as selection criteria to identify ideal candidates for UKA. However, as treatment concepts, surgical instruments, surgical techniques, and prosthesis designs for this disease have improved, these indications proposed more than 30 years ago appear too limited, leading to some limitations in the widespread use of UKA. Specifically, surgeons have offered new perspectives on issues related to obesity, age, patellofemoral arthritis, severe varus deformity of the knee, anterior cruciate ligament deficiency, flexion contracture, failed high tibial osteotomy and post-traumatic arthritis. For this reason, this article will briefly discuss modern perspectives involving the indications for UKA based on current evidence with the aim of providing a reference for the reader.

[Lateral unicompartmental knee arthroplasty: challenges and hopes]

There is a low prevalence of osteoarthritis in the lateral compartment of the knee, but the overall number of domestic patients is large, and lateral unicompartmental arthroplasty (UKA) has good prospects.The unique anatomical structure and kinematic characteristics of the lateral compartment make the surgical operation more challenging.Traditional UKA patients have a high incidence of lower limb mal-alignment and poor prosthetic position, which leads to limit of their promotion and application.In recent years, with the development of treatment concepts, surgical techniques and materials, the survival time of UKA prosthesis has been continuously extended, and the clinical effect has been continuously optimized.Strictly grasp the surgical indications in radiology, anatomy and clinical manifestations, familiarize with the lateral compartment anatomy and biomechanical features, and master the technical details are the prerequisites and guarantees for the success of the lateral UKA.With the advancement of technology, minimal invasion, precision and individuation should be the goal pursued for lateral UKA surgery.

A summary of recent findings on birth outcomes and developmental effects of prenatal ETS, PAH, and pesticide exposures

Inner-city minority populations are high-risk groups for adverse birth outcomes and also more likely to be exposed to environmental contaminants, including environmental tobacco smoke (ETS), benzo[a]pyrene B[a]P, other ambient polycyclic aromatic hydrocarbons (global PAHs), and residential pesticides. The Columbia Center for Children's Environmental Health (CCCEH) is conducting a prospective cohort study of 700 northern Manhattan pregnant women and newborns to examine the effects of prenatal exposure to these common toxicants on fetal growth, early neurodevelopment, and respiratory health. This paper summarizes results of three published studies demonstrating the effects of prenatal ETS, PAH, and pesticides on birth outcomes and/or neurocognitive development [Perera FP, Rauh V, Whyatt RM, Tsai WY, Bernert JT, Tu YH, et al. Molecular evidence of an interaction between prenatal environment exposures on birth outcomes in a multiethnic population. Environ Health Perspect 2004;12:630-62; Rauh VA, Whyatt RM, Garfinkel R, Andrews H, Hoepner L, Reyes A, et al. Developmental effects of exposure to environmental tobacco smoke and material hardship among inner-city children. Neurotoxicol Teratol 2004;26:373-85; Whyatt RM, Rauh V, Barr DB, Camann DE, Andrews HF, Garfinkel R, et al. Prenatal insecticide exposures, birth weight and length among an urban minority cohort. Environ Health Perspect, in press]. To evaluate the effects of prenatal exposure to ETS, PAHs, and pesticides, researchers analyzed questionnaire data, cord blood plasma (including biomarkers of ETS and pesticide exposure), and B[a]P-DNA adducts (a molecular dosimeter of PAHs). Self-reported ETS was associated with decreased head circumference (P = 0.04), and there was a significant interaction between ETS and adducts such that combined exposure had a significant multiplicative effect on birth weight (P = 0.04) and head circumference (P = 0.01) after adjusting for confounders. A second analysis examined the neurotoxic effects of prenatal ETS exposure and postpartum material hardship (unmet basic needs in the areas of food, housing, and clothing) on 2-year cognitive development. Both exposures depressed cognitive development (P < 0.05), and there was a significant interaction such that children with exposure to both ETS and material hardship exhibited the greatest cognitive deficit (7.1 points). A third analysis found that cord chlorpyrifos, and a combined measure of cord chlorpyrifos, diazinon, and propoxur-metabolite, were inversely associated with birth weight and/or length (P < 0.05). These results underscore the importance of policies that reduce exposure to ETS, air pollution, and pesticides with potentially adverse effects on fetal growth and child neurodevelopment.

beta-Scruin, a homologue of the actin crosslinking protein scruin, is localized to the acrosomal vesicle of Limulus sperm

Scruin (alpha-scruin) is an actin bundling protein found in the acrosomal process of Limulus polyhemus sperm. We have cloned and sequenced a second scruin isoform from Limulus, beta-scruin, that is 67% identical to alpha-scruin. Northern and Southern analyses confirm that beta-scruin and alpha-scruin are encoded by distinct genes. The sequence of beta-scruin, like alpha-scruin, is organized into N- and C-terminal superbarrel domains that are characterized by a six-fold repeat of a 50 residue motif. Western analysis using rabbit polyclonal antisera specific for alpha- and beta-scruin indicate that beta-scruin, like alpha-scruin, is found in Limulus sperm but not blood or muscle. Both immunofluorescence microscopy and immunogold-EM localize beta-scruin within the acrosomal vesicle at the anterior of sperm but not in the acrosomal process. The function of beta-scruin in this membrane-bounded compartment that is devoid of actin is unknown. However, the location of beta-scruin together with the fact that it contains two putative beta-superbarrel structural folds, which are known to be catalytic domains in a number of proteins, suggests it may have a possible enzymatic role.

Two microtubule-associated proteins required for anaphase spindle movement in Saccharomyces cerevisiae

In many eucaryotic cells, the midzone of the mitotic spindle forms a distinct structure containing a specific set of proteins. We have isolated ASE1, a gene encoding a component of the Saccharomyces cerevisiae spindle midzone. Strains lacking both ASE1 and BIK1, which encodes an S. cerevisiae microtubule-associated protein, are inviable. The analysis of the phenotype of a bik1 ase1 conditional double mutant suggests that BIK1 and ASE1 are not required for the assembly of a bipolar spindle, but are essential for anaphase spindle elongation. The steady-state levels of Ase1p are regulated in a manner that is consistent with a function during anaphase: they are low in G1, accumulate to maximal levels after S phase and then drop as cells exit mitosis. Components of the spindle midzone may therefore be required in vivo for anaphase spindle movement. Additionally, anaphase spindle movement may depend on a dedicated set of genes whose expression is induced at G2/M.

Characterization of caveolin-rich membrane domains isolated from an endothelial-rich source: implications for human disease

Caveolae are 50-100-nm membrane microdomains that represent a subcompartment of the plasma membrane. Previous morphological studies have implicated caveolae in (a) the transcytosis of macromolecules (including LDL and modified LDLs) across capillary endothelial cells, (b) the uptake of small molecules via a process termed potocytosis involving GPI-linked receptor molecules and an unknown anion transport protein, (c) interactions with the actin-based cytoskeleton, and (d) the compartmentalization of certain signaling molecules, including G-protein coupled receptors. Caveolin, a 22-kD integral membrane protein, is an important structural component of caveolae that was first identified as a major v-Src substrate in Rous sarcoma virus transformed cells. This finding initially suggested a relationship between caveolin, transmembrane signaling, and cellular transformation. We have recently developed a procedure for isolating caveolin-rich membrane domains from cultured cells. To facilitate biochemical manipulations, we have applied this procedure to lung tissue--an endothelial and caveolin-rich source-allowing large scale preparation of these complexes. These membrane domains retain approximately 85% of caveolin and approximately 55% of a GPI-linked marker protein, while they exclude > or = 98% of integral plasma membrane protein markers and > or = 99.6% of other organelle-specific membrane markers tested. Characterization of these complexes by micro-sequencing and immuno-blotting reveals known receptors for modified forms of LDL (scavenger receptors: CD 36 and RAGE), multiple GPI-linked proteins, an anion transporter (plasma membrane porin), cytoskeletal elements, and cytoplasmic signaling molecules--including Src-like kinases, hetero-trimeric G-proteins, and three members of the Rap family of small GTPases (Rap 1--the Ras tumor suppressor protein, Rap 2, and TC21). At least a fraction of the actin in these complexes appeared monomeric (G-actin), suggesting that these domains could represent membrane bound sites for microfilament nucleation/assembly during signaling. Given that the majority of these proteins are known molecules, our current studies provide a systematic basis for evaluating these interactions in vivo.

Identification of I-plastin, a human fimbrin isoform expressed in intestine and kidney

The complete cDNA sequence of human intestine-specific plastin (I-plastin) was determined from a clone derived by PCR. It consists of a 97-bp 5' untranslated region, a 1,887-bp coding region, and a 1,655-bp 3' untranslated region. The coding region predicts a 629-residue polypeptide whose sequence displays 86, 75, and 73% identities with chicken intestine fimbrin, human T-plastin, and human L-plastin, respectively. Recombinant I-plastin cross-linked actin filaments into bundles in the absence but not in the presence of calcium. The I-plastin gene was mapped by PCR to human chromosome 3; the L- and T-plastin genes were previously mapped to chromosomes 13 and X, respectively. I-plastin mRNA was detected in the small intestine, colon, and kidneys; relatively lower levels of expression were detected in the lungs and stomach. In contrast, L-plastin expression was restricted to the spleen and other lymph node-containing organs, while T-plastin was expressed in a variety of organs, including muscle, brain, uterus, and esophagus. In contrast to the situation for the intestine, high levels of L- and T-plastin mRNAs were detected in Caco-2, a human colon-derived cell line. Immunofluorescence microscopy detected I-plastin in the brush border of the small intestine and colon. These results identify I-plastin as the human homolog of chicken intestine fimbrin and as a third plastin isoform in humans.

Iontophoresis of hydrocortisone across hairless mouse skin: investigation of skin alteration

The effects of hydration, sodium dodecyl sulfate (SDS), and electric current on the permeability of hairless mouse skin was examined in vitro with a neutral solute, hydrocortisone, as a permeant. The study was carried out by pretreating the skin with (1) normal saline, (2) 0.06% SDS in 0.3% NaCl, (3) normal saline plus 0.5 mA anodic current, and (4) 0.06% SDS in 0.3% NaCl plus 0.5 mA anodic current for 8 h. The pretreated skin was then immediately used for passive or anodic transport of hydrocortisone. Results show that pretreatment of skin with either normal saline or 0.06% SDS resulted in a slightly increased passive penetration of hydrocortisone with a prolonged lag time, but did not significantly change the anodic transport of hydrocortisone. There was no significant difference between normal saline pretreatment and 0.06% SDS pretreatment, indicating that 0.06% SDS did not irreversibly alter the permeability of skin other than its hydration effect. Pretreatment of skin with current, and especially with current combined with 0.06% SDS, yielded a significant increase in both passive and anodic transport of hydrocortisone with reduced lag time, indicating that alteration of the skin structure had occurred. The reversibility of this alteration depends on the duration of exposure of the skin to the electric field. Short-term exposure (< 2 h) does not appear to change the permeability of skin in any significant way; long-term exposure may lead to slowly reversible or irreversible skin alteration.

Stability of fentanyl citrate and bupivacaine hydrochloride in portable pump reservoirs

The stability of fentanyl citrate and bupivacaine hydrochloride in an admixture with 0.9% sodium chloride injection in portable pump reservoirs with or without overwraps was investigated. Twelve 100-mL samples containing fentanyl 20 micrograms/mL and bupivacaine hydrochloride 1250 micrograms/mL were placed in the plastic drug reservoirs, and 1-mL quantities were withdrawn immediately after preparation and at intervals during 30 days of storage. Six reservoirs were refrigerated (3 degrees C) and six stored at room temperature (23 degrees C); three at each temperature were placed in overwraps. All samples were observed for precipitation and for change in color or pH and were analyzed for drug concentration by high-performance liquid chromatography. No precipitation or change in color or pH was observed during the 30-day storage period. No loss of fentanyl or bupivacaine was detected in either the wrapped or the unwrapped samples. Fentanyl citrate and bupivacaine hydrochloride in 0.9% sodium chloride injection appear to be compatible, and admixtures containing the two drugs at the concentrations studied can be stored without overwraps for up to 30 days at refrigerated or room temperature without any significant loss of potency.

Stability of fentanyl citrate in 0.9% sodium chloride solution in portable infusion pumps

The stability of fentanyl citrate diluted with 0.9% sodium chloride injection for use in portable infusion pumps was studied. The commercially available injection containing 50 micrograms of fentanyl per milliliter was diluted to a concentration of 20 micrograms/mL. Twelve 100-mL portions of the dilute solution were placed in polyvinyl chloride infusion pump drug reservoirs; six were stored at 3 degrees C and six at 23 degrees C; three at each temperature were overwrapped with polypropylene-Mylar. Initially and after 5, 10, 20, and 30 days of storage, 1-mL samples were taken from each reservoir, inspected for color change and precipitation, and assayed for fentanyl concentration by high-performance liquid chromatography. Initially and on day 30, pH of the samples was checked. No precipitation or change in color or pH was observed. No substantial decrease in fentanyl concentration was found in either the wrapped or unwrapped samples at either temperature, although concentrations on day 30 in the samples at 23 degrees C were slightly lower than those at 3 degrees C. Under the conditions studied, fentanyl citrate solutions containing 20 micrograms of fentanyl per milliliter can be stored for 30 days in polyvinyl chloride reservoirs for portable infusion pumps.

Effect of pH on the equilibrium dialysis of phenytoin suspension with and without enteral feeding formula

Significant decreases have been reported in phenytoin absorption when the suspension is combined with continuous enteral feedings. Several theories for this interaction have been proposed including binding of phenytoin to the protein constituents of the enteral formula, phenytoin binding to the calcium in the enteral formula, and inadequate dissolution of the suspension when delivered with the enteral formula due to the high pKa of phenytoin and the acidic nature of the enteral formula. We therefore evaluated the effects of pH levels 2.0, 3.5, 6.0, and 8.0 on the interaction of phenytoin suspension with enteral formula (Osmolite) with equilibrium dialysis using a Spectra/Por 1 (MWCO 6000-8000) molecularporous dialysis membrane. Phenytoin concentrations in the dialysis membrane (internal phase) mimicked the expected stomach concentrations of a 100-mg dose administered in an adult stomach containing 200 ml of gastric fluid. External phase buffers were sampled at 0.5, 1.0, 2.0, 4.0, 8.0, 12.0, and 24.0 hr after the start of the dialysis. The phenytoin concentrations in the external phase were compared between buffer alone or buffer combined with enteral formula at the same pH and time intervals. With pH 2.0 and 3.5 the enteral formula formed an aggregate with suspension whereas no aggregate was formed with pH 6.0 and 8.0. The phenytoin concentrations with pH 2.0 were 26% to 44% lower and with pH 3.5 were 11.5 to 27% lower when phenytoin suspension was combined with enteral solution. However, at 24 hr there was no difference between the two conditions with both pH 2.0 and 3.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery of phenytoin suspension after in vitro administration through percutaneous endoscopic gastrostomy Pezzer catheters

Various methods of administering phenytoin suspension through a percutaneous endoscopic gastrostomy (PEG) Pezzer catheter were evaluated in vitro to determine which method resulted in the most complete recovery of phenytoin. To determine the effect of temperature on phenytoin recovery, 12 mL of phenytoin suspension (Dilantin-125, 125 mg/5 mL) was administered through three separate 35.5-cm 20 French latex PEG Pezzer catheters under each of three temperature conditions (suspension 11.8 degrees C and catheter 22 degrees C, suspension and catheter 22 degrees C, and suspension 22 degrees C and catheter 37 degrees C). To determine the effect of the administration method, 12-mL aliquots of phenytoin suspension were injected into the catheter by seven methods that varied with respect to catheter temperature, dilution of suspension, and irrigation of catheter. Each method was tested in triplicate, and samples were assayed by high-performance liquid chromatography. Varying the temperature of the catheter or suspension had little effect on the recovery of phenytoin. There was no appreciable loss of phenytoin when the suspension was undiluted, regardless of whether the catheter was irrigated. The greatest losses were seen when the suspension was diluted before administration. Irrigation also caused a decrease in recovery, but to a lesser extent than dilution. Until the effects of administering multiple doses of phenytoin through PEG Pezzer catheters are investigated, phenytoin suspension should not be diluted before administration because of decreased recovery and increased administration time.

Uptake of trimethoprim and metronidazole in the seminal vesicle: experimental study

A rat model for determining drug levels in the seminal vesicle was developed. In separate studies, trimethoprim and metronidazole were injected intravenously into rats and assays of seminal vesicle, plasma, and prostate performed. Drug levels were detected early in both the seminal vesicle and prostate. This appears to be the first study to report drug levels in the seminal vesicle. Metronidazole levels in the seminal vesicle were very low and short lived.

Nefopam hydrochloride degradation kinetics in solution

A stability-indicating reversed-phase high performance liquid chromatographic method was developed for the detection of nefopam hydrochloride and its degradation products under accelerated degradation conditions. The degradation kinetics of nefopam hydrochloride in aqueous solutions over a pH range of 1.18 to 9.94 at 90 +/- 0.2 degrees C was studied. The degradation of nefopam hydrochloride was found to follow apparent first-order kinetics. The pH-rate profile shows that maximum stability of nefopam hydrochloride was obtained at pH 5.2-5.4. No general acid or base catalysis from acetate, phosphate, or borate buffer species was observed. The catalytic rate constants on the protonated nefopam imposed by hydrogen ion and water was determined to be 7.16 X 10(-6) M-1 sec-1, and 4.54 X 10(-9) sec-1, respectively. The pKa of nefopam hydrochloride in aqueous solution was determined to be 8.98 +/- 0.33 (n = 3) at 25 +/- 0.2 degrees C by the spectrophotometric method. The catalytic rate constant of hydroxyl ion on the degradation of nefopam in either protonated or nonprotonated form was determined to be 6.63 X 10(-6) M-1 sec-1 and 4.06 X 10(-6) M-1 sec-1, respectively. A smaller effect of hydroxyl ion on the degradation of nonprotonated than on the degradation of protonated nefopam was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Stability of fluorouracil administered through four portable infusion pumps

The stability of fluorouracil in four portable infusion pumps under simulated infusion conditions was studied. Three commercially available fluorouracil aqueous solutions (50 mg/mL) were used. Samples adjusted to six pH levels were examined for precipitate. Drug reservoirs of four different portable infusion pumps were filled with 70 mL of each fluorouracil injection. Under conditions simulating actual use, the reservoirs were attached to the pumps and the solutions were pumped at a rate of 10 mL/24 hours over a seven-day period at 25 degrees C and 37 degrees C. Samples at the distal end of the extension tubing were collected hourly for the first 10 hours and at 12-hour intervals thereafter. Visual observations and pH determinations were made immediately. Drug concentrations were determined by reverse-phase high-performance liquid chromatography. Diethylhexylphthalate (DEHP) concentrations (the result of leaching from the plastic tubing and container) were determined by gas chromatography. In the pH study, precipitate appeared immediately in all fluorouracil injections below pH 8.52; precipitate was observed after two to four hours at pH 8.60-8.68. Under simulated infusion conditions, no apparent changes in concentration or pH were detected with any of the brands of drugs or portable infusion devices. At 25 degrees C, a fine white precipitate was observed in the extension tubing of all devices with the Roche brand of fluorouracil 48 to 96 hours after the pumping cycle began. The amount of DEHP leached from the drug reservoirs over the seven-day period was less than 1 ppm at both temperatures. All tested brands of fluorouracil injection were found to be stable under simulated infusion conditions over a seven-day period at 37 degrees C.

[The protective effect of endogenous and exogenous somatostatin on monolayer cultured islet B cells damaged by streptozotocin]

Exogenous administration of somatostatin exerted a beneficial influence directly on monolayer cultured islet B cells damaged by streptozotocin (3.0 mmol/L). Six to twelve hours following the pretreatment with somatostatin of 0.025, 0.05 and 0.1 microgram/ml the number of viable cells was significantly increased from 41.13 +/- 0.65 x 10(4) cells/ml (STZ control) to 49.0 +/- 2.0, 53.0 +/- 1.33, 53.38 +/- 1.74 x 10(4) cells/ml, respectively. The ultrastructural appearance of the B cells indicated that with many vacuoles and granules occurred in the cytoplasma of these cells, normal organelles disappeared and the nuclei were obscure in structure. The pretreatment with somatostatin (0.1 microgram/ml) protected the B cells against streptozotocin, with mitochondria, Golgi's apparatus and granules in these cells intact. The destruction of B cells induced by streptozotocin was more severe after adding anti-somatostatin serum to neutralize the endogenous somatostatin in the culture, which was reversed by replenishment of somatostatin. Adding Ca2+ carrier A23187 did not change the protective effect of somatostatin, it seemed that there was no relationship between the protective effect of somatostatin and calcium mechanism.

[The increase of protein synthesis by zinc can resist the damage induced by streptozotocin on islet cells]

The beneficial effect of ZnCl2 on islet cells injured by streptozotocin was observed directly on the cultured cells and its possible mechanism was analysed. The results were as follows: (1) The number of viable cells in culture was reduced from 70 x 10(5)/ml to 43.93 +/- 1.16 x 10(5)/ml 12 hours after adding normal saline plus STZ (3.0 mmol/L), and this reduction could be alleviated by adding ZnCl2 (0.25, 0.5, 1.0 mmol/L) in varying amounts and a dose-response relationship was found. The number of viable cells was returned to 47.39 +/- 0.88 x 10(5)/ml, 58.06 +/- 2.29 x 10(5)/ml, and 67.72 +/- 1.48 x 10(5)/ml respectively in the culture with ZnCl2 of different levels. (2) The effect of ZnCl2 was reversed when cycloheximide (100 micrograms/ml), a protein synthesis inhibitor, was added into the cultural medium, and the number of viable cells was again decreased from 63.17 +/- 2.15 x 10(5)/ml to 45.77 +/- 0.76 x 10(5) ml. No obvious effect was observed when cycloheximide was given alone. (3) The experiment of 3H-leucine incorporation into islet cells showed that protein synthesis was increased slightly and insignificantly after adding ZnCl2 (1.0 mmol/L). However, there was a significant increase of protein synthesis in cells when ZnCl2 (1.0 mmol/L) was added with STZ (3.0 mmol/L). The results suggest that ZnCl2 has a protective effect on the damaged islet cells induced by STZ. The increase of protein synthesis may be one of the mechanisms involved in the action of ZnCl2, which strengthens the repairing ability of islet cells after injury.

Stability of morphine sulfate in portable pump reservoirs during storage and simulated administration

The stability of four concentrations of morphine sulfate injection in prefilled reservoirs for portable infusion pumps was studied after storage for 30 days at refrigerated and room temperature and after a three-day simulated administration period at body temperature. Thirty-milliliter samples of morphine sulfate injections in four concentrations--1, 5, 15, and 25 mg/mL--were loaded into a pump reservoir. The reservoirs were stored in the dark at 5 degrees C and 25 degrees C for 30 days. Samples were taken from each reservoir immediately after loading and after 7, 14, and 30 days of storage. The reservoirs were then connected to portable infusion pumps, which were run for three days at a flow rate of 0.4 mL/hr at 37 degrees C. The last sample was collected at the end of the three-day period. Samples were assayed for morphine sulfate content by high-performance liquid chromatography. The concentration of morphine sulfate increased up to 6% (for the 5-mg/mL sample) at refrigerated temperature and up to 16% (for the 15-mg/mL sample) at room temperature after 30 days' storage in the reservoirs. Evaporation of water from the reservoirs may have accounted for this phenomenon. No absolute relationship was found between the initial concentration of morphine sulfate and the percentage concentration increase after storage for 30 days. The change in morphine sulfate concentration before and after the three-day pumping period was not significant. Injectable solutions of morphine sulfate in concentrations ranging from 1 to 25 mg/mL are stable when stored at refrigerated temperature for 30 days in a prefilled drug reservoir.

Pharmacokinetics of trimethoprim in the rat

The pharmacokinetics of trimethoprim was studied in male Sprague-Dawley rats following the intravenous administration of trimethoprim at a dose of 25 mg/kg. Plasma and tissue levels of trimethoprim, as a function of time, were determined by reversed-phase high-performance liquid chromatography. The disposition of trimethoprim was described by both a two-compartment open model with elimination from a central compartment and a noncompartmental method. For the compartmental analysis, the terminal elimination rate constant, elimination half-life, apparent volume of distribution in the central compartment, apparent volume of distribution in the central compartment based on the area under the plasma concentration-time curve, and volume of distribution at steady state, were determined to be 0.007 min-1, 99 min, 2059 mL/kg, 5729 mL/kg, and 2473 mL/kg, respectively. Noncompartmental pharmacokinetic parameters were obtained by the statistical moment theory. The estimates for mean residence time, clearance, and volume of distribution at steady state of trimethoprim were calculated to be 52 min, 40 mL.min-1kg-1, and 2097 mL, respectively. Tissue distribution of trimethoprim followed a biphasic phenomenon with a maximum concentration at 30 min for heart, lung, spleen, liver, kidney, seminal vesicles, and muscle, and at 45 min for testicles, 20 min for prostate gland, and less than 10 min for brain. The data show that compared with the plasma concentration, higher levels of trimethoprim were found in heart, lung, spleen, liver, kidney, prostate gland, and seminal vesicles; a similar concentration was found for muscle, but lower levels of trimethoprim were found for brain and testicles.

Stability of cefazolin sodium, cefoxitin sodium, ceftazidime, and penicillin G sodium in portable pump reservoirs

The stability of cefazolin sodium, cefoxitin sodium, ceftazidime, and penicillin G sodium in prefilled drug reservoirs that were stored at -20 degrees C for 30 days, thawed at 5 degrees C for four days, and pumped at 37 degrees C for one day was studied. Each antimicrobial agent was diluted with sterile water for injection to a concentration representative of the most common dosage when administered via a portable infusion pump. Ten milliliters of each drug solution was placed in individual glass vials to serve as controls, and volumes appropriate to deliver the designated dosages were loaded into the drug reservoirs. Triplicate reservoirs were prepared for each drug. One-milliliter samples from all containers were taken on days 0, 30, 31, 32, 33, 34, 34.5, and 35. All solutions were observed for color change and precipitation. Drug concentrations were determined using high-performance liquid chromatography. Leaching of the plasticizer diethylhexyl phthalate (DEHP) was analyzed by packed-column gas chromatography on days 0 and 35. No color change or precipitation was observed. No DEHP concentrations above 1 ppm were detected. More than 90% of the initial concentrations of each drug remained, except penicillin G sodium, which had a mean concentration of 83.9 +/- 0.5% at the end of the study. Cefazolin sodium, cefoxitin sodium, and ceftazidime in admixtures with sterile water for injection are stable under the conditions of this study. Penicillin G sodium should not be administered for more than 12 hours after such a cycle of freezing and thawing.

In vitro iontophoretic studies using a synthetic membrane

In vitro iontophoretic administration of drugs through a microporous polyolefin membrane with hydrophilic urethane polymerfilled pores was done for the ionized drugs dexamethasone sodium phosphate, hydrocortisone sodium phosphate, and prednisolone sodium succinate, and for a nonionizable drug cortisone acetate. Currents between 0.2 and 0.8 mA were demonstrated to be effective in increasing the transmembrane transport rate compared with passive diffusion for all the ionizable drugs studied. However, these currents failed to show any significant effect on the transmembrane transport rate of the nonionizable drug, cortisone acetate. There was a good linear relationship between the applied current (I, mA) and the transmembrane transport rate (J, micrograms/mL) in the receptor cell for all the ionized drugs (J = 1.97I + 0.70 for dexamethasone sodium phosphate; J = 2.05I + 1.49 for hydrocortisone sodium succinate; J = 2.25I + 1.93 for prednisolone sodium succinate). This in vitro iontophoretic study demonstrated that electric fields interact more efficiently with charged than with uncharged molecules.

Stability of a nonaqueous trimethoprim preparation

A nonaqueous formulation of trimethoprim for injection was prepared, and the stability of the undiluted solution (50 mg/mL) was studied. Six nonaqueous injectable solvents were used in an attempt to attain a trimethoprim concentration of 50 mg/mL; N,N-dimethylacetamide was found suitable, and a cosolvent system containing 52% N,N-dimethylacetamide and 48% propylene glycol was developed. The stability of trimethoprim 50 mg/mL in this solution after storage at temperatures of 80 degrees C, 90 degrees C, and 140 degrees C was studied using high-performance liquid chromatography. Samples were also examined visually for signs of color change or precipitation. More than 90% of the initial concentration remained after storage at 80 degrees C for 45 days. Examination of the stability data suggested that trimethoprim degradation was a zero-order process, although a first-order process could not be excluded. Extrapolation of data from an Arrhenius plot yielded a zero-order trimethoprim degradation rate constant at 25 degrees C of 0.0113% day-1. The time for 10% trimethoprim degradation at 25 degrees C would be 885 days. No precipitation was observed, but the initially colorless solution turned yellow or brown during storage. The extent of color change was associated with the degree of trimethoprim degradation. Trimethoprim, when prepared in the nonaqueous solution described, is stable at 25 degrees C. The preparation may be suitable for intravenous use.

Degradation kinetics of phentolamine hydrochloride in solution

The degradation kinetics of phentolamine hydrochloride in aqueous solution over a pH range of 1.2 to 7.2 and its stability in propylene glycol- or polyethylene glycol 400-based solutions were investigated. The observed rate constants were shown to follow apparent first-order kinetics in all cases. The pKa determination for phentolamine hydrochloride was found to be 9.55 +/- 0.10 (n = 5) at 25 +/- 0.2 degrees C. This indicated the protonated form of phentolamine occurs in the pH range of this study. The pH-rate profile indicated a pH-independent region (pH 3.1-4.9) exists with a minimum rate around pH 2.1. The catalytic effect of acetate and phosphate buffer species is ordinary. The catalytic rate constants imposed by acetic acid, acetate ion, dihydrogen phosphate ion, and monohydrogen phosphate ion were determined to be 0.018, 0.362, 0.036, and 1.470 L mol-1 h-1, respectively. The salt effect in acetate and phosphate buffers followed the modified Debye-Huckel equation quite well. The ZAZB value obtained from the experiment closely predicts the charges of the reacting species. The apparent energy of activation was determined to be 19.72 kcal/mol for degradation of phentolamine hydrochloride in pH 3.1, 0.1 M acetate buffer solution at constant ionic strength (mu = 0.5). Irradiation with 254 nm UV light at 25 +/- 0.2 degrees C showed a ninefold increase in the degradation rate compared with the light-protected control. Propylene glycol had little or no effect on the degradation of phentolamine hydrochloride at 90 +/- 0.2 degrees C; however, polyethylene glycol 400 had a definite effect.

Stability of amoxicillin trihydrate-potassium clavulanate in original containers and unit dose oral syringes

The stability of reconstituted amoxicillin trihydrate-potassium clavulanate oral suspension both in original containers and pre-packaged in commercially available oral syringes stored at various temperatures was determined. Amoxicillin trihydrate 125 mg/5 mL-potassium clavulanate 31.25 mg/5 mL and amoxicillin trihydrate 250 mg/5 mL-potassium clavulanate 62.5 mg/5 mL were reconstituted according to the manufacturer's instructions. The reconstituted suspensions in the original containers and in five brands of oral syringes were stored at 5 degrees C and 25 degrees C and -10 degrees C, 5 degrees C, and 25 degrees C, respectively, for 0, 2, 4, 7, and 14 days. The concentrations of amoxicillin trihydrate and potassium clavulanate remaining after storage were assayed in triplicate by reverse-phase high-performance liquid chromatography, using a stability-indicating method. An F statistic was calculated to determine whether different syringe brands had significantly different effects on drug stability. Amoxicillin trihydrate was stable for at least 10 days in the original containers and all types of oral syringes at 5 degrees C. However, potassium clavulanate was stable for 11.1 days in original containers and less than 5 days in all types of oral syringes at 5 degrees C. The effect of syringe brand on the stability of drugs over time at specific storage conditions and temperature was significant for potassium clavulanate at 5 degrees C and for both amoxicillin trihydrate and potassium clavulanate at 25 degrees C. The manufacturer's guidelines for storage of reconstituted amoxicillin trihydrate-potassium clavulanate oral suspension in the original containers should not be applied to dosages repackaged in unit dose oral syringes.

Stability of papaverine hydrochloride and phentolamine mesylate in injectable mixtures

The stability of papaverine hydrochloride and phentolamine mesylate combined in a single vial was studied. Injectable mixtures (10 mL) of papaverine hydrochloride 300 mg and phentolamine mesylate 5 mg (from two sources) were prepared by adding the contents of one vial of lyophilized phentolamine mesylate to the contents of one vial of papaverine hydrochloride injection. The vials were stored at 5 degrees C and 25 degrees C. Duplicate aliquots of the mixtures were obtained, and the concentrations of papaverine hydrochloride and phentolamine mesylate remaining at time 0 and after 1, 2, 5, 10, 20, and 30 days were determined in triplicate by a stability-indicating high-performance liquid chromatographic assay. The concentration of papaverine hydrochloride stored in the vials remained constant (less than 1% loss) over the 30-day period at both 5 degrees C and 25 degrees C. Phentolamine mesylate was less stable than papaverine but still retained more than 97% of its original concentration after 30 days at 5 degrees C and more than 95% of its original concentration at 25 degrees C. Papaverine hydrochloride and phentolamine mesylate are stable in injectable mixtures when stored for up to 30 days at 5 degrees C or 25 degrees C.