Modeling the Bioactivation and Subsequent Reactivity of Drugs

Electrophilically reactive drug metabolites are implicated in many adverse drug reactions. In this mechanism-termed bioactivation-metabolic enzymes convert drugs into reactive metabolites that often conjugate to nucleophilic sites within biological macromolecules like proteins. Toxic metabolite-product adducts induce severe immune responses that can cause sometimes fatal disorders, most commonly in the form of liver injury, blood dyscrasia, or the dermatologic conditions toxic epidermal necrolysis and Stevens-Johnson syndrome. This study models four of the most common metabolic transformations that result in bioactivation: quinone formation, epoxidation, thiophene sulfur-oxidation, and nitroaromatic reduction, by synthesizing models of metabolism and reactivity. First, the metabolism models predict the formation probabilities of all possible metabolites among the pathways studied. Second, the exact structures of these metabolites are enumerated. Third, using these structures, the reactivity model predicts the reactivity of each metabolite. Finally, a feedfoward neural network converts the metabolism and reactivity predictions to a bioactivation prediction for each possible metabolite. These bioactivation predictions represent the joint probability that a metabolite forms and that this metabolite subsequently conjugates to protein or glutathione. Among molecules bioactivated by these pathways, we predicted the correct pathway with an AUC accuracy of 89.98%. Furthermore, the model predicts whether molecules will be bioactivated, distinguishing bioactivated and nonbioactivated molecules with 81.06% AUC. We applied this algorithm to withdrawn drugs. The known bioactivation pathways of alclofenac and benzbromarone were identified by the algorithm, and high probability bioactivation pathways not yet confirmed were identified for safrazine, zimelidine, and astemizole. This bioactivation model-the first of its kind that jointly considers both metabolism and reactivity-enables drug candidates to be quickly evaluated for a toxicity risk that often evades detection during preclinical trials. The XenoSite bioactivation model is available at http://swami.wustl.edu/xenosite/p/bioactivation.

Meloxicam methyl group determines enzyme specificity for thiazole bioactivation compared to sudoxicam

Meloxicam is a thiazole-containing NSAID that was approved for marketing with favorable clinical outcomes despite being structurally similar to the hepatotoxic sudoxicam. Introduction of a single methyl group on the thiazole results in an overall lower toxic risk, yet the group's impact on P450 isozyme bioactivation is unclear. Through analytical methods, we used inhibitor phenotyping and recombinant P450s to identify contributing P450s, and then measured steady-state kinetics for bioactivation of sudoxicam and meloxicam by the recombinant P450s to determine relative efficiencies. Experiments showed that CYP2C8, 2C19, and 3A4 catalyze sudoxicam bioactivation, and CYP1A2 catalyzes meloxicam bioactivation, indicating that the methyl group not only impacts enzyme affinity for the drugs, but also alters which isozymes catalyze the metabolic pathways. Scaling of relative P450 efficiencies based on average liver concentration revealed that CYP2C8 dominates the sudoxicam bioactivation pathway and CYP2C9 dominates meloxicam detoxification. Dominant P450s were applied for an informatics assessment of electronic health records to identify potential correlations between meloxicam drug-drug interactions and drug-induced liver injury. Overall, our findings provide a cautionary tale on assumed impacts of even simple structural modifications on drug bioactivation while also revealing specific targets for clinical investigations of predictive factors that determine meloxicam-induced idiosyncratic liver injury.

Dual mechanisms suppress meloxicam bioactivation relative to sudoxicam

Thiazoles are biologically active aromatic heterocyclic rings occurring frequently in natural products and drugs. These molecules undergo typically harmless elimination; however, a hepatotoxic response can occur due to multistep bioactivation of the thiazole to generate a reactive thioamide. A basis for those differences in outcomes remains unknown. A textbook example is the high hepatotoxicity observed for sudoxicam in contrast to the relative safe use and marketability of meloxicam, which differs in structure from sudoxicam by the addition of a single methyl group. Both drugs undergo bioactivation, but meloxicam exhibits an additional detoxification pathway due to hydroxylation of the methyl group. We hypothesized that thiazole bioactivation efficiency is similar between sudoxicam and meloxicam due to the methyl group being a weak electron donator, and thus, the relevance of bioactivation depends on the competing detoxification pathway. For a rapid analysis, we modeled epoxidation of sudoxicam derivatives to investigate the impact of substituents on thiazole bioactivation. As expected, electron donating groups increased the likelihood for epoxidation with a minimal effect for the methyl group, but model predictions did not extrapolate well among all types of substituents. Through analytical methods, we measured steady-state kinetics for metabolic bioactivation of sudoxicam and meloxicam by human liver microsomes. Sudoxicam bioactivation was 6-fold more efficient than that for meloxicam, yet meloxicam showed a 6-fold higher efficiency of detoxification than bioactivation. Overall, sudoxicam bioactivation was 15-fold more likely than meloxicam considering all metabolic clearance pathways. Kinetic differences likely arise from different enzymes catalyzing respective metabolic pathways based on phenotyping studies. Rather than simply providing an alternative detoxification pathway, the meloxicam methyl group suppressed the bioactivation reaction. These findings indicate the impact of thiazole substituents on bioactivation is more complex than previously thought and likely contributes to the unpredictability of their toxic potential.

Comprehensive kinetic and modeling analyses revealed CYP2C9 and 3A4 determine terbinafine metabolic clearance and bioactivation

Terbinafine N-dealkylation pathways result in formation of 6,6-dimethyl-2-hepten-4-ynal (TBF-A), a reactive allylic aldehyde, that may initiate idiosyncratic drug-induced liver toxicity. Previously, we reported on the importance of CYP2C19 and 3A4 as major contributors to TBF-A formation. In this study, we expanded on those efforts to assess individual contributions of CYP1A2, 2B6, 2C8, 2C9, and 2D6 in terbinafine metabolism. The combined knowledge gained from these studies allowed us to scale the relative roles of the P450 isozymes in hepatic clearance of terbinafine including pathways leading to TBF-A, and hence, provide a foundation for assessing their significance in terbinafine-induced hepatotoxicity. We used in vitro terbinafine reactions with recombinant P450s to measure kinetics for multiple metabolic pathways and calculated contributions of all individual P450 isozymes to in vivo hepatic clearance for the average human adult. The findings confirmed that CYP3A4 was a major contributor (at least 30% total metabolism) to all three of the possible N-dealkylation pathways; however, CYP2C9, and not CYP2C19, played a critical role in terbinafine metabolism and even exceeded CYP3A4 contributions for terbinafine N-demethylation. A combination of their metabolic capacities accounted for at least 80% of the conversion of terbinafine to TBF-A, while CYP1A2, 2B6, 2C8, and 2D6 made minor contributions. Computational approaches provide a more rapid, less resource-intensive strategy for assessing metabolism, and thus, we additionally predicted terbinafine metabolism using deep neural network models for individual P450 isozymes. Cytochrome P450 isozyme models accurately predicted the likelihood for terbinafine N-demethylation, but overestimated the likelihood for a minor N-denaphthylation pathway. Moreover, the models were not able to differentiate the varying roles of the individual P450 isozymes for specific reactions with this particular drug. Taken together, the significance of CYP2C9 and 3A4 and to a lesser extent, CYP2C19, in terbinafine metabolism is consistent with reported drug interactions. This finding suggests that variations in individual P450 contributions due to other factors like polymorphisms may similarly contribute to terbinafine-related adverse health outcomes. Nevertheless, the impact of their metabolic capacities on formation of reactive TBF-A and consequent idiosyncratic hepatotoxicity will be mitigated by competing detoxification pathways, TBF-A decay, and TBF-A adduction to glutathione that remain understudied.

An anomalous band originating from the fabella causing semimembranosus impingement presenting as knee pain: a case report

Background

The presentation of patients with knee injuries which can have a significant impact on their ability to work and perform activities of daily living is constantly rising. The posterolateral corner of the knee has a complex anatomy of muscles, tendons, and ligaments, with huge variation in the population. The fabella is one such structure, found in the posterolateral corner of the knee, which can serve as a common origin point of various ligaments.

Case report

We present a case report of a 53-year-old white man who presented with atraumatic, posterior knee pain and was found to have a congenital, anomalous band originating from the fabella, causing semimembranosus impingement. This was diagnosed with magnetic resonance imaging; he underwent division of the anomalous band, which resulted in complete resolution of his symptoms.

Conclusion

We propose that patients who present with posterior knee pain, without any history of trauma, and have no abnormalities on plain radiographs, should undergo magnetic resonance imaging of their knees. This will help in assessing the ligament complex in the posterior compartment of the knee, and exclude impingement of the semimembranosus as an, albeit rare, cause of posteromedial knee pain.

Distributed and dynamic modelling of hydrology, phosphorus and ecology in the Hampshire Avon and Blashford Lakes: evaluating alternative strategies to meet WFD standards

The issues of diffuse and point source phosphorus (P) pollution in the Hampshire Avon and Blashford Lakes are explored using a catchment model of the river system. A multibranch, process based, dynamic water quality model (INCA-P) has been applied to the whole river system to simulate water fluxes, total phosphorus (TP) and soluble reactive phosphorus (SRP) concentrations and ecology. The model has been used to assess impacts of both agricultural runoff and point sources from waste water treatment plants (WWTPs) on water quality. The results show that agriculture contributes approximately 40% of the phosphorus load and point sources the other 60% of the load in this catchment. A set of scenarios have been investigated to assess the impacts of alternative phosphorus reduction strategies and it is shown that a combined strategy of agricultural phosphorus reduction through either fertiliser reductions or better phosphorus management together with improved treatment at WWTPs would reduce the SRP concentrations in the river to acceptable levels to meet the EU Water Framework Directive (WFD) requirements. A seasonal strategy for WWTP phosphorus reductions would achieve significant benefits at reduced cost.

A simple electronic alert for acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is frequently under-recognized and contributes to poor outcomes. Electronic alerts (e-alerts) to highlight AKI based on changes in serum creatinine may facilitate earlier recognition and treatment, and sophisticated algorithms for AKI detection have been proposed or implemented elsewhere. However, many laboratories currently lack the resources or capability to replicate these systems.

METHODS

A real-time automated delta check e-alert flags a 50% increase in creatinine to a concentration of >50 µmol/L from the most recent result within a 90-day period and automatically adds the comment '?AKI - creatinine increase >50% from previous' with a link to local AKI guidelines. In addition, creatinine results >300 µmol/L are retrospectively reviewed and phoned if AKI is suspected. For each alert over a 12-day period we manually reviewed previous and subsequent creatinine results to determine baseline creatinine and stage AKI according to Acute Kidney Injury Network (AKIN) criteria.

RESULTS

From 11,930 creatinine requests, 63 of 90 (70%) delta check e-alerts were due to AKI, identifying 61 episodes of AKI. Thirty four of 54 (63%) creatinine results >300 µmol/L were due to AKI, identifying a further 10 episodes of AKI. The positive predictive value (PPV) for AKI of a delta check e-alert was greater when the trigger creatinine was >100 µmol/L (PPV 89%) or when the absolute change in creatinine was >50 µmol/L (PPV 93%).

CONCLUSION

This study demonstrates that a simple automated delta check can detect and flag AKI in real time, continuously, at little extra cost and without manual input.

Enhanced 3-epi-25-hydroxyvitamin D3 signal leads to overestimation of its concentration and amplifies interference in 25-hydroxyvitamin D LC-MS/MS assays

Background

3-epi-25-hydroxyvitamin D3 (3-epi-25OHD3) interferes in most liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for 25-hydroxyvitamin D (25OHD). The clinical significance of this is unclear, with concentrations from undetectable to 230 nmol/L reported. Many studies have quantified 3-epi-25OHD3 based on 25OHD3 calibrators or other indirect methods, and we speculated that this contributes to the observed variability in reported 3-epi-25OHD3 concentrations.

Methods

We compared continuous MS/MS infusions of 3-epi-25OHD3 and 25OHD3 solutions, spiked both analytes into the same serum matrix and analysed patient samples to assess the effect of three different quantitation methods on 3-epi-25OHD3 concentration. Experiments were performed on an LC-MS/MS system using a phenyl column which does not resolve 3-epi-25OHD3, and a modified method utilizing a Zorbax SB-CN column that chromatographically resolves 3-epi-25OHD3 from 25OHD3.

Results

A greater 3-epi-25OHD3 signal, compared with 25OHD3, was observed during equimolar post-column continuous infusion of analyte solutions, and following analysis of a serum pool spiked with both analytes. 3-epi-25OHD3 signal enhancement was dependent on mobile phase composition. Compared with 3-epi-25OHD3 calibrators, indirect quantitation methods resulted in up to 10 times as many samples having 3-epi-25OHD3 concentrations ≥ 10 nmol/L, and an approximately fourfold increase in the maximum observed 3-epi-25OHD3 concentration to 95 nmol/L.

Conclusions

Enhanced 3-epi-25OHD3 signal leads to overestimation of its concentrations in the indirect quantitation methods used in many previous studies. The enhanced signal may contribute to greater interference in some 25OHD LC-MS/MS assays than others. We highlight that equimolar responses cannot be assumed in LC-MS/MS systems, even if two molecules are structurally similar.

On modelling the impacts of phosphorus stripping at sewage works on in-stream phosphorus and macrophyte/epiphyte dynamics: a case study for the River Kennet

A new model of in-stream phosphorus and macrophyte dynamics, 'The Kennet model', was applied to a reach of the River Kennet, southern England. The reach, which is 1.5 km long, is immediately downstream of Marlborough sewage treatment works, where phosphorus reduction by tertiary effluent treatment began in September 1997. The model is used to simulate the flow, water chemistry and macrophyte biomass within the reach, both before and after phosphorus removal from the effluent. Monte Carlo experiments coupled with a general sensitivity analysis indicate that the model offers a feasible explanation for the salient aspects of the system behaviour. Model simulations indicate that epiphyte smothering is an important limitation to macrophyte growth, and that higher stream and pore water soluble reactive phosphorus (SRP) concentrations allow the earlier onset of growth for the epiphytes and macrophytes, respectively. Higher flow conditions are shown to reduce the simulated peak epiphyte biomass; though at present, the effect of flow on the macrophyte biomass is unclear. Another simulation result suggests that phosphorus will not be released from the bed sediments in this reach following phosphorus removal from the effluent.

Hepatitis C in methadone maintenance patients: prevalence and public policy implications

OBJECTIVE

This study measured the extent and examined implications of hepatitis C (HCV) infection in a methadone maintenance treatment (MMT) population.

METHOD

Four hundred and sixty patients were tested for HCV-Ab, hepatic enzymes and bilirubin, HCV-RNA, and hepatitis B antibody.

RESULTS

Overall, 87% of this population had evidence of HCV-Ab. Among drug injectors (IDU), 96% were HCV-Ab positive. Among a subset of Laotian opium-smoking patients prevalence was only 11%. Sixty-two percent of patients with HCV-Ab had detectable HCV-RNA. Only 41% had elevated hepatic enzymes, and 5% had elevated bilirubin levels. All age groups were equally infected. Systemic problems in screening and treating HCV in drug users were identified.

CONCLUSION

HCV infection poses significant long-term health risks for this population. Harm reduction interventions aimed at reducing transmission of HCV and other needle-related infectious disease deserves more consideration.

A comparison of bone remodelling around hydroxyapatite-coated, porous-coated and grit-blasted hip replacements retrieved at post-mortem

We investigated the implant-bone interface around one design of femoral stem, proximally coated with either a plasma-sprayed porous coating (plain porous) or a hydroxyapatite porous coating (porous HA), or which had been grit-blasted (Interlok). Of 165 patients implanted with a Bimetric hip hemiarthroplasty (Biomet, Bridgend, UK) specimens were retrieved from 58 at post-mortem.

We estimated ingrowth and attachment of bone to the surface of the implant in 21 of these, eight plain porous, seven porous HA and six Interlok, using image analysis and light morphometric techniques. The amount of HA coating was also quantified.

There was significantly more ingrowth (p = 0.012) and attachment of bone (p > 0.05) to the porous HA surface (mean bone ingrowth 29.093 ± 2.019%; mean bone attachment 37.287 ± 2.489%) than to the plain porous surface (mean bone ingrowth 21.762 ± 2.068%; mean bone attachment 18.9411 ± 1.971%). There was no significant difference in attachment between the plain porous and Interlok surfaces. Bone grew more evenly over the surface of the HA coating whereas on the porous surface, bone ingrowth and attachment occurred more on the distal and medial parts of the coated surface. No significant differences in the volume of HA were found with the passage of time.

This study shows that HA coating increases the amount of ingrowth and attachment of bone and leads to a more even distribution of bone over the surface of the implant. This may have implications in reducing stress shielding and limiting osteolysis induced by wear particles.

A comparison of bone remodelling around hydroxyapatite-coated, porous-coated and grit-blasted hip replacements retrieved at post-mortem

We investigated the implant-bone interface around one design of femoral stem, proximally coated with either a plasma-sprayed porous coating (plain porous) or a hydroxyapatite porous coating (porous HA), or which had been grit-blasted (Interlok). Of 165 patients implanted with a Bimetric hip hemiarthroplasty (Biomet, Bridgend, UK) specimens were retrieved from 58 at post-mortem. We estimated ingrowth and attachment of bone to the surface of the implant in 21 of these, eight plain porous, seven porous HA and six Interlok, using image analysis and light morphometric techniques. The amount of HA coating was also quantified. There was significantly more ingrowth (p = 0.012) and attachment of bone (p < 0.05) to the porous HA surface (mean bone ingrowth 29.093 +/- 2.019%; mean bone attachment 37.287 +/- 2.489%) than to the plain porous surface (mean bone ingrowth 21.762 +/- 2.068%; mean bone attachment 18.9411 +/- 1.971%). There was no significant difference in attachment between the plain porous and Interlok surfaces. Bone grew more evenly over the surface of the HA coating whereas on the porous surface, bone ingrowth and attachment occurred more on the distal and medial parts of the coated surface. No significant differences in the volume of HA were found with the passage of time. This study shows that HA coating increases the amount of ingrowth and attachment of bone and leads to a more even distribution of bone over the surface of the implant. This may have implications in reducing stress shielding and limiting osteolysis induced by wear particles.

Effect of highly active antiretroviral therapy on the incidence of HIV-related cytomegalovirus retinitis and retinal detachment

Cytomegalovirus retinitis (CMVR) is the most common intraocular infection encountered in ophthalmic practices. To assess the impact of highly active antiretroviral therapy (HAART) on the incidence of CMVR and subsequent retinal detachments, a retrospective review of the HIV+ patients seen at a single university and community-based practice between 1992-1993 (group 1), before the advent of protease inhibitors, was compared with the data obtained from October 1996 to October 1997 (group 2) and October 1997-1998 (group 3), after the widespread use of HAART. The incidence of CMVR and retinal detachment rates for each group was calculated and compared. Twenty five (2.6%) of 974 HIV+ patients in group 1 developed CMVR. Of these, four patients developed retinal detachment (16%). Group 2 had a total of 1084 HIV+ patients, 18 (1.7%) of whom developed CMVR, which indicates a 35% decline of the incidence of CMV retinitis at our institution (p = 0.052, Odds ratio = 0.533, Confidence interval 0.28-1.01) and three patients (20%) developed retinal detachment. Only 1 patient (0.07%) of 1274 patients in group 3 developed CMVR, which represents a 99% reduction since 1993 (p = 0.0000000456). We conclude that the incidence of CMVR at this institution has decreased significantly with the recent use of HAART therapy. This effect may be related to the aggressive use of HAART and associated immune recovery in this population of AIDS patients. In this small series, however, the rate of retinal detachment appeared unchanged, but was only observed in those individuals who were not on HAART or who had just recently started.

Methamphetamine use and sexual and injection risk behaviors among out-of-treatment injection drug users

Our primary objective was to examine the relationship between methamphetamine use and sexual risk-taking behaviors--number of sexual partners, frequency of sexual behaviors with regular and casual partners, trading money or drugs for sex, and condom use--among male and female out-of-treatment injection drug users (OTIDUs). As a risk group for human immunodeficiency virus (HIV) transmission, we also investigated injection behaviors by methamphetamine use. Data were collected from 1392 OTIDUs within the California counties of Fresno, Sacramento, and San Diego. Excluded from this cross-sectional survey were male OTIDUs engaging in sex with only or mostly men since 1978. In bivariate analyses, we found that male OTIDUs with a history of methamphetamine use had more sex partners and participated in more acts of anal insertive intercourse with casual partners and vaginal intercourse with regular and casual partners than male OTIDUs never using methamphetamines. In addition, a greater percentage of male OTIDUs using methamphetamines reported trading sex for money or drugs. Methamphetamine-using female OTIDUs participated in more acts of vaginal intercourse with regular male sex partners than female OTIDUs never using methamphetamines. By multivariate logistic regression, we found methamphetamine use related to consistent condom use among male OTIDUs and among male sex partners of female OTIDUs. Discriminant function analyses revealed that sexual risk taking could be differentiated by methamphetamine use among male OTIDUs. Methamphetamine use also correlated with using shared needles or syringes among male and female OTIDUs and was related to not always disinfecting used needles or syringes with bleach. Our findings suggest that methamphetamines may contribute to heterosexual HIV transmission.

A prospective randomized trial of intraoperative bupivacaine irrigation for management of shoulder-tip pain following laparoscopy

BACKGROUND

Postoperative shoulder-tip pain (STP) frequently occurs following laparoscopic surgery. In an attempt to abrogate this complication we prospectively evaluated the efficacy of intraoperative irrigation of the diaphragm with bupivacaine.

METHODS

One hundred and five consecutive patients undergoing laparoscopic surgery were prospectively randomized to treatment or control groups. Treatment group (B, n = 55) received irrigation with 10 mL 0.5% bupivacaine in 500 mL saline and control group (A, n = 50) received an equal volume of normal saline. Each dome of the diaphragm was irrigated with 250 mL of either solution at the end of surgery. Laparoscopic procedures performed included cholecystectomy (n = 63), Nissen fundoplication (n = 21), appendicectomy (n = 7), hernia repair (n = 4), and diagnostic laparoscopy (n = 10). Patients' anesthesia and perioperative analgesia were standardized. STP was recorded on a visual analogue pain scale (VAPS) in the recovery room immediately following surgery and at 4, 10, and 24 hours thereafter.

RESULTS

The overall incidence of STP in patients undergoing laparoscopic procedures was approximately 24%. Twenty-one patients (42%) in the control group and 4 patients (7%) in the treatment group complained of shoulder pain during the recording period (P = 0.003). Mean STP scores as recorded on VAPS were significantly lower in the bupivacaine group than in the control group from 4 to 24 hours after surgery (P < 0.01). Postoperative analgesia requirements were also significantly reduced in those patients receiving bupivacaine irrigation (P < 0.04).

CONCLUSION

Intraperitoneal irrigation with bupivacaine to both hemidiaphragms at the end of surgery significantly reduces both frequency and intensity of STP following laparoscopic procedures thus reducing patient morbidity.

Analgesia following appendicectomy--the value of peritoneal bupivacaine

PURPOSE

Peritoneal inflammation is an important feature in many patients presenting with appendicitis. The contribution of peritoneal nerve fibres to pain experienced after appendicectomy has received little attention.

METHOD

In this prospective double blind randomized study a consecutive series of 60 patients undergoing appendicectomy for suspected appendicitis were enrolled. A dose of 1.5 mg.kg-1 bupivacaine 0.5% was used. Group one patients received the entire dose of bupivacaine subcutaneously. Group two patients received half the dose subcutaneously (s.c.) and half the dose to the peritoneum. Pain scores were assessed pre-operatively and at 30 min, 12 and 24 hr post-operatively using a visual analogue scale. Time to first analgesia and total analgesia requirements in the first 24 hr were recorded.

RESULTS

The patients receiving the s.c. combined with peritoneal bupivacaine had a lower pain score 30 min post-operatively (32 +/- 2 vs 54 +/- 4; P < 0.0001), a longer time to first analgesia (248 +/- 20 vs 164 +/- 17 min; P = 0.002) as well as lower opioid (68 +/- 5 vs 100 +/- 7 mg; P = 0.0002) and non steroidal analgesic requirements (65 +/- 6 vs 96 +/- 6 mg; P = 0.007) in the first 24 hr post-operatively.

CONCLUSION

A combination of s.c. and peritoneal infiltration with bupivacaine is superior to skin infiltration alone in the relief of pain post appendicectomy.

The attitudes of patients and health care personnel to rectal drug administration following day case surgery

The use of suppositories has been examined following a recent case in which an anaesthetist was reported to the United Kingdom General Medical Council. This study examined the preference for routes of administration of post-operative analgesia. A semistructured interview with a written questionnaire was administered to 610 subjects (49 doctors; 62 nurses; 67 paramedical staff; 44 other hospital employees; 388 patients). Four hundred and fifty (74%) preferred the intravenous (i.v.) route, 24 (4%) preferred a suppository while 136 (22%) found either route acceptable. The i.v. route was most popular with young (98% under 20 years) females (79%) social class I subjects (90%), doctors (96%), nurses (95%), those who had never had a suppository (81%) and those who had ill effects following a previous suppository (95%). This result suggests that patients are more tolerant of suppositories than hospital staff but the majority prefer the i.v. route.

In vitro activity of readily available household materials against HIV-1: is bleach enough?

This report describes experiments assessing the effectiveness against HIV of potential disinfecting agents that are commonly available to IDU when they are sharing syringes. We exposed cell-free HIV, HIV-infected cells, and HIV-infected blood containing known quantities of HIV to household cleaning agents, alcohols, peroxide, and highly acidic materials for 1 min, in order to examine the effects of these materials on the infectivity of the HIV. Undiluted liquid laundry bleach and dilute liquid dish detergent reduced the number of culturable HIV to an undetectable level under the experimental conditions used. Diluted bleach was not completely effective. Other potential disinfecting agents, including ethanol, isopropyl alcohol, and hydrogen peroxide, were unable to disinfect high numbers of HIV-infected cells or infected blood. Liquid dish detergent warrants further study as a possible acceptable alternative to bleach. Our data provide support for recommendations to IDU that they disinfect shared syringes every time between users with full-strength liquid laundry bleach to reduce their risk of acquiring or transmitting HIV. When bleach is not available, liquid dish detergent or other available disinfecting agents such as rubbing alcohol, hydrogen peroxide, or high alcohol content beverages are more effective than water at disinfecting HIV, recognizing that these materials are less effective than bleach. Although these materials are effective, they should not be viewed as a substitute for decreased sharing of injection equipment by IDU, or increased availability of sterile needles and syringes.

Role of Guanylate Cyclase–cGMP Systems in Halothane-induced Vasodilation in Canine Cerebral Arteries

The cellular mechanisms through which halothane dilates blood vessels remain largely unknown. The present studies were designed to determine the effects of 0.59 and 0.9 mM halothane (equivalent to 2.0% and 3.0%, respectively) on tissue cyclic guanosine 3,5-monophosphate (cGMP) level and guanylate cyclase enzyme activity in canine middle cerebral arteries. Rings of cerebral arteries preconstricted with 5-hydroxytryptamine (0.2 microM) were exposed for 15 min to low or high concentrations of halothane or for 5 min to sodium nitroprusside (50 microM). The vessels were instantaneously frozen by immersing them in liquid N2; they then were homogenized, and the tissue cGMP levels were determined using radioimmunoassay. Halothane produced 2.23 +/- 0.44- and 4.47 +/- 0.87-fold increases in tissue cGMP levels over control at 0.59 and 0.9 mM, respectively. Sodium nitroprusside, a nitrovasodilator, also increased the tissue cGMP level 7.80 +/- 1.36-fold over the control value. To understand better the mechanisms of halothane-induced increase of tissue cGMP level, the effects of this anesthetic agent on guanylate cyclase enzyme activity were examined. Halothane, unlike sodium nitroprusside, did not modulate the activity of the soluble guanylate cyclase enzyme. However, halothane (1.0 mM), like atrial natriuretic factor (5 microM), stimulated the particulate guanylate cyclase enzyme activity. LY-83583 (6-anilino-5,8-quinolinedione, 10 microM), an agent that inhibits soluble guanylate cyclase activity, significantly reduced the response of the vessels to calcium ionophore (A23187, 0.4 microM), an endothelium-dependent vasodilator, without producing a significant effect on halothane-induced vasodilation. These results suggest that halothane-induced vasodilation of cerebral blood vessels is partly mediated by an increase in tissue cGMP levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Seroepidemiology of viral infections among intravenous drug users in northern California

Intravenous drug users are frequently exposed to parenterally transmitted viral infections, and these infections can spread to the general population through sexual activity. We investigated the prevalence of serologic markers for human immunodeficiency virus type 1 (HIV-1), human T-cell lymphotropic virus type I/II (HTLV-I/II), hepatitis B virus (HBV), and hepatitis C virus (HCV) in intravenous drug users and their sexual contacts. Of 585 drug users from northern California tested for these serologic markers, 72% were reactive for the antibody to HCV, 71% for the antibody to hepatitis B core antigen, 12% for HTLV-I/II antibodies, and 1% for the HIV-1 antibody. The prevalence of serologic markers for these four viruses correlated with the duration of intravenous drug use, the ethnic group, and the drug of choice. More than 85% of subjects infected with either HCV or HBV were coinfected with the other virus. All persons reactive to HTLV-I/II antibodies had antibodies for either HBV or HCV. Of 81 sexual contacts tested, 17% had evidence of HBV infection while only 6% were reactive for HTLV-I/II antibodies and 4% for the antibody to HCV. None of this group was infected with HIV-1. We conclude that HTLV-I/II and HCV are inefficiently transmitted to sexual contacts while HBV is spread more readily. Programs designed to discourage the sharing of drug paraphernalia, such as needle and syringe exchanges, should decrease the risk of parenterally spread viral infections in intravenous drug users and thus slow the spread of these infections to the general population.

Prevalence of hepatitis C virus antibodies among patients infected with human immunodeficiency virus

A study was undertaken to determine the prevalence and risk factors for serological evidence of hepatitis C virus (HCV) infection in patients infected with the human immunodeficiency virus (HIV). Tests for anti-HCV antibody were carried out by enzyme-linked immunoassay (EIA) on 101 HIV-infected patients from two university-based outpatient clinics. Anti-HCV antibody reactive samples were tested by using a recombinant immunoblot assay (RIBA) for HCV antibodies. Fourteen of 101 (13.9%) HIV-infected patients were anti-HCV reactive by EIA. Of these 14, only seven were reactive by RIBA: four were intravenous drug users as a sole risk factor for HIV infection; and the remaining three acquired HIV by blood transfusion, contaminated instrument exposure or IV drug use and sexual contact. Acquisition of HIV by sexual activity alone was not associated with HCV infection. It is concluded that HCV infection is found in approximately 7% of a university HIV clinic population. False-positive anti-HCV antibody serology may lead to overestimation of the prevalence of HCV infection. Female sex and intravenous drug use are significantly associated with HCV infection among HIV-infected individuals.

Zinc status in human immunodeficiency virus infection

Plasma zinc and copper concentrations, erythrocyte zinc concentration, copper-zinc superoxide dismutase activity and urinary zinc concentrations were determined for control subjects and individuals with AIDS, ARC, or asymptomatic HIV infection. Significant differences among the population groups were not noted for the above parameters with the exception of plasma copper which was higher in the AIDS group than in other patient groups. These results do not support the idea that zinc deficiency is a common contributory factor of HIV infectivity or clinical expression, nor that HIV infection induces a zinc deficiency.

The effect of local anaesthetics on epinephrine absorption following rectal mucosal infiltration

This study was undertaken to investigate the effects of lidocaine and bupivacaine on epinephrine absorption following rectal mucosal infiltration, to assess the cardiovascular and metabolic effects of the absorbed epinephrine and to compare the systemic absorption of the local anaesthetics employed. Three groups of five greyhounds received 1.5 micrograms.kg-1 of epinephrine 1:200,000 in lidocaine 0.5 per cent, bupivacaine 0.5 per cent or 0.9 per cent saline. Plasma epinephrine, lidocaine, bupivacaine, lactate, glucose and potassium concentrations were measured at 1, 2, 5, 10, 15 and 30 minutes following infiltration. Plasma epinephrine concentrations were significantly higher in the lidocaine group at one and two minutes following infiltration. Plasma bupivacaine concentrations were significantly higher than plasma lidocaine concentrations throughout the study period. There were no significant differences in metabolic or biochemical indices within or between the three groups. A local vasodilatory action of lidocaine may enhance epinephrine absorption. Differences in hepatic uptake and rate of metabolism may explain the increased plasma bupivacaine measured. Lidocaine may be the local anaesthetic of choice for ano-rectal procedures, especially when large volumes of local anaesthetic are being infiltrated.

Infusion carboplatin treatment of relapsed and refractory acute leukemia: evidence of efficacy with minimal extramedullary toxicity at intermediate doses

Carboplatin (CBDCA) is a second-generation platinum analog with prominent myelotoxicity and modest extramedullary toxicity. We performed a phase I study of CBDCA in adult patients with relapsed acute leukemia. Therapy was administered as a five-day continuous infusion. The initial dose of 875 mg/m2 over five days was escalated in 15% increments to a final dose of 2,100 mg/m2 over five days. Twenty-eight patients received 35 induction courses of CBDCA, including two patients who achieved a complete remission (CR) following the first course, and received a second induction course at the time of relapse. Therapy was well tolerated. No grade 3 or 4 extramedullary toxicity was seen. Myelosuppression was regularly observed, with prolonged myelosuppression at 2,100 mg/m2 over five days being the indication to cease dose escalation. Eight of 28 patients (28.5%) responded to CBDCA therapy (six CR, two partial remission [PR]) or ten of 30 initial induction courses (33.3%). Continuous-infusion CBDCA has an advantage over other therapy for acute leukemia because of its highly selective myelotoxicity and minimal gastrointestinal and renal toxicity. A standard phase II study should be undertaken to establish a more accurate response rate.

Ethylene production by soil microorganisms

Ethylene-producing strains of Penicillium cyclopium and P. crustosum were isolated from soil. These isolates produced ethylene on a variety of carbon growth substrates including phenolic acids. The quantities of ethylene produced on the various substrates varied, and the subtrate-ethylene prosuction pattern for P. cyclopium strains differed significantly from that of P. crustosum strains.