The readability and reliability of online information about adenoidectomy.

OBJECTIVE: There is limited understanding amongst patients and parents of paediatric patients regarding adenoidectomy. Most patients access health-related information online. The aim of this study was to assess the suitability of online information on adenoidectomy. METHOD: The term 'adenoid' was used to search Google, and the first 50 websites identified were screened. For each website, the readability and quality were assessed. RESULTS: Of the 41 websites that met the inclusion criteria, the mean readability scores corresponded to 'difficult to read' and university-level reading categories. For the quality of the websites, the mean score corresponded to 'fair' with 39 per cent of the websites containing either 'poor' or 'very poor' quality data. The ENT UK information is one of the most readable and reliable online resources. CONCLUSION: The online information on adenoidectomy is largely set at an inappropriate readability level and of variable quality. Surgeons should consider assisting their patients with online searches regarding adenoidectomy.

A policy of day-case sinonasal surgery is safe, well tolerated and cost-effective.

OBJECTIVE: Practices vary regarding the timing of discharge after sinonasal surgery. This study aimed to examine the cost-effectiveness of same-day discharge compared to next-day discharge after sinonasal surgery. METHODS: A retrospective single-surgeon audit of sinonasal surgery over a 12-month period was performed. Demographic and clinical details, including distance travelled home, timing of discharge, hospital re-presentation, and complications, were collected and compared between the same-day discharge and next-day discharge groups. A cost-effectiveness analysis was performed. RESULTS: A total of 181 patients were identified; 117 underwent day-case surgery, of which 6 re-presented to the emergency department. Sixty-four patients stayed overnight after surgery, and six of those patients re-presented to the emergency department. The per patient cost was $3262 for day-case sinonasal surgery and $5050 for those admitted overnight after surgery (p < 0.001). CONCLUSION: Routine same-day discharge after sinonasal surgery is achievable, safe and cost-effective.

Effectiveness of extensive sinus surgery with post-operative medical management for chronic rhinosinusitis.

OBJECTIVE: To prospectively assess treatment outcomes of chronic rhinosinusitis patients undergoing functional endoscopic sinus surgery and post-operative medical treatment over a prolonged follow-up period. METHODS: Patients undergoing functional endoscopic sinus surgery in the tertiary referral practice of a single surgeon were studied prospectively. Symptoms were scored by patients pre-operatively and over a minimum follow-up period of 12 months. RESULTS: The study comprised 200 non-consecutive patients. The median pre-operative symptom score was 16 (out of a maximum of 25) (95 per cent confidence interval = 15 to 17). Symptom scores reduced to a median of 7 (95 per cent confidence interval = 6 to 8) after 12 months of follow up (p < 0.0001). The median symptom score improved for all symptoms and across all patient subgroups. CONCLUSION: Extensive functional endoscopic sinus surgery offers significant and durable symptom improvement in patients with chronic rhinosinusitis refractory to medical treatment. This improvement extends to all patient subgroups. Prolonged medical therapy is recommended after functional endoscopic sinus surgery.

Materials characterization and histological analysis of explanted polypropylene, PTFE, and PET hernia meshes from an individual patient.

During its tenure in vivo, synthetic mesh materials are exposed to foreign body responses, which can alter physicochemical properties of the material. Three different synthetic meshes comprised of polypropylene, expanded polytetrafluoroethylene (ePTFE), and polyethylene terephthalate (PET) materials were explanted from a single patient providing an opportunity to compare physicochemical changes between three different mesh materials in the same host. Results from infrared spectroscopy demonstrated significant oxidation in polypropylene mesh while ePTFE and PET showed slight chemical changes that may be caused by adherent scar tissue. Differential scanning calorimetry results showed a significant decrease in the heat of enthalpy and melt temperature in the polypropylene mesh while the ePTFE and PET showed little change. The presence of giant cells and plasma cells surrounding the ePTFE and PET were indicative of an active foreign body response. Scanning electron micrographs and photo micrographs displayed tissue entrapment and distortion of all three mesh materials.

Is the Rehydrin TrDr3 from Tortula ruralis associated with tolerance to cold, salinity, and reduced pH? Physiological evaluation of the TrDr3-orthologue, HdeD from Escherichia coli in response to abiotic stress.

We have employed EST analysis in the resurrection moss Tortula ruralis to discover genes that control vegetative desiccation tolerance and describe the characterization of the EST-derived cDNA TrDr3 ( Tortula ruralis desiccation-stress related). The deduced polypeptide TRDR3 has a predicted molecular mass of 25.5 kDa, predicted pI of 6.7, and six transmembrane helical domains. Preliminary expression analyses demonstrate that the TrDr3 transcript ratio increases in response to slow desiccation relative to the hydrated control in both total and polysomal mRNA (mRNP fraction), which classifies TrDr3 as a rehydrin. Bioinformatic searches of the electronic databases reveal that Tortula TRDR3 shares significant similarities to the hdeD gene product ( HNS- dependent expression) from Escherichia coli. The function of the HdeD protein in E. coli is unknown, but it is postulated to be involved in a mechanism of acid stress defence. To establish the role of E. coli HdeD in abiotic stress tolerance, we determined the log survival percentage from shaking cultures of wild-type bacteria and the isogenic hdeD deletion strain (Delta hdeD) in the presence of low temperature (28 degrees C), elevated NaCl (5 % (w/v)), or decreased pH (4.5), or all treatments simultaneously. The Delta hdeD deletion strain was less sensitive, as compared to wild-type E. coli, in response to decreased pH ( p > 0.009), and the combination of all three stresses ( p > 0.0001).

Ten year experience with Aspire (Tissuemed) porcine bioprosthesis: single centre experience.

BACKGROUND: Aspire (Tissuemed) bioprosthesis is a third generation porcine bioprosthesis. 10-year outcome of this bioprosthesis is unknown. METHODS: We report our experience of 139 consecutive prosthesis implanted between 1990-1998. The clinical outcome was reviewed retrospectively. RESULTS: 126 patients (67 males and 59 females), mean age 68.4+/-8.4 years underwent 139 valve replacements. Sites of valve implantation included the aortic in 77 patients (61%); mitral in 35 patients (27%); aortic+mitral in 13 patients (10%) and tricuspid in 1 patient (0.8%). 32/126 patients (25%) also underwent concomitant coronary artery bypass grafting (CABG). 30-day mortality for the whole group was 8.7% (11/126) with no valve related deaths. Follow up was 98.4% complete with a mean follow up of 6.1+/-3.3 years (766 patient-years, range 0-10.2 years). Overall 10-year actuarial survival was 41+/-7% (AVR 49+/-10%, MVR 29+/-11%) and this was influenced by pre-operative poor left ventricular function (EF<30%) (p=0.007) and pre-operative NYHA class III/IV (p=0.001). Overall estimated 10-year actuarial freedom from valve related events (Kaplan-Meier) and valve related events expressed as linearised rates (%/patient-year) were: freedom from structural valve failure 97+/-2% (0.26%/patient-year); non-structural dysfunction 98+/-1% (0.13%/patient-year); freedom from prosthetic valve endocarditis 94+/-3% (0.39%/patient-year); freedom from significant haemorrhagic event 82+/-6% (1.33%/patient-year); freedom from thrombo-embolism 90+/-3% (0.91%/patient-year) and freedom from re-operation was 93+/-3% (0.52%/patient-year). CONCLUSION: In our experience Aspire (Tissuemed) porcine bioprosthesis functions satisfactorily at 10-years with low valve related complications. Further follow-up will determine its long-term durability.

Growth, carcass characteristics, muscle conjugated linoleic acid (CLA) content, and response to intravenous glucose challenge in high percentage Wagyu, Wagyu x Limousin, and Limousin steers fed sunflower oil-containing diet.

The effect of breed and diet on insulin response to glucose challenge and its relation to intramuscular fat deposition was determined in 36 steers with 12 each of greater than 87% Wagyu (referred to as Wagyu), Wagyu x Limousin, and Limousin breeds. Weaned steers were blocked by weight into heavy, medium, and light calves and placed in six pens with two pens per weight type and with two steers of each breed per pen. Three pens with steers from each weightclass were fed backgrounding and finishing diets for 259 d, while the other three pens were fed the same diets where 6% of the barley grain was replaced with sunflower oil. Prior to initiation of the finishing phase of the study the intravenous glucose tolerance test (VGTIT) was conducted in all steers. Once steers were judged as carrying adequate 12th-rib fat, based on weight and days on feed, they were harvested and graded and samples of the longissimus muscle were procured for determination of fat content and fatty acid composition. Dietary oil improved (P = 0.011; 0.06) ADG and feed conversion efficiency of steers during the latter part of backgrounding and only ADG during early part ofthe finishing period. Generally percent kidney, pelvic, and heart fat was the only adiposity assessment increased (P = 0.003) by dietary oil. The IVGTT results indicated that insulin response to intravenous glucose was lower in Limousin steers than in Wagyu steers. Dietary oil decreased (P = 0.052) fasting plasma insulin concentration in Wagyu steers compared with Limousin steers. The correlation coefficients among the IVGTT measures and intramuscular fat content or marbling score were less than 0.4, and only a negative trend existed between fasting insulin and USDA marbling scores. However, the carcasses of the Wagyu steers graded US Choice, and 66% of the Wagyu carcasses graded US Prime, which were substantially better than the quality grades obtained for the carcasses from the other breed types. Dietary oil did not affect muscle fat content but increased (P = 0.01) conjugated linoleic acid (CLA) concentrations by 339%. Results indicated that IVGTT measures were not appropriate indices of marbling potential in cattle and that dietary oil can enhance CLA content of beef.

A cDNA encoding ribosomal protein RPL15 from the desiccation-tolerant bryophyte Tortula ruralis: mRNA transcripts are stably maintained in desiccated and rehydrated gametophytes.

A Tortula ruralis cDNA, Rpl15, encoding a predicted polypeptide with significant similarity to the large-subunit ribosomal protein L15 (RPL15) was isolated from a desiccated gametophyte cDNA library, and is the first L15 homologue identified from a bryophyte. The deduced 203 amino acid polypeptide is approximately 24.1 kDa, with a predicted pI of 11.1, and shares extensive identity with rat RPL15 deduced polypeptide (>57%). RNA blot hybridization using total RNA demonstrated that Rpl15 is constitutively expressed in moss gametophytes during a desiccation-rehydration cycle and that Rpl15 mRNA transcripts are maintained in desiccated gametophytes as conserved mRNAs.

The translational apparatus of Tortula ruralis: polysomal retention of transcripts encoding the ribosomal proteins RPS14, RPS16 and RPL23 in desiccated and rehydrated gametophytes.

Tortula ruralis (Syntrichia ruralis) is an important model system for the study of plant vegetative desiccation tolerance. One of the most intriguing aspects of desiccation-tolerant plants is the maintenance of key cellular components in stable and viable forms in the desiccated state, particularly those related to the translational apparatus (i.e. ribosomes and ribosomal RNAs). This study investigated the third integral component of the translational apparatus, the ribosomal proteins. Three T. ruralis cDNAs encoding predicted polypeptides with significant similarity to ribosomal proteins were isolated from a cDNA expression library derived from the polysomal, messenger ribonucleoprotein particle (mRNP) fraction of desiccated gametophytes; Rps14 and Rps16 encode the small-subunit ribosomal proteins RPS14 and RPS16, respectively, and Rpl23 encodes the large-subunit ribosomal protein RPL23. RPS14, RPS16 and RPL23, the deduced polypeptides, have predicted molecular masses of 14.4 kDa, 16.2 kDa and 14.9 kDa and predicted pI's of 11.08, 10.34 and 10. 67, respectively. Phylogenetic analysis of the deduced amino acid sequences demonstrated that each of the T. ruralis proteins is most similar to ribosomal proteins from higher plants even though RPS14 and RPL23 show high divergence from their other plant counterparts. RNA blot hybridizations of RNAs present within the polysomal mRNP fraction (i.e. the 100 Kxg pellet) demonstrated that Rps14, Rps16 and Rpl23 are expressed in moss gametophytes during a desiccation-rehydration cycle and, according to the prior cDNA classification scheme in T. ruralis, are constitutive clones. These findings clearly demonstrated that Rps14, Rps16 and Rpl23 transcripts are retained within the polysomal fractions of desiccated gametophytes.

Increased drug delivery to the brain by P-glycoprotein inhibition.

BACKGROUND: Although the antidiarrheal loperamide is a potent opiate, it does not produce opioid central nervous system effects at usual doses in patients. On the basis of in vitro studies demonstrating that loperamide is a substrate for the adenosine triphosphate-dependent efflux membrane transporter P-glycoprotein, we postulated that inhibition of P-glycoprotein with quinidine would increase entry of loperamide into the central nervous system with resultant respiratory depression. METHODS: To test this hypothesis, a 16-mg dose of loperamide was administered to eight healthy male volunteers in the presence of either 600 mg quinidine, a known inhibitor of P-glycoprotein, or placebo. Central nervous system effects were measured by evaluation of the respiratory response to carbon dioxide rebreathing as a measure of opiate-induced respiratory depression. RESULTS: Loperamide produced no respiratory depression when administered alone, but respiratory depression occurred when loperamide (16 mg) was given with quinidine at a dose of 600 mg (P < .001). These changes were not explained by increased plasma loperamide concentrations. CONCLUSION: This study therefore demonstrates first the potential for important drug interactions to occur by a new mechanism, namely, inhibition of P-glycoprotein, and second that the lack of respiratory depression produced by loperamide, which allows it to be safely used therapeutically, can be reversed by a drug causing P-glycoprotein inhibition, resulting in serious toxic and abuse potential.

Mibefradil is a P-glycoprotein substrate and a potent inhibitor of both P-glycoprotein and CYP3A in vitro.

Mibefradil, a calcium T- and L-channel blocker developed for use in hypertension, was recently removed from the market after reports of severe drug-drug interactions. Mibefradil is known to inhibit various cytochrome P450 enzymes involved in drug metabolism, particularly CYP3A. However, the extent and the severity of the observed drug interactions in humans suggest that inhibition of additional systems important to drug disposition, such as the drug transporter P-glycoprotein (P-gp), may also have contributed to the severity of the mibefradil interactions. A polarized epithelial cell line, LLC-PK1, which does not express P-gp, and the derived L-MDR1 cell line, which overexpresses human P-gp, were used to study the effects of mibefradil on drug transport. A markedly greater basal-to-apical versus apical-to-basal transport of [H3]mibefradil was seen in the L-MDR1, but not in the LLC-PK1 cells, suggesting that the drug is a substrate of P-gp. Using a human intestinal cancer-derived cell line Caco-2, which constitutively expresses P-gp, mibefradil was shown to be a potent inhibitor of P-gp-mediated digoxin transport, with an IC50 of 1.6 microM. Additionally, the effect of mibefradil on CYP3A was assessed using human liver microsomes. Mibefradil inhibited CYP3A-mediated nifedipine oxidase activity with an IC50 of 0.8 microM, and a Ki of 0.6 microM. Thus, mibefradil is not only a P-gp substrate, but also a potent inhibitor of both P-gp and CYP3A. These data suggest that the severity of drug interactions seen with mibefradil use is due to the dual inhibition of both P-gp and CYP3A.

Loss-of-function mutations in the cathepsin C gene result in periodontal disease and palmoplantar keratosis.

Papillon-Lefèvre syndrome, or keratosis palmoplantaris with periodontopathia (PLS, MIM 245000), is an autosomal recessive disorder that is mainly ascertained by dentists because of the severe periodontitis that afflicts patients. Both the deciduous and permanent dentitions are affected, resulting in premature tooth loss. Palmoplantar keratosis, varying from mild psoriasiform scaly skin to overt hyperkeratosis, typically develops within the first three years of life. Keratosis also affects other sites such as elbows and knees. Most PLS patients display both periodontitis and hyperkeratosis. Some patients have only palmoplantar keratosis or periodontitis, and in rare individuals the periodontitis is mild and of late onset. The PLS locus has been mapped to chromosome 11q14-q21 (refs 7, 8, 9). Using homozygosity mapping in eight small consanguineous families, we have narrowed the candidate region to a 1.2-cM interval between D11S4082 and D11S931. The gene (CTSC) encoding the lysosomal protease cathepsin C (or dipeptidyl aminopeptidase I) lies within this interval. We defined the genomic structure of CTSC and found mutations in all eight families. In two of these families we used a functional assay to demonstrate an almost total loss of cathepsin C activity in PLS patients and reduced activity in obligate carriers.

P-glycoprotein and cytochrome P-450 3A inhibition: dissociation of inhibitory potencies.

Many P-glycoprotein (P-gp) inhibitors studied in vitro and in vivo are also known or suspected to be substrates and/or inhibitors of cytochrome P-450 3A (CYP3A). Such overlap raises the question of whether CYP3A inhibition is an intrinsic characteristic of P-gp inhibitors, a matter of concern in the development and rational use of such agents. Thus, the purpose of the present study was to determine whether the ability to inhibit P-gp and CYP3A is, in fact, linked and whether specific P-gp inhibitors with limited ability to inhibit CYP3A can be identified. Therefore, the potency of a series of 14 P-gp inhibitors was assessed by measuring their inhibition of the transepithelial flux across Caco-2 cells of digoxin, a prototypical P-gp substrate. CYP3A inhibition was determined from the impairment of nifedipine oxidation by human liver microsomes. Determination of the apparent Ki values for CYP3A inhibition and the IC50s for P-gp and CYP3A inhibition allowed comparison of the relative inhibitory potency of the compounds on the two proteins' function. The IC50s for P-gp inhibition ranged from 0.04 to 3.8 microM. All compounds inhibited CYP3A with apparent Ki values of between 0.3 and 76 microM and IC50s between 1.5 and 50 microM. However, no correlation was found between the extent of P-gp inhibition and CYP3A inhibition, and the ratio of the IC50 for CYP3A inhibition to the IC50 for P-gp inhibition varied from 1.1 to 125. These results demonstrate that, although many P-gp inhibitors are potent inhibitors of CYP3A, a varying degree of selectivity is present. The development and use of P-gp inhibitors with minimal or absent CYP3A inhibitory effects should decrease the impact of drug interactions on the therapeutic use of such compounds.

Expressed sequence tags (ESTs) from desiccated Tortula ruralis identify a large number of novel plant genes.

The desiccation-tolerant moss Tortula ruralis [Hedw.] Gaerten., Meyer & Scherb. has both a constitutive protection system and an active rehydration induced recovery mechanism apparently unique to bryophytes. Immediately following rehydration, desiccated T.ruralis gametophytes produce a set of polypeptides whose synthesis is unique to the rehydrated state. We report the construction of a cDNA expression library from the polysomal mRNA of desiccated gametophytes and the single-pass sequencing of randomly selected clones. 152 expressed sequence tags (ESTs) were generated representing more than 60,000 bp of non-redundant DNA sequence. 44 ESTs (29%) demonstrated significant homology to previously identified nucleotide and/or polypeptide sequences, such as ribosomal proteins, desiccation-related peptides, early light-inducible proteins and a V-type ATPase. Analysis of a subset of these homologous ESTs reveals that codon preference in T.ruralis is similar to that of vascular plants, particularly the Magnoliopsida. 108 ESTs (71%) demonstrated no significant homology to deposited sequences and represent a large number of novel plant genes. Analysis of these ESTs will define the range of genes involved in cellular repair and recovery and may provide greater insight to the complex phenotype of vegetative desiccation-tolerance.

Cigarette smoke potentiates house dust mite allergen-induced increase in the permeability of human bronchial epithelial cells in vitro.

Although studies have suggested that exposure to cigarette smoke (CS) may be associated with the development of atopy, the mechanisms underlying this are not clearly understood. It has been suggested that CS impairs the barrier function of the airway epithelium, leading to increased access of allergens such as those of the house dust mite (HDM) Dermatophagoides pteronyssinus (Der p) to antigen-presenting cells, with subsequent allergic sensitization. In order to test this hypothesis, we established primary explant cultures of human bronchial epithelial cells (HBEC) in cell culture inserts, and exposed these for 20 min, 1 h, 3 h, and 6 h to CS or air in the absence or presence of 300 ng/ml Der p, and then further incubated the cultures over a period of 24 h. The HBEC cultures were assessed for changes in permeability as measured by changes in: (1) electrical resistance (ER); and (2) passage of 14C-labeled bovine serum albumin (14C-BSA) and Der p allergens across the HBEC cultures. We also assessed the effects of protease inhibitors and the antioxidant glutathione (GSH) in this experimental system. Damage to HBEC cultures was assessed by the release of [51Cr]sodium chromate from prelabeled cells, and by release of lactate dehydrogenase (LDH). Twenty minutes of exposure to CS as compared with exposure to air did not significantly alter either the ER or passage of 14C-BSA across the HBEC cultures. In contrast, incubation with Der p led to a significant increase in the permeability of HBEC cultures, an effect that was enhanced by exposure to CS but was abrogated by the specific protease inhibitors and GSH. Passage of Der p was also increased by exposure to CS. Exposure of HBEC cultures to CS led to a significant release of 51Cr and LDH from these cells as compared with cells exposed to air. This effect was augmented further when HBEC cultures were incubated with Der p. Exposure of HBEC cultures for 1 h, 3 h, and 6 h to CS led to a markedly significant dose- and time-dependent increase in the permeability of these cells. These results suggest that exposure to CS significantly enhances Der p-induced decreases in electrical resistance and the increased passage across HBEC cultures of 14C-BSA and of the Der p allergen itself.

Absence of prolactin gene expression in colorectal cancer.

AIMS: Previous studies documenting hyperprolactinaemia in patients with colorectal cancer have suggested that the tumour is the source of hormone production. The aim of this study was to determine the frequency of hyperprolactinaemia in patients with colorectal cancer before, during, and after surgery, and also to determine whether prolactin is produced by these tumours. METHODS: Serum prolactin concentrations were measured in 20 patients with colorectal cancer before, during, and after surgical resection of their tumours. Samples taken during surgery included peripheral venous blood and blood taken from the main veins draining the tumour. To determine whether the tumour was responsible for the production of prolactin in these patients, paraffin wax embedded sections of tumour specimens were subjected to immunohistochemistry and western blotting using a monoclonal antibody to prolactin. RESULTS: Five patients (three women, two men) had preoperative prolactin concentrations above the normal reference range, although this increase was of clinical importance in only two. After surgical resection of their tumours, prolactin concentrations remained high in both patients. All 20 patients had greatly raised prolactin values at the time of surgery, irrespective of whether this was measured in peripheral blood or in blood taken from veins draining the tumour. All 20 colorectal cancer tissue samples, including those with raised preoperative and/or postoperative prolactin concentrations, were negative for prolactin staining. Frozen tissue was also available in four cases. The absence of prolactin gene expression in these four tumours was confirmed both by repeat immunohistochemistry and by western blotting. A further 50 colorectal cancer cases examined by immunohistochemistry alone were also unreactive for prolactin. CONCLUSIONS: The results of this study suggest that serum prolactin concentrations may occasionally be raised in colorectal cancer patients, but that the tumour is not the source of hormone production.

Coadministration of glyburide and minoxidil, drugs with opposing effects on potassium channels.

INTRODUCTION: Adenosine triphosphate (ATP)-sensitive potassium (K+) channels are modulated by drugs, so that they are opened by vasodilators such as minoxidil but are closed by hypoglycemic agents such as glyburide (glibenclamide). Animal studies and in vitro evidence suggests that the coadministration of drugs with opposing effects on K+ channels attenuates their pharmacodynamic effects. METHODS: To investigate whether this important pharmacodynamic interaction occurs in humans, we administered 5 mg minoxidil, 2.5 mg glyburide or both in a double-blind fashion to nine healthy subjects. Glucose and insulin responses during an intravenous glucose tolerance test (0.3 gm/kg) were measured and blood pressure was recorded for 8 hours. In an additional four subjects the effect of 5 mg glyburide on the hypotensive effect of 5 mg minoxidil was examined. RESULTS: None of the parameters of glucose metabolism differed significantly when subjects received glyburide alone, minoxidil alone, or glyburide with minoxidil. Minoxidil or minoxidil in combination with 2.5 mg glyburide resulted in a similar significant decrease in blood pressure compared with the response to glyburide alone. The hypotensive effect of minoxidil was smaller in the four subjects who received the higher dose of glyburide, but significant hypoglycemia (blood glucose concentration < 60 mg/dl) occurred in three of the four subjects. CONCLUSION: We conclude that, in healthy volunteers, the coadministration of 2.5 mg glyburide and 5 mg minoxidil does not result in attenuation of the blood pressure-lowering effect of minoxidil. The smaller hypotensive response in four subjects who received 5 mg glyburide and 5 mg minoxidil suggests the possibility of a dose-related drug interaction. Studies with strict clamping of blood glucose concentrations will be required to address this possibility.

Microsomal codeine N-demethylation: cosegregation with cytochrome P4503A4 activity.

Codeine is metabolized by glucuronidation, by O-demethylation to morphine, and by N-demethylation to norcodeine. The enzyme responsible for the O-demethylation to morphine has been identified as cytochrome P4502D6 (CYP2D6). The purpose of the present study was to identify the specific P450 enzyme responsible for codeine N-demethylation. Microsomal preparations (250 pmol of P450) obtained from 12 human liver donors were incubated with 20 microM codeine and analyzed for norcodeine formation. Codeine N-demethylation activity was linearly correlated with nifedipine oxidation activity (r = 0.90, p < 0.001), a marker of CYP3A4, but not with codeine O-demethylation, a marker of CYP2D6. Preincubation with troleandomycin (50 microM), or gestodene (50 microM) inhibitors of CYP3A4, decreased the rate of production of norcodeine by 60 and 45% compared to control values, respectively. Similarly, ketoconazole (10 microM) and erythromycin (10 microM) inhibited codeine N-demethylation by 75 and 35%, respectively. In contrast, the presence of quinidine, sulfaphenazole, or diethyldithiocarbamate in the incubation mixture had no effect on norcodeine formation. Preincubation with antibodies raised to CYP3A4 (5 mg lgG/nmol P450) caused 96% inhibition of norcodeine production, whereas preimmune IgG or antibodies raised to CYP2A6 and CYP2C had no effect. Additionally, significant norcodeine production was observed with purified CYP3A4 derived from human liver microsomes. In conclusion, codeine N-demethylation activity cosegregates with CYP3A4 activity. Coadministration of codeine with selective inhibitors of CYP3A4 may result in increased morphine production and enhanced pharmacodynamic effects due to shunting down the CYP2D6 pathway.