Are frequent short gastro-oesophageal reflux episodes the cause of symptoms in patients with non-ulcer dyspepsia responding to treatment with ranitidine?

BACKGROUND: Patients with non-ulcer dyspepsia (NUD) responding to treatment with H2-receptor antagonists have no clinically useful characteristics. This trial compares the gastro-oesophageal reflux pattern as measured by 24-h oesophageal pH monitoring in patients responding to ranitidine with that of non-responders. METHODS: Thirty-one patients with NUD were randomized to 6 weeks' double-blind alternating treatment with 150 mg ranitidine twice daily or placebo and classified as responders or non-responders. RESULTS: Pathologic gastro-oesophageal reflux was seen in 3 of the 13 responders and 4 of the 18 no-responders (NS). The responders had frequent short reflux episodes (< 1 min in duration). When 4 patients with > or = 5 reflux episodes longer than 5 min were excluded, the number of short reflux episodes (median) in responders and non-responders was 32 and 14, respectively. The difference is statistically significant (p = 0.025). There were no other differences between the groups. CONCLUSIONS: In this study patients with NUD responding to ranitidine were characterized by frequent short reflux episodes in the absence of numerous long reflux episodes.     

Treating the symptoms of gastro-oesophageal reflux disease: a double-blind comparison of omeprazole and cisapride

BACKGROUND: Few studies have specifically addressed the management of the symptoms of gastro-oesophageal reflux disease, and there are no comparative data in this respect for acid pump inhibitors and prokinetic agents. METHODS: Following endoscopy 424 patients presenting with heartburn as the predominant symptom of gastro-oesophageal reflux disease were randomized to treatment with omeprazole 20 or 10 mg once daily, or cisapride 10 mg four times daily, in a double-blind, double-dummy, parallel group, multicentre study. Symptoms and quality of life were assessed at 4 weeks. Patients still experiencing heartburn continued therapy for a further 4 weeks and the assessments were repeated. RESULTS: At 4 weeks, heartburn was resolved in 65% (95% CI: 57-73%), 56% (48-64%) and 41% (32%-49%) of patients treated, respectively, with omeprazole 20 mg and 10 mg once daily, and cisapride. Both omeprazole doses were significantly more effective than cisapride (P < 0.01). The same order of efficacy was observed regardless of the presence of erosive oesophagitis. Regurgitation and epigastric pain also improved to a greater degree with omeprazole than with cisapride. Quality of life was improved in all treatment groups, and the improvement in the reflux dimension of the Gastrointestinal Symptom Rating Scale (GSRS) score was significantly different between groups (P = 0.002). CONCLUSIONS: Omeprazole 20 or 10 mg once daily is significantly more effective than cisapride in the resolution of heartburn, regardless of the presence of erosive oesophagitis, and this is accompanied by an improvement in patient quality of life.     

Early evening dosing of ranitidine. Comparison with nighttime dosing of ranitidine or cimetidine in duodenal ulceration

A double-blind multinational comparison of ranitidine 300 mg post evening meal (pem), ranitidine 300 mg nocte and cimetidine 800 mg nocte has been carried out in 1677 patients with endoscopically verified duodenal ulcer disease. Fifty-three percent of ulers healed by two weeks during treatment with ranitidine 300 mg pem and 88% by four weeks, while the results for ranitidine 300 mg nocte were 50% and 86%, respectively, and 44% and 84% for cimetidine. The difference between ranitidine 300 mg pem and cimetidine was significant at two weeks (P = 0.002, Mantel-Haenszel chi-squared test). The relative efficacy of the treatments was not dependent upon gender, smoking habit, alcohol intake, or ulcer frequency. However, the overall differences in healing between patients with small and large ulcers and patients with single and multiple ulcers were significantly different at weeks 2 and 4 (P < 0.001). Significantly more patients treated with ranitidine (60%) had complete relief of epigastric pain than those treated with cimetidine (54%) (P < 0.05). A meta-analysis of the four double-blind comparisons of ranitidine 300 mg pem (N = 841) and 300 mg nocte (N = 849), including the present study, failed to show the benefits of pem dosing, predicted from pharmacological studies.     

Sleep-related gastro-oesophageal reflux: provocation with a late evening meal and treatment with acid suppression

BACKGROUND: Two studies were carried out in order to investigate the issue of meal-provoked nocturnal gastrooesophageal reflux. METHODS: In Experiment 1, 20 symptomatic reflux patients underwent both pH and polysomnographic monitoring on two nights. On one night, patients ate a non-provocative meal prior to 19.00 hours, while on the other night patients consumed a late evening meal (21.00 hours). In Experiment 2.17 symptomatic reflux patients were studied using pH and polysomnographic monitoring on two nights subsequent to a late evening provocative meal. On one night, patients received 75 mg of the H2-antagonist ranitidine, while on another night they received a placebo. The data from 12 of the 17 patients studied were used in the analysis. RESULTS: For Experiment 1, no significant differences in the number or duration of reflux events, acid exposure (total %), or polysomnographic measures of per cent of sleep stages between the two nights were observed. The results of the second experiment demonstrated that when given ranitidine, patients experienced significant decrease in acid contact time (total %), and mean duration of reflux events. Subjective reports of discomfort and sleep disturbance were also significantly improved on the drug night. However, significant differences in polysomnographic measures were not observed. CONCLUSIONS: Based on these results, we conclude that in some symptomatic reflux patients a late-night non-provocative meal may not increase the incidence of gastro-oesophageal reflux, and that a low dose of an H2-antagonist is effective in decreasing oesophageal acid contact time following a late evening provocative meal.     

One-year prophylactic efficacy and safety of pantoprazole in controlling gastro-oesophageal reflux symptoms in patients with healed reflux oesophagitis

BACKGROUND: Pantoprazole is a benzimidazole derivative which selectively inhibits the proton pump H+. K+-ATPase necessary for the final step in gastric acid secretion. AIM: To investigate the tolerability and the prophylactic effect of pantoprazole 40 mg once daily on relapse in patients whose reflux oesophagitis had been healed. METHODS: The safety of pantoprazole 40 mg once daily was assessed in an open 1-year trial on 222 patients whose reflux oesophagitis had been healed with omeprazole or pantoprazole. Relapse was defined as endoscopically-confirmed reflux oesophagitis (at least Grade I), with endoscopies being performed for patients experiencing 3 consecutive days of disease-specific symptoms. RESULTS: Kaplan-Meier survival analysis at 6 and 12 months gave estimated treatment failure rates of 2% and 6% from confirmed relapses (per-protocol), and of 9% and 30% for a worst-case group (all withdrawals counted as failures). The only population shift in laboratory variables was a doubling of the median serum gastrin level over the first 6 months; thereafter it stabilized. Fifty-four (24%) patients experienced adverse events; 15 of these withdrew. Serious adverse events were reported for 12 patients. CONCLUSIONS: Pantoprazole appears to be highly effective and to have a good safety profile for long-term prophylaxis of reflux oesophagitis.     

A comparison of ranitidine, droperidol or placebo in the prevention of nausea and vomiting after hysterectomy

Surgical procedures including the extent of systematic lymphadenectomy are still under discussion in the treatment of esophageal cancer. In the own patients' population 92 subtotal en bloc-esophagectomies with a standard two field lymphadenectomy were performed. A total of 1483 lymph nodes were resected in the thoracic and abdominal compartments with an incidence of 16.1% being metastatic. Stage pN1 disease occurred in 57.6% of the patients. The median number of lymph nodes resected in each specimen was 16, independent of tumor stage, -site or R-classification. The number of infiltrated nodes increased with tumor stages. R-classification, tumor stage and number of involved lymph nodes could be analyzed as prognostic factors. After R0-resection a median survival rate of 25.4 months could be achieved, following pN0-stage that of 27.4 months. In case of two metastatic lymph nodes the prognosis decreased significantly to 14.4 months (p < 0.01). Therefore, two field lymphadenectomy may show a therapeutic benefit only in a subgroup of patients with a limited number of lymph nodes infiltrated.     

Omeprazole 10 milligrams once daily, omeprazole 20 milligrams once daily, or ranitidine 150 milligrams twice daily, evaluated as initial therapy for the relief of symptoms of gastro-oesophageal reflux disease in general practice

BACKGROUND: The efficacy of omeprazole, 20 mg once daily, in the treatment of reflux oesophagitis and the therapeutic advantages over the histamine H2 receptor antagonists are well documented. This study assessed 20 mg omeprazole daily (OM20), 10 mg omeprazole daily (OM10), and 150 mg ranitidine (RAN) twice daily for symptom relief in gastro-oesophageal reflux disease (GORD). METHODS: Patients (n = 994) presenting with heartburn to their general practitioner underwent endoscopy to exclude peptic ulcer disease and were randomized into a UK, multicentre, parallel-group, double-blind comparison of the three treatments for 4 weeks. Symptoms were assessed at clinic visits after 2 and 4 weeks. RESULTS: Symptom relief after 4 weeks was achieved by 61% (OM20), 49% (OM10), and 40% (RAN) patients (OM20 versus OM10, P < 0.0167; OM20 versus RAN, P < 0.0001; OM10 versus RAN, P < 0.01). Among the patients (32%) with erosive reflux oesophagitis, symptom relief was achieved in 79% (OM20), 48% (OM10), and 33% (RAN) (OM20 versus OM10, P < 0.0001; OM20 versus RAN, P < 0.0001; OM1O versus RAN, NS). CONCLUSION: Omeprazole, 20 mg, is the most effective initial therapy for relief of GORD symptoms.     

Double blind cross-over placebo controlled study of omeprazole in the treatment of patients with reflux symptoms and physiological levels of acid reflux--the "sensitive oesophagus"

We describe the case of a 70-year-old woman admitted to our hospital because of anemia and hepatomegaly. Imaging studies (ultrasound and CT scan) revealed a tumor in the liver. The patient developed consumption coagulopathy and died. Postmortem examination revealed hepatic angiosarcoma. The pathophysiology of disseminated intravascular coagulation associated with vascular tumors and abnormalities of blood coagulation in patients with cancer is discussed.     

Treatment of reflux oesophagitis of moderate and severe grade with ranitidine or pantoprazole--comparison of 24-hour intragastric and oesophageal pH

BACKGROUND: Proton pump inhibiting drugs strongly decrease gastric acid secretion and have proven more effective in the treatment of reflux oesophagitis than H2-receptor antagonists. METHODS: In a double-blind randomized trial, 24 patients with oesophagitis grade II (n = 15) and III (n = 9) were treated for 4 weeks with either ranitidine 150 mg b.d. (n = 13) or pantoprazole 40 mg o.m. (n = 11). Before the trial and on the last day of medication, 24-h intragastric pH and oesophageal pH profiles were performed. Healing was assessed by endoscopy. RESULTS: Pantoprazole increased median gastric pH from 1.7 to 3.9. Virtually no change in gastric pH was seen in the ranitidine group. Pantoprazole reduced the fraction time of pH < 4 in the oesophagus from 21% to 3% (P = 0.0005), and the median number of refluxes from 206 to 56 (P = 0.022). Oesophageal acid exposure was not decreased by ranitidine. Healing of the oesophagitis was seen in 6/11 cases after pantoprazole and in 3/13 cases after ranitidine (N.S.) CONCLUSION: In patients with oesophagitis of moderate and severe grade, pantoprazole 40 mg o.m. decreases intragastric acidity and gastro-oesophageal acid reflux more effectively than ranitidine 150 mg b.d.     

A double-blind, controlled comparison of the novel antipsychotic olanzapine versus haloperidol or placebo on anxious and depressive symptoms accompanying schizophrenia

BACKGROUND: Depressive symptoms are a common feature of schizophrenia and may represent a core part of the illness. Where present, it has been associated with greater overall morbidity and mortality. Monotherapy with conventional dopamine antagonists may either worsen or bestow a limited therapeutic benefit. Accordingly the use of adjunctive thymoleptics has been explored. In contrast, olanzapine (OLZ), an atypical antipsychotic agent, offers a distinctive and pleotropic pharmacology suggestive of a broader efficacy profile than conventional neuroleptic agents. METHODS: In a 6-week placebo- and haloperidol (HAL)-controlled trial with 335 randomized subjects with chronic schizophrenia in an acute exacerbation, three fixed dose ranges of OLZ (5, 10, or 15 +/- 2.5 mg) were evaluated versus HAL (10-20 mg) or placebo. RESULTS: Baseline to endpoint change in the Brief Psychiatric Rating Scale including the anxiety-depression cluster (items 1, 2, 5, 9) was analyzed. Two dose ranges of OLZ (10 +/- 2.5, 15 +/- 2.5) were superior to placebo (p < 05) in improving mood status, whereas HAL was not. CONCLUSION: Contributions from a more selective mesolimbic dopaminergic profile, D1 or D4 activity, the release of dopamine/norepinephrine in the prefrontal cortex, and/or serotonin 5-HT2A,C antagonism may explain the differential benefit seen with OLZ in the treatment of comorbid anxious and depressive symptoms in schizophrenia.     

Meta-analysis of prophylactic or empirical antifungal treatment versus placebo or no treatment in patients with cancer complicated by neutropenia

OBJECTIVE: To determine whether antifungal agents given prophylactically or empirically decrease morbidity and mortality in patients with cancer complicated by neutropenia. DESIGN: Meta-analysis of randomised trials of amphotericin B, various lipid soluble formulations of amphotericin B (for example, AmBisome), fluconazole, ketoconazole, miconazole, or itraconazole compared with placebo or no treatment. SETTING: Trials conducted anywhere in the world. SUBJECTS: Patients with cancer complicated by neutropenia. MAIN OUTCOME MEASURES: Mortality, invasive fungal infection (defined as positive blood culture, oesophageal candidiasis, or lung or deep tissue infection), and colonisation. RESULTS: 24 trials with 2758 randomised patients were reviewed; the total number of deaths was 434. Prophylactic or empirical treatment with antifungals as a group bad no effect on mortality (odds ratio 0.92; 95% confidence interval 0.74 to 1.14). Amphotericin B decreased mortality significantly (0.58; 0.37 to 0.93) but the studies were small and the difference in number of deaths was only 15. Antifungal treatment decreased the incidence of invasive fungal infection (0.47; 0.35 to 0.64) and fungal colonisation (0.45; 0.30 to 0.69). For every 73 patients treated (95% confidence interval to 48 to 158) one case of fungal invasion was prevented in surviving patients. CONCLUSIONS: There seems to be no survival benefit of antifungal agents given prophylactically or empirically to patients with cancer complicated by neutropenia. These agents should be restricted to patients with proved infection and those in randomised trials. A large, definitive placebo controlled trial of amphotericin B is needed.     

Omeprazole and ranitidine in long-term treatment of duodenal ulcer: a double-blind comparison of length of time in remission

In most patients duodenal ulcer is a chronic relapsing disease. If no active maintenance treatment or eradication therapy is given after healing, around 70-100% of patients have a relapse during the first year. We conducted a double-blind multicenter study in 472 patients with duodenal ulcer. They were treated with omeprazole 20 mg every morning for four or eight weeks and when healed were randomly allocated to maintenance treatment with either omeprazole 20 mg every morning or ranitidine 150 mg at bedtime for up to six months. The patients were assessed by endoscopy at monthly intervals until healing occurred. Thereafter scheduled endoscopy was carried out after 1, 3, and 6 months of maintenance treatment or immediately in the event of a suspected relapse. Healing status (intention to treat approach) was 87% at four weeks and 93% at eight weeks. At six months the estimated remission rate was 90% for omeprazole and 82% for ranitidine (P = 0.03, 95% CI 1-15%). The incidence of adverse events was similar during the two maintenance treatments. Treatment with omeprazole 20 mg every morning maintained significantly more patients in remission than treatment with ranitidine 150 mg at bedtime.     

rhuIL-2 adjunctive therapy in multidrug resistant tuberculosis: a comparison of two treatment regimens and placebo

SETTING: Low-dose recombinant human interleukin 2 (rhuIL-2) adjunctive immunotherapy in multidrug resistant tuberculosis (MDR-TB) patients. OBJECTIVE: Evaluation of the effects of daily versus pulse-administered rhuIL-2 compared to placebo. DESIGN: MDR-TB patients on best available antituberculous chemotherapy received rhuIL-2 for 30 consecutive days (daily therapy), or for 5 days followed by a 9-day 'rest', for three cycles (pulse therapy). Placebo control patients received diluent. The cumulative total dose of rhuIL-2 given to each patient in either rhuIL-2 treatment group was the same. Patient immunologic, microbiologic, and radiologic responses were compared. RESULTS: The three treatment schedules induced different results. Immune activation was documented in patients receiving daily rhuIL-2 therapy. Numbers of CD25+ and CD56+ cells in the peripheral blood were increased in these patients, but not in patients receiving pulse rhuIL-2 or placebo. In addition, 5/8 (62%) patients receiving daily rhuIL-2 demonstrated reduced or cleared sputum bacterial load while only 2/7 (28%) pulse rhuIL-2 treated and 2/8 (25%) controls showed bacillary clearance. Chest radiographs of 7/12 (58%) patients receiving daily rhuIL-2 indicated significant improvement over 6 weeks. Only 2/9 (22%) pulse rhuIL-2-treated patients and 5/12(42%) placebo controls showed radiologic improvement. CONCLUSION: Daily low dose rhuIL-2 adjunctive treatment stimulates immune activation and may enhance the antimicrobial response in MDR-TB.     

Pentoxifylline versus placebo in the treatment of infertility associated with minimal or mild endometriosis: a pilot randomized clinical trial

The long-term outcome of pulmonary function was evaluated in farmer's lung (FL) patients compared to representative control farmers. This is, to our knowledge, the first such study which has included a control group. Clinical examinations were conducted in 89 FL patients and 84 control farmers, matched by age, sex, and smoking habits. The mean time after the first diagnosed episode of FL was 14 yrs. The mean transfer factor of the lung for carbon monoxide (TL,CO) was on average 12% lower (p < 0.001) in FL patients compared to control farmers. In spirometry, the mean maximum expiratory flow at 50% of vital capacity (MEF50) was lower (p = 0.08) in FL patients but there were no differences in mean vital capacity (VC) or forced expiratory volume in one second (FEV1) between FL patients and control farmers. However, airway obstruction, defined as an FEV1/VC less than 88% of predicted, was more common in FL patients than in control farmers (33 versus 17%; p = 0.02). Patients who had had recurrent episodes of FL had a significantly lower mean TL,CO compared to those FL patients who had experienced only a single episode. In conclusion, impairment of the pulmonary transfer factor is the most important long-term consequence of farmer's lung. However, farmer's lung may also lead to development of airway obstruction.     

No effects of high-dose omeprazole in patients with severe airway hyperresponsiveness and (a)symptomatic gastro-oesophageal reflux

Uptake of inhaled anesthetics may be measured as the amount of anesthetic infused to maintain a constant alveolar concentration of anesthetic. This method assumes that the patient absorbs all of the infused anesthetic, and that none is lost to circuit components. Using a standard anesthetic circuit with a 3-L rebreathing bag simulating the lungs, and simulating metabolism by input of carbon dioxide, we tested this assumption for halothane, isoflurane, and sevoflurane. Our results suggest that after washin of anesthetic sufficient to eliminate a material difference between inspired and end-tidal anesthetic, washin to other parts of the circuit (probably the ventilator) and absorbent (soda lime) continued to remove anesthetic for up to 15 min. From 30 min to 180 min of anesthetic administration, circuit components absorbed trivial amounts of isoflurane (12 +/- 13 mL vapor at 1.5 minimum alveolar anesthetic concentration, slightly more sevoflurane (39 +/- 15 mL), and still more halothane (64 +/- 9 mL). During this time, absorbent degraded sevoflurane (321 +/- 31 mL absorbed by circuit components and degraded by soda lime). The amount degraded increased with increasing input of carbon dioxide (e.g., the 321 +/- 31 mL increased to 508 +/- 48 mL when carbon dioxide input increased from 250 mL/min to 500 mL/min). Measurement of anesthetic uptake as a function of the amount of anesthetic infused must account for these findings. Implications: Systems that deliver inhaled anesthetics may also remove the anesthetic. Initially, anesthetics may diffuse into delivery components and the interstices of material used to absorb carbon dioxide. Later, absorbents may degrade some anesthetics (e.g., sevoflurane). Such losses may compromise measurements of anesthetic uptake.     

Comparison of methotrexate 30 mg per week with placebo in chronic steroid-dependent asthma: a 12-week double-blind, cross-over study

Methotrexate has been shown to have a steroid-sparing effect in chronic steroid-dependent asthmatics at a dose of 15 mg week-1. The aim of this study was to investigate the steroid-sparing activity and adverse events profile of methotrexate 30 mg week-1 in severe steroid-dependent asthma. Eighteen patients who had required 10-50 mg week-1 prednisolone for at least 6 months were asked to participate in a randomized, double-blind, placebo-controlled cross-over study lasting 24 weeks. Daily diary cards of symptoms, peak expiratory flow rate and medication requirements were kept and the patients attended for a chest X-ray, spirometry, lung volumes and gas transfer at commencement and after each 12-week treatment period. Every 3 weeks, adverse events were noted and blood taken for full blood count, urea and electrolytes and liver function tests. Twelve patients completed the trial. Withdrawals were due to non-compliance in two patients, pneumonia in two patients, depression in one patient (on placebo) and severe nausea in one patient. Adverse events were common, probably as a consequence of the higher dosage. Prednisolone requirements were not significantly reduced on methotrexate. Lung function improved on methotrexate with a significant rise in maximal mid-expiratory flow rate and a trend towards improvement in FEV1.     

Adolescents with active or inactive epilepsy or asthma: a comparison of quality of life

PURPOSE: We compared quality of life (QOL) in youth with inactive or active epilepsy with that of a similar sample of youth with asthma. We explored 19 different dimensions in three domains (psychological, social, and school) and also determined differences related to illness severity and gender. METHODS: Subjects were 228 adolescents (117 with epilepsy and 111 with asthma). Data were collected from clinic records and from the adolescents, their mothers, and their teachers through questionnaires and structured interviews. Data were analyzed by analysis of covariance. RESULTS: The analysis with all 19 QOL variables indicated a significant difference between the total asthma and the total epilepsy samples (multivariate F = 3.36, p = 0.0001). Further evaluation reflected differences between the epilepsy group and the asthma group on 13 of the 19 QOL variables. When active and inactive epilepsy and asthma groups were compared, youth with active epilepsy were faring worse than all other groups in 10 areas. Moreover, youth with inactive epilepsy were faring worse than those with inactive asthma in four areas. Illness severity and sex differences were more strongly related to QOL in the epilepsy sample than in the asthma sample. Sex-severity interactions suggested that girls with high seizure severity were most at risk for QOL problems. CONCLUSIONS: Youth with active epilepsy generally had the poorest QOL. Severe seizures and female sex were associated with more problems. Sex-severity interactions should be explored in future research.     

Two year maintenance treatment of duodenal ulcer disease with ranitidine 150 mg: a prospective multicentre randomised study. GEMUD (Groupe d'Etude de la Maladie Ulcéreuse Duodénale)

Maintenance treatment of duodenal ulcer (DU) with ranitidine 150 mg/day was compared with placebo in a two year prospective multicentre randomised study. Three hundred and ninety nine patients were included (mean age: 44.7 years, M/F ratio = 2.47/1; 37.6% of smokers) in placebo (n = 202) and ranitidine (n = 197) groups. Efficacy was assessed by the length of time to the first ulcer pain attack (with or without endoscopic confirmation) or DU complication. One hundred and fourteen patients of 399 (28.6%) had incomplete follow up. Actuarial survival curves of patients without ulcer pain (26 and 53% at two years in placebo and ranitidine groups, respectively) were significantly different (p < 0.0001). Endoscopies were performed depending on physicians' decision (mainly where there was severe pain or complication). Patients without relapses from endoscopy were more frequent in the ranitidine group (83%) than in the placebo group (47%, p < 0.0001). A greater incidence of complications, mainly bleeding, was also seen in the placebo group (13 complications v two in the ranitidine group, p < 0.002). No factor predicting DU relapse was identified. No important side effect was encountered. Ranitidine 150 mg/day is effective and well tolerated in preventing ulcer pain attacks and DU complications for up to two years.     

A comparison of fluticasone propionate, 1 mg daily, with beclomethasone dipropionate, 2 mg daily, in the treatment of severe asthma. International Study Group

Cytochrome P450 1A1 was localized immunohistochemically and benzo[a]pyrene hydroxylase activity was identified in situ by means of fluorescence histochemistry in the nasal mucosa of untreated, 3-methylcholanthrene-treated or Aroclor 1254-treated rats. Cytochrome P450 1A1 was localized predominantly within Bowman's glands, with considerably less staining occurring in the olfactory epithelium of untreated rats. Similarly, benzo[a]pyrene was hydroxylated to the greatest extent in Bowman's glands and, to a lesser extent, in olfactory epithelial cells. Pre-treatment of tissue sections of nasal mucosa with anti-P450 1A1 inhibited most of the benzo[a]pyrene hydroxylase activity present. Although 3-methylcholanthrene treatment did not affect either cytochrome P450 1A1 or hydroxylase activity in the nasal mucosa, a single intraperitoneal injection of Aroclor 1254 significantly increased anti-P450 1A1 binding in Bowman's glands and in the olfactory and respiratory epithelia, and dramatically enhanced benzo[a]pyrene hydroxylase activity in the epithelia and the subepithelial ducts and glands in both the olfactory and respiratory regions. In contrast to its effects on cytochrome P450 1A1, Aroclor 1254 produced a considerably greater induction of hydroxylase activity in the respiratory region, especially in the seromucous glands, than in the olfactory region. These results suggest that Aroclor 1254 treatment also induces other forms of cytochrome P450 in the respiratory region of the nasal mucosa.