Evaluation of the Xpa-Deficient Transgenic Mouse Model for Short-Term Carcinogenicity Testing: 9-Month Studies with Haloperidol, Reserpine, Phenacetin, and D-Mannitol

As part of the international evaluation program coordinated by ILSI/HESI, the potential of DNA repair deficient Xpa- /- mice and the double knockout Xpa- /- .p53+ /- mice for short term carcinogenicity assays was evaluated. For comparison also wild-type C57BL/6 mice (WT) were included in these studies. Four test compounds were administered to groups of 15 male and 15 female Xpa- /- mice, Xpa- /- .p53+ /- mice and WT mice for 39 weeks. The model compounds investigated were haloperidol, reserpine (nongenotoxic rodent carcinogens, putative human noncarcinogens), phenacetin (genotoxic rodent carcinogen, suspected human carcinogen), and D-mannitol (noncarcinogen in rodents and humans). The test compounds were administered as admixture to rodent diet at levels up to 25 mg/kg diet for haloperidol, 7.5 mg/kg diet for reserpine, 0.75% for phenacetin, and 10% for D-mannitol. These levels included the maximum tolerable dose (MTD). Survival was not affected with any of the test compounds. Haloperidol, reserpine and D-mannitol were negative in the carcinogenicity assay with Xpa- /- and Xpa- /- .p53+ /- mice, showing low and comparable tumor incidences in controls and high-dose animals. The results obtained with phenacetin may be designated equivocal in Xpa- /- .p53+ /- mice, based on the occurrence of a single rare tumor in the target organ (kidney) accompanied by a low incidence of hyperplastic renal lesions and a high incidence of karyomegaly. These results are in agreement with the currently known carcinogenic potential of the 4 test compounds in humans.

Turpentine oil induced inflammation decreases absorption and increases distribution of phenacetin without altering its elimination process in rats

Plasma concentrations and pharmacokinetics of phenacetin, a CYP1A2 substrate were determined in normal and experimentally induced inflamed rats by turpentine oil to know the role of inflammation on the pharmacokinetics of phenacetin and formation of its active metabolite (paracetamol) by CYP1A2 in wistar albino rats, weighing about 200-250 g that were randomly divided into two groups consisting six in each group. Rats in group I (control) received phenacetin (150 mg kg(-1), PO) where as group II received phenacetin 12 h after induction of inflammation by turpentine oil (0.4 mL, i.m). Blood samples were collected from retro orbital plexus at pre-determined time intervals prior to and at 0.166, 0.33, 0.67, 1.5, 2, 4, 8 and 12 h post-administration of phenacetin. Plasma was separated and analyzed for phenacetin and its metabolite paracetamol by HPLC assay. Based on plasma concentrations of phenacetin and its metabolite paracetamol, the pharmacokinetic parameters were determined by compartmental methods. C(max) of phenacetin was significantly (p < 0.01) decreased to 19.50 ± 2.74 μg mL(-1) in inflamed conditions compared to 38.13 ± 2.20 μg mL(-1) obtained in normal rats. Except, for significant (p < 0.001) increase in volume of distribution at steady state (V(dss)) from 2.87 ± 0.37 to 8.03 ± 1.26 L kg(-1) and increased the rate of absorption with shorter absorption half-life (t(1/2ka)) for phenacetin in inflammation. None of the pharmacokinetic parameters of either phenacetin or its metabolite paracetamol were affected. It can be concluded that turpentine oil induced inflammation has no role on the activity of CYP1A2 in rats, as the plasma concentrations and pharmacokinetic parameters of paracetamol were found unaltered.

Changes of panorama in renal disease mortality in Finland after phenacetin restriction

The purpose of the present study was to examine the effect of phenacetin consumption and its restriction on the mortality from nephropathy. Changes in this mortality in Finland during 1951-77 were investigated. The second part of the study was concerned with the frequency of papillary necrosis in cases autopsied in the Department of Medicine, Turku University Central Hospital, during 1952-79. These figures were studied in relation to increased phenacetin consumption after World War II, its restriction in 1962 and its complete banning in 1965. Both the epidemiologic survey of the mortality from nephropathy in Finland and the autopsies showed a clear and strong correlation both with increased phenacetin consumption and with its discontinuation. The banning of phenacetin led within 2-4 years to a decline in the mortality from nephropathy to its pre-phenacetin level.

Identification of phenacetin metabolites in human urine after administration of phenacetin-C2H3: measurement of futile metabolic deacetylation via HPLC/MS-SPE-NMR and HPLC-ToF MS

The metabolism of acetyl-labelled phenacetin-C2H3 was investigated in man following a single (150 mg) oral dose. Urine samples were collected at predose, 0-2 h and >2-4 h post-dose, and samples from each time-point were then analysed directly using 1H-nuclear magnetic resonance (NMR) spectroscopy. The phenacetin metabolites acetaminophen (paracetamol) glucuronide, sulphate and the N-acetyl-L-cysteinyl conjugate were identified by this method, and all showed clear evidence of the loss of the original 2H3-acetyl label and its replacement with 1H3 (futile deacetylation). The observed percentage futile deacetylation by 1H-NMR spectroscopy was measured as approximately 20% in each metabolite (about 2% of the recovered dose). After sample preparation by solid-phase extraction on a C18 solid-phase extraction (SPE) cartridge, further profiling was performed using high-performance liquid chromatography/mass spectrometry-solid-phase extraction-nuclear magnetic resonance (HPLC/MS-SPE-NMR) confirming futile deacetylation had taken place as indicated by NMR spectroscopy on both the isolated acetaminophen glucuronide and L-cysteinyl-metabolites. Additional analysis by high-performance liquid chromatography-time-of-flight mass spectrometry (HPLC-ToF MS) identified further phenacetin metabolites, and from these data the mean percentage of futile deacetylation was measured as 31% +/- 2% for the acetylated phenacetin metabolites. A number of non-acetylated metabolites were also detected in the sample via HPLC-ToF MS. The results showed that phenacetin underwent a transient formation via a number of toxic intermediates to a much greater extent than had been observed in similar studies on acetaminophen. These results may contribute to the understanding of the analgesic nephropathy reported following chronic phenacetin consumption.

Bladder tumor associated with phenacetin abuse: a case report and a review of the literature

We herein report the case of a bladder tumor in an 85-year-old man who had been engaged in phenacetin abuse. He had been taking phenacetin owing to migraine headaches since he was 45 year of age. His total intake of phenacetin was approximately 7.3 to 11.5 kg over a period of years. He visited the Department of Urology in our hospital due to gross hematuria and pain on urination. IVP and a pelvic CT scan revealed a tumor mass on the right lateral wall of the urinary bladder. TUR-BT was performed. A histopathological examination of the resected specimen was diagnosed as urotherial carcinoma, grade 2∼3, pT2N0M0. To our acknowledge, only 24 cases of urotherial tumors owing to phenacetin abuse have been previously reported in the Japanese literature, making this the 25 th such case to be reported in Japan.

Effect of acetaminophen, a cyclooxygenase inhibitor, on Morris water maze task performance in mice

Although the mechanism of action of acetaminophen (AAP) is not fully understood, some studies suggest that AAP and phenacetin (PHE) are selective cyclooxygenase (COX)-3 inhibitors. To examine the participation of COX-3 in memory formation, water maze performance was studied in mice treated with AAP, PHE or other COX inhibitors. Mice received intraperitoneal injections of drugs immediately after each training session. Administration of high-dose AAP [302.3 mg/kg (IC50 for COX-2)] or PHE [179.2 mg/kg (IC50 for COX-2)] and of non-specific (indomethacin: 20 mg/kg) or specific COX-2 (NS-398: 10 mg/kg) inhibitor impaired the performance in hidden platform (HP) not visible platform (VP) tasks, whereas low-dose (15.1 mg/kg) AAP facilitated performance in HP and VP tasks. The facilitation of performance by low-dose AAP was reversed by co-administration with a 5-HT(1/2) receptor antagonist (methysergide: 0.47 mg/kg). The middle-dose [69.5 mg/kg (IC50 for COX-3)] of AAP, the PHE [17.9 mg/kg (IC50 for COX-3)] and a specific COX-1 inhibitor (piroxicam: 10-20 mg/kg) did not influence performance in either task. These results suggest that the memory impairment by high-dose AAP and PHE and facilitation of performance by low-dose AAP could involve endogenous COX-2 and serotonergic neuronal activity, but not COX-3, respectively.

Caffeine as a promoter of analgesic-associated nephropathy--where is the evidence?

Individual groups of nephrologists - in their responsibility for their patients - initiated a most controversial discussion whether or not caffeine - coformulated to analgesics - might initiate or sustain analgesic overdosing. The original sources (data) of such suspicion have got lost during the debate of the last two decades. Therefore, it seemed to be appropriate to investigate the original data background and the reasons why nephrologists started to suspect caffeine as a stimulant of analgesic overdosing by employing a systematic and exhaustive review of primary nephrological publications. Their selection followed a precise selection plan, including all epidemiological studies on analgesic-associated nephropathy, the original papers of all groups having been involved in those studies, further originals from the mainly involved countries (academically, politically), and any literature thereof cited as a proof. The following results emerged from the investigation: (i) The epidemiological studies warranted no conclusion about a role of caffeine in prompting excessive analgesic use. (ii) The identified groups of nephrologists provided not substantial data to advocate the said suspicion, except for the observation of a preferential choice of phenacetin-containing combinations, especially powder preparations. (iii) Only two cited original data sources revealed drug-seeking behaviour with phenacetin-containing preparations which subsided, after phenacetin was banned from the respective markets. Conclusively, it appears that there is no substantial data to support a pivotal role of caffeine in initiating or sustaining analgesic overdosing. However, there is strong data that phenacetin, by its psychotropic properties, may have caused drug-seeking behaviour and thus led to analgesic overdosing. This conclusion is convincingly supported by thorough pharmacokinetic investigations. Note: All caffeine-related statements within the reviewed literature have been collected in tables (referred to as Table SX) which are provided in full text for check on the following website: http://www.blackwellpublishing.com/products/journals/suppmat/FCP/FCP174/FCP174sm.htm

Controlled release from solid dispersion composed of poly(ethylene oxide)-Carbopol interpolymer complex with various cross-linking degrees of Carbopol

Solid dispersion composed of the poly(ethylene oxide) (PEO)-Carbopol((R)) (CP) interpolymer complex containing phenacetin (PHE) was prepared by using six grades of CP having various cross-linking degrees. We attempted to control the medicine release from the PEO-CP solid dispersion by varying the CP grade. The powder X-ray diffraction pattern and differential scanning calorimetry curves suggested that PHE existed in the amorphous state, and PEO in the crystalline state disappeared in the solid dispersions. The release profile of PHE varied depending on the CP grade. A small release rate was observed at CP910 and CP971P that are cross-linked at low and middle degrees, respectively. The Fourier transform-infrared (FT-IR) spectra showed that the amount of the PEO-CP complex formed by hydrogen bonding changed depending on the CP grade. With the cross-linked CP, a good correlation was observed between the hydrogen bonding percent and the percent released of the PHE after 60 min (D(60 min)), indicating that PHE release was controlled by the amount of PEO-CP complex formation in the solid dispersion. These results show that it is feasible to control the medicine release from PEO-CP solid dispersion by varying the CP grade.

Role of CYP1A2 in the toxicity of long-term phenacetin feeding in mice

The mechanisms underlying phenacetin-induced toxicity and carcinogenicity are not clear. In particular, it is not known whether these effects are mediated by metabolic activation of the drug. CYP1A2 is known to metabolize phenacetin in vitro. To determine the role of this enzyme in vivo, the toxicity and carcinogenicity of phenacetin was examined in Cyp1a2-null mice (that lack CYP1A2). Six- to 8-week-old wild type (+/+) or null (-/-) mice were fed either a control diet, or one containing 1.25% phenacetin, ad libitum for up to 67 weeks. Representative groups of mice were examined for phenacetin-induced toxicity and carcinogenicity after 36, 48, 58, or 67 weeks of feeding. Consistent with the known role of CYP1A2 in phenacetin metabolism, plasma levels of phenacetin were higher and acetaminophen levels lower in the (-/-) mice fed phenacetin compared to phenacetin-fed (+/+) controls. Weight gain was significantly depressed in both groups of phenacetin-fed mice after 4 weeks of feeding, and continued to be lower for the remainder of the experiment, compared to controls. Hepatomegaly and splenomegaly were more severe in (-/-) mice but present in both genotypes fed phenacetin at all time points assessed. Histological analysis of liver, kidney, spleen, and urogenital tract also revealed a differential response in the (-/-) mice fed phenacetin compared to (+/+) mice fed the same diet. Further, mortality was the most severe in the (-/-) mice fed phenacetin than in all other groups. Despite significant toxicity in (-/-) mice fed phenacetin, only one renal carcinoma was found among them. Results from this work demonstrate that, in the absence of CYP1A2, phenacetin is more toxic than in controls. This provides evidence that metabolism of phenacetin by CYP1A2 alters toxicity in vivo, and suggests that alternate CYP1A2-independent metabolic pathways contribute to its toxicity.

Analgesic nephropathy in rodents

While it is clear that humans suffer from "classic" analgesic nephropathy, the causative agents and mechanisms are still not known. A review of the literature revealed that chronic acetaminophen exposure does not produce renal papillary necrosis in rodents or humans. In contrast, while chronic aspirin exposure to rodents results in renal papillary necrosis with renal morphological and functional changes similar to that described in humans, epidemiological studies do not implicate aspirin alone in human analgesic nephropathy. The difference in the effects of aspirin in humans and rats may be due to the inability of epidemiological studies to detect aspirin-induced analgesic nephropathy or more likely to the fact that species differences exist, with the rat being more sensitive than humans. With respect to combinations of aspirin and acetaminophen, with or without caffeine, there are minimal tightly controlled studies. In addition, there is little evidence of enhanced renal papillary necrosis in rodents treated with aspirin and acetaminophen combinations. In summary, it remains to be determined what chemical entities cause "classic" analgesic nephropathy in humans and the mechanisms of this toxicity such that preventative measures can be instituted. Elucidation of the mechanisms of analgesic nephropathy has been hampered due to the lack of animal models that closely mimic the human disease. Rodents do not appear to be an appropriate model.

Studies on internal structure of tablets. VI. stress dispersion in tablets by excipients

The aim of this study was to reduce the stress concentration of a medicine by dispersing the stress in tablets at tableting by addition of excipients. The mechanism of the stress dispersion was elucidated. Phenacetin (PHE) was used as a model of crystalline medicine with a high brittleness, and the degree of stress dispersion was evaluated by the change in the exposed surface area of PHE. To learn the mechanical strength of tablets, the crushing strength and friability were measured, their internal structure was analyzed by the porosity and pore size distribution, and stress relaxation experiments were performed. The results were as follows. Calcium silicate (Florite RE, FLR) showed a high stress dispersion effect, adding a high formability and mechanical strength to tablets. It was thought that the high stress dispersion resulted from the rapid stress relaxation caused by the plastic deformation and brittleness fracture of pores in FLR under a low compression pressure. Thus the stress caused locally on PHE particles may disperse.

[The use of cassava starch in the formulation of gelatin capsules]

Cassava, corn and potato starch were, after storage at various conditions of temperature and relative humidity, mixed with a model drug phenacetin. The powder mixtures were filled into hard gelatin capsules. The powder beds containing 20% and 50% starch do not disintegrate within 2 hours. The shortest disintegration time was observed for the mixture containing 80% potato starch. The dissolution rate of phenacetin depends on the porosity of the powder bed filled and the kind of starch used. Potato starch improves the availability of the drug. The disintegration action of corn and cassava starch are almost identical.

[The formulation aspects of drug liberation]

Author raised problems and showed through research data some simple possibilities to achieve controlled release drug liberation. The dosage form developed during drug formulation work may influence the biological effects exerted by the active ingredients and therefore may alter the therapeutic efficacy, too. The dosage from itself includes all the chemical properties of active ingredients (salt-, ester form, polar-apolar material etc.), the physical state (crystal, amorphous, polymorphous, particle size, surface area, solvated state etc.), the value of stability and the parameters of auxiliary materials and manufacturing processes. The aim of formulation -among others-is to achieve the optimal liberation and bioavailability of drugs. The article reviews the possibilities through examples (theophylline, nitrofurantoin, phenacetin, antacids) how to make production prescriptions with high reproducibility used for the preparation of prolonged action systems with controlled release drug liberation.

Different roles for phenacetin and paracetamol in cancer of the kidney and renal pelvis

A population-based case-control study of kidney cancer was carried out in New South Wales using data from structured interviews with 489 cases of renal-cell cancer and 147 cases of renal pelvic cancer diagnosed in 1989 and 1990, together with 523 controls from the electoral rolls. This study showed that the risk of renal pelvic cancer was increased by phenacetin/aspirin compound analgesics (RR = 12.2; 95% CI 6.8-22.2) to a far greater extent than by paracetamol (RR = 1.3; 95% CI 0.7-2.4; not significant). There was a doubling of risk (RR = 2.0; 95% CI 0.9-4.4) in the highest tertile of paracetamol taken in any form compared with values for non-users of any type of analgesic. By contrast, the risk of renal-cell cancer appeared to be increased to a similar degree by phenacetin/aspirin compound analgesics (RR = 1.4; 95% CI 0.9-2.3) and paracetamol taken in any form (RR = 1.5; 95% CI 1.0-2.3). When both drugs were treated as alternative forms of the same risk factor, the risk was increased by 1.7 (95% CI 1.2-2.4). On this evidence, we postulate that phenacetin/aspirin compounds are weakly carcinogenic in the renal parenchyma through the metabolic conversion of phenacetin to paracetamol, and potently carcinogenic in the renal pelvis by different or additional pathways involving renal papillary necrosis. In addition, there is an indication of a weak link between paracetamol and renal pelvic cancer.

Organic dissociative syndrome associated with antimigraine pharmacotherapy

This report describes an acute organic brain syndrome with a fugue-like state in association with antimigraine pharmacotherapy. The differential diagnosis of: 1. possible psychotoxic effects of the combination of propranolol, imipramine, and butalbital; 2. confusional migraine with amnesia; and 3. psychogenic dissociation is considered. Although organically induced dissociative states are of clinical, neuropsychological and medico-legal significance, the DSM-III and DSM-III-R have specific categories only for dissociative conditions that are strictly psychogenic in origin.

Effects of multiple dosing of phenacetin in the micronucleus test

As a part of the international cooperative study to identify the most sensitive regimen in the micronucleus test, phenacetin was given i.p. to male CD-1 mice at doses of 37.5, 75, 150, 300, 400, and 600 mg/kg once, twice, thrice or four times and the bone marrow cells were harvested 24 h after the final dosing. Positive responses were seen at 600 mg/kg after single and triple dosing and at 400 and 600 mg/kg after double dosing. No dose level gave a positive response after quadruple dosing. A repeated-dosing effect was detected at double and triple dosing. Although triple dosing gave the highest magnitude of micronuclei at 600 mg/kg, double dosing showed a sufficient sensitivity and was more convenient from the viewpoint of selecting a suitable test dose and carrying out the micronucleus test.

Micronucleus induction in mouse bone marrow by phenacetin administered intraperitoneally or orally

The extent and time course of induction of micronucleated polychromatic erythrocytes (MNPCEs) in mouse bone marrow were examined after administration of phenacetin as an insoluble suspension in olive oil by intraperitoneal injection (i.p.) or gastric intubation (p.o.) to 2 strains of mice, MS/Ae and CD-1, at doses up to 1200 mg/kg. The toxicity of phenacetin and the sensitivity of micronucleus induction differed in the 2 strains, but there was little difference in the extent of MNPCEs induced by the 2 administration routes.

Early cell proliferative and cytotoxic effects of phenacetin on rat nasal mucosa

The oral analgesic drug phenacetin is known to cause nasal and renal tumors in rats when fed in the diet for 2 years at 1.25 or 2.5%. Long-term exposure to chemicals at cytotoxic concentrations may lead to tumor formation secondary to chronic restorative cell proliferation. In the present experiments, cell proliferative and cytotoxic effects on the nasal mucosa were examined after short-term phenacetin administration. One week of daily gavage treatment of rats with phenacetin at doses comparable to those used in oncogenicity studies resulted in dose-related increases in DNA synthesis in both respiratory and olfactory mucosa. The increase in respiratory mucosa was due to inflammatory cells in the lamina propria and not proliferation of the respiratory epithelial cells. This observation demonstrates a potentially serious artifact in analytical approaches to DNA synthesis using tissue homogenates. One or two weeks of daily phenacetin treatment resulted in degenerative changes in the olfactory epithelium and necrosis of Bowman's glands. These changes were associated with increases in cell proliferation only in the olfactory epithelium. Two-week daily gavage treatment of rats with phenacetin at 100, 625, or 1250 mg/kg/day increased olfactory epithelial cell replication 62.4, 174, or 763%, respectively. The dose-response relationship for cell proliferation was similar to that of nasal tumor formation. These data suggest that the primary site of phenacetin toxicity within the nose is the olfactory mucosa, with restorative cell proliferation being confined to the epithelial cell layer. The data indicated that early cell proliferative responses may be important in the genesis of nasal tumors and that cell proliferation data may be useful for setting dose levels for oncogenicity studies.

Combined hepatic arterial-portal venous and hepatic arterial-hepatic venous perfusions to probe the abundance of drug metabolizing activities: perihepatic venous O-deethylation activity for phenacetin and periportal sulfation activity for acetaminophen in the once-through rat liver preparation

Although normal-retrograde liver perfusion allows definition of relative distribution patterns of multienzyme systems involved in parallel, competing and sequential metabolic pathways, the technique fails to describe localization patterns for unienzyme systems. A novel method of perfusion, which can describe the relative zonal enrichment of drug metabolizing activity of unienzyme systems in periportal region and in the entire liver, is described. The rat liver was perfused once-through with combined hepatic arterial (2 ml/min/liver-containing drug) and portal or hepatic venous (10 ml/min/liver, without drug) flows [HAPV and HAHV]. Because of known enrichment of phenacetin O-deethylation and acetaminophen sulfation activities in the perihepatic venous and periportal regions, respectively, metabolic data derived with these compounds were used for validation of the method. The overall steady-state hepatic extraction ratio of [3H]phenacetin during HAPV (0.88-0.98) was decreased markedly during HAHV (0.06-0.47), but was reduced to a lesser extent for preformed [3H]acetaminophen (0.57-0.86 for HAPV to 0.23-0.62 for HAHV). Because a comparison of metabolic activities encountered by substrate(s) [estimated from extraction ratios] required normalization to the intracellular water spaces accessed during both HAPV and HAHV, the multiple indicator dilution technique (a bolus injection of noneliminated reference materials: 51Cr-labeled RBC, 125I-labeled albumin, [14C]sucrose and 3H2O) into the hepatic artery during both HAPV and HAHV was used, with outflow profiles from the hepatic vein or portal vein characterized by rapid serial collections. Sinusoidal blood volume, albumin accessible Disse space, sucrose accessible Disse space and the estimated intracellular water space reached during HAHV were 48, 56, 53 and 33% those during HAPV. The ratios of intrinsic clearances per volume of cell water space for HAHV/HAPV, representing periportal activity/whole liver activity were: phenacetin O-deethylation, 0.34 and acetaminophen sulfation, 1.13. These findings validate the use of HAHV and HAPV perfusion for the examination of relative abundances of enzymic activities across the liver acinus for substrates metabolized by unienzyme systems.

Heavy phenacetin use and bladder cancer in women aged 20 to 49 years

We investigated the use of analgesics containing phenacetin or acetaminophen in 173 young women with urinary bladder cancer and 173 matched controls. The cases, who were 20 to 49 years old at the time of diagnosis of cancer, were 6.5 times more likely to report regular use of analgesics containing phenacetin at least one year before diagnosis than were their matched controls (odds ratio, 6.5; 95 per cent confidence interval, 1.5 to 59.2). Among the 15 women (13 cases and 2 controls) reporting regular use of phenacetin-containing drugs, 8 of the cases and 1 of the controls reported daily use for over one year (P = 0.04). Excessive use of analgesics containing acetaminophen was not reported. The increased risk of bladder cancer in young women who regularly used phenacetin-containing products remained present after adjustments for all other identified risk factors.

Ultrasonic findings in analgesic nephropathy

34 patients with analgesic nephropathy (AN) were investigated by real-time ultrasonography. In 11 out of 14 patients on maintenance dialysis and in 16 out of 20 patients with renal insufficiency calcified renal papillae were documented surrounding the central sinus in a typical garland pattern. Moreover, by surveying a group of patients with renal insufficiency of unknown origin, AN was assumed in 10 patients and was then confirmed by a hitherto unknown history of analgesic abuse as well as by laboratory findings. In 37 patients radiologic or autopsy data were additionally available. A close correlation to the scanning pattern was found in 31 of these patients. In 30 healthy volunteers and 56 patients with renal insufficiency due to chronic glomerulonephritis (n = 24) or diabetic nephropathy (n = 32) calcified renal papillae were found only in 1 case. 5 out of 20 patients on maintenance dialysis due to other diseases than AN showed renal calcifications forming an approximate garland arrangement. In these patients sonography may therefore indicate AN only in very characteristic cases. We believe that renal papillary calcifications surrounding the central sinus in a garland pattern may indicate AN in most cases and thus may be helpful in establishing the diagnosis of AN.

Combination analgesics

Six rationales for using combination analgesics are identified, but most combinations are formulated with two rationales in mind: enhancement of analgesia and reduction of adverse effects by combining two analgesics with different mechanisms of action. Acetaminophen and aspirin are the mainstays of oral analgesic combinations. There is substantial evidence that combining an optimal dose of acetaminophen or aspirin with an oral opioid such as codeine, hydrocodone, or oxycodone produces an additive analgesic effect greater than that obtained by doubling the dose of either constituent administered alone. There is also some evidence that the adverse effects produced by such combinations are less than would be produced by an equi-analgesic dose of a single constituent. The physician need not be confined to existing fixed-ratio combinations; he or she may extemporize to the patient's advantage by co-administering acetaminophen, aspirin, or other nonsteroidal anti-inflammatory drugs with available oral opioids and, in select situations, co-administering oral or injectable analgesics with psychoactive drugs.

In vitro drug release from egg albumin microcapsules

The in vitro release of phenacetin from microcapsules prepared using egg albumin as the membrane material was investigated. It was shown by scanning electron microscopy that the albumin microcapsules have nonsmooth surfaces. The amount of phenacetin released is proportional to the square root of time up to 50-70% drug release. Increases in the albumin concentration and 1-vinyl-2-pyrrolidinone polymer content in the aqueous phases used in the microcapsule preparation have an effect on matrix porosity and channel tortuosity in the matrix of albumin microcapsules. The in vitro release rate was found to decrease with increasing albumin concentration and 1-vinyl-2-pyrrolidinone polymer content in the aqueous phases. The in vitro release rate per unit area also decreased with decreasing capsule size.

The combined effect of mechanical trauma and phenacetin or sodium saccharin on the rat urinary bladder

The effect of 0.535% phenacetin or 5% sodium saccharin administered in the diet on proliferating urothelium in 160 Sprague-Dawley rats was studied by light microscopy and scanning electron microscopy. Reparative urothelial proliferation was induced by perforating the urinary bladder with a 23 gauge needle. The rats were then treated with phenacetin or sodium saccharin for up to 70 weeks. Non-perforated rats treated with phenacetin or sodium saccharin developed a slowly increasing urothelial hyperplasia detectable by light microscopy and SEM examination. When the rats were subjected to perforation of the bladder followed by phenacetin or sodium saccharin there was a significant increase in the incidence and severity of the hyperplastic lesions compared to rats treated with phenacetin or sodium saccharin alone. Although pleomorphic microvilli were detected on the luminal surface of the bladder in 30 of 160 rats, only 2 rats developed bladder tumors. Among female rats pleomorphic microvilli, although initially frequently present, seemed to disappear. The presence of pleomorphic microvilli therefore seems also to be consistent with a reversible hyperplasia.

The influence of phenacetin or mechanical perforation on the development of renal pelvic and urinary bladder tumors in FANFT-induced urinary tract carcinogenesis

The influence of 0.535% phenacetin in the diet or mechanical perforation of the renal pelvis and urinary bladder of male Sprague-Dawley rats in FANFT-induced urinary tract carcinogenesis was studied. The 151 rats were divided into 5 experimental and one control group. The rats were followed for up to 80 weeks. FANFT administered at 0.2% in the diet for 11 weeks resulted in a high incidence of urinary tract tumors particularly of the renal pelvis. Similar results were obtained by administration of 0.2% FANFT for 6 weeks followed by 0.535% phenacetin while FANFT for 6 weeks preceded or followed by mechanical perforation of the renal pelvis resulted in a significantly lower incidence of renal pelvic tumors. Phenacetin appeared to enhance the development of renal pelvic tumors in FANFT-induced urinary tract carcinogenesis. In contrast no effect of phenacetin on the urinary bladder could be detected.

Rotary press utilizing a flexible die wall

A die with a flexible wall was constructed and evaluated on a specially modified instrumented rotary tablet press. The design permits an inward deflection of the die wall by a side punch, which rolls past a side compression roll during compression-decompression. The side compression roll is instrumented to monitor the applied side compression roll forces. On decompression, return of the die wall to its original position permits release of residual die wall pressure. The decreased residual die wall pressure can decrease fracture and capping of tablets for problem formulations. The performance was tested on three experimental formulations. For these formulations, tablets made in a conventional die exhibited severe capping problems. However, most tablets compressed in the special die were superior. With proper adjustment of punch and die wall compression forces, excellent tablets could be manufactured. The merits of the special die and modified tablet machine are substantiated, although this initial design did not provide adequate die wall pressure for all formulations. Further engineering efforts could result in practical production equipment.

Preparation of microcapsules using the n-butyl half-ester of PVM/MA coacervate system

The n-butyl half-ester of the polymer polyvinyl methyl ether maleic anhydride was used for the preparation of microcapsules applying a simple encapsulation process which is less difficult to control than other methods of phase separation encapsulation. The data demonstrated that the release of the drug from the microcapsules can be controlled by changing the ratio of the amount of the drug to shell substance.

Preparation of egg albumin microcapsules and microspheres

Protein microspheres and microcapsules containing fine hydrophilic particles (spherical silica gel beads, iron hydrous oxidemodified nylon 12, or phenacetin) were prepared by using water-soluble egg albumin, which is heat-coagulable at 50-80 degrees. The size and size distribution of the microspheres and microcapsules formed and the microencapsulation percentage of fine particles were determined, and the factors affecting them were studied. Favorable conditions are suggested to obtain phenacetin-containing microcapsules in high yield.

Intraindividual variation in drug disposition

Large interindividual differences occur in the in vivo metabolism of drugs due to genetic and environmental factors. Our studies show that intraindividual variabilities in rates of metabolism are relatively low for antipyrine and phenylbutazone, which are drugs that are primarily metabolized by the liver and have low hepatic extractions; whereas in the case of phenacetin, a drug that undergoes extensive metabolism in the gastrointestinal tract or during its first pass through the liver, or both, intraindividual variations in plasma half-lifes and areas under the plasma concentration-time curves are of much greater magnitude. In our studies, no effort was made to control the lifestyles of our subjects. The variations in rates of drug metabolism did not result from assay procedures, since there was little variation in measured concentrations when the drugs were added to plasma and assayed on multiple occasions. Intraindividual variation occurring in subjects given the drug on 5 different occasions may be due to changes in the external environment or changes in internal physiologic parameters or both. Our studies confirm the usefulness of antipyrine as a test drug in studying drug metabolism in man and also demonstrate that the antipyrine test may be able to detect those subjects whose environments are perturbed by unidentified factors.

[Kidney lesion from phenacetin]

After a short survey of the most important toxical lesions of the human organism by phenacetin a report is given on a 65-year-old female patient. An abuse of phenacetin lasting 20 years (calculated total quantity: more than 1 kg) led to a lesion of the kidney and rejection of the papilla. The anamnesis confirms the frequently thoughtless prescription of phenacetin-containing medicaments and emphasizes their sequelae. By a clarifying talk with the appreciative patient the abuse of phenacetin could be finished.