Stability studies of ionised and non-ionised 3,4-diaminopyridine: hypothesis of degradation pathways and chemical structure of degradation products.

3,4-Diaminopyridine is used to treat some symptoms met in Lambert-Eaton myasthenia syndrome. It was shown efficient to reduce a form of variable muscle weakness and fatigability typical of the disease and correlated to a block of acetylcholine release. In France, 3,4-diaminopyridine is nowadays given to patients under capsules form and the status of hospital preparation. Whatever the diluant used in the formulation, the stability period could not exceed 12 months. Preliminary studies were made on a salt form in order to test the influence of various stress factors and determine if there is interaction between them. From this study, the most influent stress condition, presence of hydrogen peroxide, was selected and a comparative study was performed to compare the stability of molecular and salt species. Solutions of each species were exposed to 5 or 15% of hydrogen peroxide and analyzed at 8, 24, 72 and 216 h of degradation by HPLC-UV. Fractions of detected impurities were purified and collected by semi-preparative HPLC-UV and analyzed by HPLC-UV-ESI-MS and IR spectroscopy in order to determine their structure hypotheses. Theses experiments demonstrate that the salt species were more stable under oxidative stress condition than molecular species. The two main degradation products were collected and identified as 4-amino, 3-nitropyridine and 3,4-diaminopyridine-N-oxide when the molecular form was degraded whereas only 4-amino, 3-nitropyridine was found in less quantity in the salt solutions. Nitrogen pyridine and pyridine amine could not easily be oxidized by hydrogen peroxide in salt comparatively to molecular species due to the lone pair of electron engaged in a bound with hydrogen in the first case and by resonance change of the pyridine in the second case. This modification of structure promoted different pathways of degradation for the salt form which are more dependent of energy. Owing to the better stability of the salt species, a new pharmaceutical form containing it was developed to assess its stability under ICH standard conditions allowing an industrial manufacture of this drug.

Determination of A 3,4-diaminopyridine in plasma by liquid chromatography with electrochemical detection using solid-phase extraction.

In order to quantify a small amount of a drug, 3,4-diaminopyridine (3,4-DAP), in animal plasma samples, an analytical method was developed. It involved an extraction of 3,4-DAP and phenylephrine, used as internal standard (IS), from plasma with solid-phase extraction (SPE) on C18 cartridges. This analytical method is a hyphenated technique based on high-performance liquid chromatography with electrochemical detection (HPLC-EC) whose purpose is to obtain first a sensitive method and second a satisfying separation between 3,4-DAP and phenylephrine. The analytical method is accurate, specific, and linear between 10 and 500 g of 3,4-DAP per litre. The recovery of 3,4-DAP is estimated at 70.8% with a 95% confidence interval of (66.0 -75.6%). Intermediate precision was evaluated on three quality control samples; the intra-day precision was estimated at 13.5, 9.1, 7.8% and the inter-day precision at 17.9, 8.4, 9.3%. The limit of quantification of the method was evaluated at 10 g l-1. First toxicokinetic parameters determined on dogs plasma samples after one 3,4-DAP oral administration of 1 mg kg-1 were: Cmax=395.7 microg l-1; Tmax =15 min; t1/2=113.6 min; Clearance/F=16.8 ml kg-1 min-1 and Vd/F=2.7 l kg -1.

[Comparative experimental study of the renal consequences of vesico-ureteric reflux and of ureteric obstruction in the sheep foetus (author's transl)]. / Etude expérimentale comparée des conséquences rénales du reflux vésico-urétéral et de l'obstruction urétérale chez le foetus de brebis.

The authors sought to determine what links existed between foetal vesico-ureteric reflux and renal dysplasia. Using sheep with operation upon the foetuses in utero, at a fairly early stage of gestation, the following were obtained: 1) Foetal vesico-ureteric reflux by unilateral excision of a ureteric meatus. 2) Stenosis of the foetal ureter by ligation. In the first case, no renal dysplasia occurred. In the second case, dysplasia-type parenchymatous lesions were found. This led them to conclude that the direct relationship between isolated foetal vesico ureteric reflux created experimentally in a normal ureter (without any additional functional or organic obstructive factor) and renal dysplasia could not be demonstrated in the sheep foetus.

[A critical review of the variations in size of the kidney caused by increased diuresis in hypertensive patients (author's transl)]. / Les variations de taille du rein sous l'effet de l'hyperdiurèse dans l'hypertension artérielle. Etude critique.

The authors studied the validity of Wolf and Dorph's test (increase in size of the kidney with increased diuresis) performed during intravenous urography in hypertensive patients. The technical procedure is described, and the results reported: 1 032 kidneys were measured, of which 84 had been also examined by arteriography. The results are analyzed and compared to those obtained after the standard method of early consecutive films, with the following conclusions: -- the test is not as valid as is suggested by the authors who described it; -- the information supplied by the standard method is more consistent and precise; -- the results of these two series are not completely superimposable; -- that even if Wolf and Dorph's test can sometimes supply useful information, it must not be relied upon completely.

[The radiological exploration of renal tumour syndromes [author's transl)]. / Exploration radiologique des syndromes tumoraux rénaux.

Four radiological examinations are available to the clinician for the diagnosis of renal tumour syndromes: intravenous pyelography with vascular nephrotomography is used to make an initial classification. Hypervascularised masses, usually malignant, remain the indication of choice for renal arteriography. Apparently avascular or doubtful masses should first be studied by ultrasound echotomography which offers the possibility of a second classification into fluid-filled tumours, the cystic nature of which may be confirmed by translumbar puncture followed by kystography, and solid or doubtful tumours, suggestive above all of a necrosed carcinoma. In this latter case, the indications for renal arteriography with the use of angiotensin, translumbar puncture or immediate exploratory lumbotomy must be decided in the light of individual cases and local preferences.

Angiographic study of renal vein involvement in renal cell carcinoma.

High dose selective renal arteriography was performed in 62 cases of renal cell carcinoma to study the patency of the renal vein trunk. Arteriographic findings were correlated with histopathology in all cases. In 35 cases of angiographic patency of the renal vein surgery always confirmed the findings. 11 false positive results were observed (the arteriographic diagnosis of venous involvement was not found at surgery). The authors believe that this method is easy and reliable; inferior cavagraphy is not necessary when arteriography shows the patency of the vein.

[The diagnostic possibilities and limitations of arteriography in necrosed carcinomas of the kidney (author's transl)]. / Les possibilités et les limites diagnostiques de l'artériographie dans les cancers nécrosés du rein.

On the basis of a review of 186 cases of carcinoma of the kidney studied by arteriography in the Department of Radiology for Diseases of the Urinary Tract at Necker Hospital, the authors drew the following conclusions: 1. The diagnosis of carcinoma could be affirmed in the very great majority of cases and suspected in the others. 2. There were no instances of a reassuring false diagnosis (cyst). 3. A precise, rigourous and faultless technique, perfectly demonstrating the exteriorised part of the mass and attentive, thorough and careful interpretation of the films obtained, in particular with regard to the mass in its exteriorised portion, are always essential in order to obtain such results. In particular, the presence of a vascularisation of a discontinuous opaque band at the periphery of the mass in its exteriorised part indicates a strong suspicion of a necrotic malignancy and under no circumstances is an unreserved diagnosis of a cyst possible. 4. Diagnostic errors in the sense of false positives involving certain "thick-walled" cysts should be eliminated by pre-operative needle puncture. 5. The authors conclude by describing the method of radiological exploration which they feel to be desirable in practice following the discovery of a renal mass by intravenous pyelography.

[Radiological diagnosis of tumoral lipomatosis of the renal sinus. The role of arteriography (author's transl)]. / Le diagnostic radiologique de la lipomatose pseudo-tumorale du sinus rénal Place de l'arteriographie.

In twenty cases of pseudo-tumoral sinusal lipomatosis for which the patients had undergone renal arteriography, the authors investigated the urographical and arteriographical clinical signs by comparing them with the previously published data. After reviewing these various elements and considering the various possible diagnoses, they came to the conclusion that, although the arteriographic signs are quite distinctive, they are not absolutely essential for diagnosis of this disorder--which it should be possible to confirm unreservedly from the urographical data in all cases in which there are considerable anatomical lesions. A well-managed urographical technique and careful assessment of the facts should allow arteriography to be discarded, indications for this only being justified where there is an associated symptomatology, especially haematuria.

[Management of renal trauma in the child (author's transl)]. / Conduite à tenir lors d'un traumatisme rénal chez l'enfant

Intravenous pyelography remains the basic examination in the study of the child with lumbar trauma. This examination has its limits, however, and renal arteriography may be necessary in a fair number of cases. Provided that adequate reflection is given and the appropriate moment chosen, it is well tolerated and provides all the necessary information.