A validated chiral LC method for the enantioselective analysis of Levetiracetam and its enantiomer R-α-ethyl-2-oxo-pyrrolidine acetamide on amylose-based stationary phase

A new, simple chiral HPLC method was developed for the enantiomeric separation of Levetiracetam, [(S)-alpha-ethyl-2-oxo-pyrrolidine acetamide], an antiepileptic drug in pharmaceutical formulations and in bulk materials. Enantiomeric separation was achieved on a chiralpak AD-H column using a mobile phase consisting of hexane and isopropanol in the ratio (90:10, v/v) at a flow rate of 1.0 ml/min. The resolution between the enantiomers was found to be not less than 7 in the optimized method. Interestingly, unwanted enantiomer, namely R-alpha-ethyl-2-oxo-pyrrolidine acetamide ((R)-enantiomer), was eluted prior to its mirror image in the developed method. The developed method was found to be selective in the presence of related impurities of Levetiracetam, namely N-(1-carbamoyl-propyl)-4-chloro-butyramide (Imp-1) and 1-ethyl-2-oxo-1-pyrrolidine acetic acid (Imp-2), and also under exposed conditions of UV light and 60 degrees C. The limit of detection (LOD) and limit of quantification (LOQ) of (R)-enantiomer were found to be 900 and 2250 ng/ml, respectively, for 10 microl injection volume. The method precision for (R)-enantiomer at limit of quantification level was within 8% R.S.D. Calibration curve for (R)-enantiomer was linear over the studied ranges (2250-9000 ng) with correlation coefficient greater than 0998. The active pharmaceutical ingredient was extracted from its finished dosage form (tablet) using isopropanol. The percentage recoveries of (R)-enantiomer were ranged from 94.2 to 102.6 and from 93.5 to 104.1 in spiked bulk and formulation samples of Levetiracetam, respectively. Levetiracetam sample solution and mobile phase are found to be stable for at least 48 h. The developed method was found to be rugged and robust. The proposed method was found to be suitable and accurate for the quantitative determination of (R)-enantiomer in bulk drugs and commercial formulations. Chiralcel OD-H column can also be used as an alternative column for the above purpose.

Effective atomic numbers of biological materials in the energy region 1 to 50 MeV for photons, electrons, and He ions

A study of effective atomic numbers for biological materials such as bone, muscle, spleen, liver, mucin, and water has been carried out in the energy region 1 to 50 MeV for photons, electrons, and He ions. It is noticed that the effective atomic number for photons and electrons increases with energy, and remains, more or less the same, for He ions.

Investigation on the reduction of electron contamination with a 6-MV x-ray beam

Experimental investigations have been carried out on the reduction of electron contamination of a 6-MV x-ray beam of Clinac model 1800 for square field sizes 5 X 5 to 30 X 30 cm2 in steps of 5 cm and for rectangular field sizes 19 X 7 and 7 X 19 cm2. The electron contamination of both the open beam and the beam with the tray can be effectively reduced by placing a lead foil filter immediately below the blocking tray. Measurements at 100-cm source-skin distance with filter in place showed a reduction in dose in the buildup region and also a displacement of the location of Dmax to greater depths, even for small field sizes such as 10 X 10 cm2.

Investigations on the near surface dose for three 10-MV x-ray beam accelerators with emphasis on the reduction of electron contamination

A study of three 10-MV x-ray clinical accelerators with emphasis on the reduction of electron contamination was conducted. This study, which was performed with different types of trays and filters, suggests that, at 100-cm source-surface distance (SSD), Pb can be used as an effective filter material up to 30 X 30 cm2; however, due to its transparency, a Clear-Pb tray is useful for field sizes up to a 20 X 20 cm2. Percent depth doses for a few selected depths and field sizes at this nominal SSD were examined. No significant differences, with the exception of the location of Dmax, amongst the three accelerators were noticed.

Interaction of low-energy photons with biological materials and the effective atomic number

The effective atomic numbers for total photon interaction in bone, muscle, liver, spleen, fat, and water are determined and found to decrease up to 50% as the energy increases from 10 to 200 keV. Muscle, spleen, liver, and water are found to behave in an approximately similar manner in this energy region, as far as photon interaction is concerned.

Depression in general practice: clinical features and comparison with out-patients

General practice (GP) depressives prescribed an antidepressant were compared with those given other treatment, and with antidepressant-treated psychiatric out-patient depressives. GP depressives were considerably less severely ill than out-patients, with fewer depressive symptoms and shorter illness, as well as less primary and less endogenous depression. The two groups of GP depressives differed less, but those receiving other treatment tended to have less severe depression than those receiving antidepressants and were less likely to satisfy diagnostic criteria for depression. Depressives in GP differ considerably in clinical characteristics from psychiatric out-patient depressives, and clinical features influence the GP's decision to treat with antidepressants.

Depression in general practice: case thresholds and diagnosis

Using multiple diagnostic and epidemiological criteria, three samples of general practice (GP) depressives were studied: those prescribed a new course of antidepressants, those given other treatment, and those missed by the GP. The majority of patients qualified as psychiatric cases on the PSE Index of Definition, the Bedford College Criteria, and the Research Diagnostic Criteria. Most satisfied diagnostic criteria for depression, or (fewer) anxiety. The disorders were relatively mild and often borderline on all three systems. Depressives given other treatment most often failed to meet diagnostic criteria. About half the antidepressant treated patients received RDC diagnoses of major depression. Among the other treatment sample, only one-fifth met these criteria, and half had non-depressive diagnoses. Most cases of depression treated by GPs satisfy criteria for psychiatric disorder, but tend to be relatively mild and borderline in quality.

Unrecognised depression in general practice

Patients attending their general practitioner were screened and a group with unrecognised major depressive disorder identified. This group was interviewed and the findings compared with those in a group of patients recognised correctly as depressed by their general practitioners. Half of the patients with severe depression screened in their doctors' waiting rooms went unrecognised, and they differed in few ways from those who were recognised. The differences found were that the patients with unrecognised depression were less obviously depressed and their illness had lasted longer. Physical illness was present in nearly 30% of patients in the unrecognised group, and the depression seemed related to it. Patients with unrecognised depression were more likely to have feelings other than those of normal sadness and more likely to respond with change of mood to intercurrent events. These data suggest that patients might benefit if general practitioners were better trained to recognise depression, although it is not known whether treatment would be effective.

Life stress and symptom pattern in out-patient depression

The relationship was examined between symptoms rated in a sample of out-patient depressives, and measures of life stress derived from a separate interview. There was an association between symptoms reflecting the endogenous-neurotic distinction and life stress. However, the association was relatively weak, and was mainly with total social problems at the time of presentation, rather than with life events at onset. These findings are consistent with other studies which indicate that the absence of prior life events and the presence of the endogenous symptom pattern are only weakly related.

Nosology of atypical depression

A review of the literature on atypical depression indicated three relatively separate usages for the term: anxiety or phobic symptoms additional to depression, reversed functional shift, and non-endogenous depression. A sample of 160 out-patient depressives was rated on a variety of diagnostic systems measuring these concepts. Inter-relationships between groups selected by the three definitions were found to be low. In addition, although there was moderate consistency within different definitions of endogenous depression and of additional anxiety, reversed functional shift symptoms did not correlate well with each other. These findings suggest that atypical depression may be of limited value as a specific diagnosis within non-psychotic depression.