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Biomedical subjects

A Naik

Publications and source records attributed to A Naik.

30 records · Page 2Linked to original sources
PubMed2000

Transdermal drug delivery: overcoming the skin's barrier function.

The skin represents an extraordinary evolutionary feat. Not only does it physically encapsulate the organism and provide a multifunctional interface between us and our surroundings, but it is perpetually engaged in the assembly of a highly efficient homeostatic barrier to the outward loss of water(1). In so doing, it furnishes a membrane that is equally adept at limiting molecular transport both from and into the body. Overcoming this barrier function then, for the purpose of transdermal drug delivery, has been a necessarily challenging task for the pharmaceutical scientist, and one that boasts significant progress.

Journal Article↗
PubMed2000

Transdermal macromolecular delivery: real-time visualization of iontophoretic and chemically enhanced transport using two-photon excitation microscopy.

PURPOSE: To investigate the transdermal delivery of a model macromolecule by passive and iontophoretic means following pretreatment with C12-penetration enhancers and to visualise transport across human stratum corneum (SC) in real time. METHODS: Transport studies of dextran, labelled with fluorescent Cascade Blue (D-CB: M(R) = 3 kDa) across human stratum corneum, were conducted during passive and iontophoretic modes of delivery following pretreatment with either dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulphate (SDS) or Azone. Size-exclusion chromatography was used to assess maintenance of dextran structural integrity throughout experimental lifetime. Two-photon excitation microscopy was employed to visualise real-time dextran transport during current application. RESULTS: The positively charged C12-enhancer DTAB elevated passive D-CB steady-state flux (J(ss)) and was the only enhancer to do so above control during iontophoresis. The negatively charged SDS had the least effect during both stages. On-line macromolecular transport was visualised, indicating both inter- and intra-cellular pathways across SC during current application. No transport was visible across untreated SC during passive transport. CONCLUSIONS: Use of a positively charged enhancer may improve J(ss) of anionic macromolecular penetrants during passive and iontophoretic delivery. On-line visualisation of iontophoresis across SC was possible and can provide mechanistic insight into SC transport pathways.

Administration, Cutaneous↗
PubMed1999

Comparison of efficacy of intravenous diltiazem and esmolol in terminating supraventricular tachycardia.

OBJECTIVE: Paroxysmal supraventricular tachycardia (PSVT) can be effectively terminated by the intravenous administration of adenosine or verapamil. However adenosine is expensive and injectable verapamil currently is scarcely available. While intravenous diltiazem has been shown to be useful for terminating PSVT, the efficacy of esmolol in this regard has not been evaluated previously. Hence these latter two drugs were studied for their efficacy in terminating PSVT. METHODS: A prospective, randomised, crossover study was undertaken in patients presenting with hemodynamically tolerated PSVT to the ICCU. While 50 patients had been planned for the trial, the study had to be prematurely terminated after 32 patients had been enrolled due to the marked superiority of diltiazem. Two sequential doses with a 5 minute interval of either drug were administered before crossover. Diltiazem was given in a dose of 0.25 mg/kg while the esmolol dose was 0.5 mg/kg. RESULTS: Diltiazem terminated PSVT in all the 16 patients in whom it was given as the first drug. The 12 patients who did not respond to esmolol were also effectively treated with diltiazem. Thus totally 28/28 patients responded to diltiazem while only 4/16 patients responded to esmolol (p < 0.001). Of the 28 patients who responded to diltiazem, in 13 patients the second bolus of diltiazem worked after the first one had failed. No significant adverse effects were seen. CONCLUSION: Intravenous diltiazem is highly effective and safe for terminating PSVT. When the first bolus is ineffective, the second bolus given after 5 minutes usually succeeds. Esmolol in the dose of 0.5 mg/kg has poor efficacy for terminating PSVT, even when 2 boluses are administered.

Adrenergic beta-Antagonists↗
PubMed1998

Transcatheter closure of patent ductus arteriosus in children weighing < 10 kg with Gianturco coils using the balloon occlusion technique.

We evaluated the immediate and intermediate follow-up results of transcatheter closure (TCC) of patent ductus arteriosus (PDA) using Gianturco coils in children weighing < 10 kg. The results of PDA < or = 2.5 mm (group I, n = 18) and > 2.5 mm (group II, n = 16) were compared. Coils were deployed sequentially by transarterial route using a temporary balloon occlusion technique. The immediate clinical success rate in both groups was comparable. There was no significant difference in the number of coils required per patient and in the embolization rate between the two groups. Both groups had comparable occlusion rates at intermediate-term follow-up. At intermediate follow-up, one patient had developed left pulmonary artery stenosis while obstruction of the descending aorta was not seen in any; in 4 children the PDA had recanalized. Spontaneous reocclusion was observed in 3 of the latter at the last follow-up. We conclude that TCC of PDA is feasible and safe in children weighing < 10 kg with gratifying intermediate-term results.

Aortography↗
PubMed1993

Validation of reflectance infrared spectroscopy as a quantitative method to measure percutaneous absorption in vivo.

Attenuated total-reflectance infrared (ATR-IR) spectroscopy has been used to follow the penetration of a model compound (4-cyanophenol; CP) across human stratum corneum (SC) in vivo, in man. CP was administered for periods of 1, 2, or 3 hr, either (a) as a 10% (w/v) solution in propylene glycol or (b) in an identical vehicle which also contained 5% (v/v) oleic (cis-9-octadecenoic) acid. At the end of the treatment periods, SC at the application site was progressively removed by adhesive tape-stripping. Prior to the removal of the first tape-strip, and after each subsequent tape-strip, an ATR-IR spectrum of the treated site was recorded. The presence of CP, as a function of position in the SC, was monitored spectroscopically via the intense C = N stretching absorbance at 2230 cm-1. The absolute amount of CP, as a function of SC depth, was determined by "spiking" the applied solutions with 14C-labeled compound and subsequent liquid scintillation counting of the removed tape-strips. The presence of oleic acid in the applied formulation significantly increased the rate and extent of CP delivery as evaluated by either spectroscopy or radiochemical analysis. Furthermore, the ATR-IR and direct 14C analysis of CP as a function of SC position were highly correlated. These data strongly support, therefore, the validation of ATR-IR as a quantitative tool to assess percutaneous penetration in vivo.

Administration, Cutaneous↗
PubMedDate not supplied

Colloid carcinoma of rectum in a 11 year old child.

The rarity of rectal carcinoma in children has prompted us to report this patient who presented with bleeding per rectum and constipation. Histopathological examination of biopsy revealed the growth to be a colloid carcinoma of rectum and it was inoperable on exploratory laparotomy. There are three factors which contribute to an overall poor prognosis of rectal carcinoma in children viz. delay in diagnosis, advanced stage of disease and poorly differentiated histology.

Adenocarcinoma, Mucinous↗