Search PubMed⌕ Search

Biomedical subjects

R Jalil

Publications and source records attributed to R Jalil.

At least 19 recordsLinked to original sources
PubMed2001

Failure of high doses of calcitriol and hypercalcaemia to induce apoptosis in hyperplastic parathyroid glands of azotaemic rats.

BACKGROUND: Whether calcitriol administration, which is used to treat secondary hyperparathyroidism in dialysis patients, induces regression of parathyroid-gland hyperplasia remains a subject of interest and debate. If regression of the parathyroid gland were to occur, the presumed mechanism would be apoptosis. However, information on whether high doses of calcitriol can induce apoptosis of parathyroid cells in hyperplastic parathyroid glands is lacking. Consequently, high doses of calcitriol were given to azotaemic rats and the parathyroid glands were evaluated for apoptosis. METHODS: Rats were either sham-operated (two groups) or underwent a two-stage 5/6 nephrectomy (three groups). For the first 4 weeks, all rats were given a high (1.2%) phosphorus (P) diet to stimulate parathyroid gland growth and then were changed to a normal (0.6%) P diet for 2 weeks. At week 7, three of the five groups were given high doses of calcitriol (500 pmol/100 g body weight) intraperitoneally every 24 h during 72 h before sacrifice. The five groups during week 7 were: (i) normal renal function (NRF)+0.6% P diet; (ii) NRF+0.6% P+calcitriol; (iii) renal failure (RF)+0.6% P; (iv) RF+1.2% P+calcitriol; and (v) RF+0.6% P+calcitriol. Parathyroid glands were removed at sacrifice and the TUNEL stain was performed to detect apoptosis. RESULTS: At sacrifice, the respective serum calcium values in calcitriol-treated groups (groups 2, 4, and 5) were 15.52+/-0.26, 13.41+/-0.39 and 15.12+/-0.32 mg/dl. In group 3, PTH was 178+/-42 pg/ml, but in calcitriol-treated groups, PTH values were suppressed, 8+/-1 (group 2), 12+/-2 (group 4), and 7+/-1 pg/ml (group 5). Despite, the severe hypercalcaemia and marked PTH suppression in calcitriol-treated groups, the percentage of apoptotic cells in the parathyroid glands was very low (range 0.08+/-0.04 to 0.25+/-0.20%) and not different among the five groups. CONCLUSIONS: We found no evidence in hyperplastic parathyroid glands that apoptosis could be induced in azotaemic rats by the combination of high doses of calcitriol and severe hypercalcaemia despite the marked reduction in PTH levels that was observed.

Animals↗
PubMed2001

Effect of calcitriol treatment and withdrawal on hyperparathyroidism in haemodialysis patients with hypocalcaemia.

BACKGROUND: Calcitriol is used to treat secondary hyperparathyroidism in dialysis patients. For similarly elevated parathyroid hormone (PTH) levels, the PTH response to calcitriol treatment is believed to be better in hypocalcaemic dialysis patients than in dialysis patients with higher serum calcium values. Furthermore, few studies have evaluated the rapidity of the rebound in serum PTH values after prolonged treatment with calcitriol. Our goal was to evaluate (i) the PTH response to calcitriol treatment in hypocalcaemic haemodialysis patients, (ii) the rapidity of rebound in PTH after calcitriol treatment was stopped, and (iii) whether the effect of calcitriol treatment on PTH levels could be separated from those produced by changes in serum calcium and phosphate values. METHODS: Eight haemodialysis patients (29+/-3 years) with hypocalcaemia and hyperparathyroidism were treated thrice weekly with 2 microg of intravenous calcitriol and were dialysed with a 3.5 mEq/l calcium dialysate. Parathyroid function (PTH-calcium curve) was determined before and after 30 weeks of calcitriol treatment and 15 weeks after calcitriol treatment was stopped. RESULTS: Pretreatment PTH and ionized calcium values were 907+/-127 pg/ml and 3.89+/-0.12 mg/dl (normal, 4.52+/-0.07 mg/dl). During calcitriol treatment, one patient did not respond, but basal (predialysis) PTH values in the other seven patients decreased from 846+/-129 to 72+/-12 pg/ml, P<0.001 and in all seven patients, the decrease exceeded 85%. During the 15 weeks after calcitriol treatment was stopped, a slow rebound in basal PTH values in the seven patients was observed, 72+/-12 to 375+/-44 pg/ml. Covariance analysis was used to evaluate the three tests of parathyroid function (0, 30, and 45 weeks), and showed that calcitriol treatment was associated with reductions in maximal PTH values while reductions in basal PTH were affected by ionized calcium and serum phosphate. The basal/maximal PTH ratio and the set point of calcium were associated with changes in ionized calcium. CONCLUSIONS: In haemodialysis patients with hypocalcaemia, (i) moderate to severe hyperparathyroidism responded well to treatment with calcitriol, (ii) reductions in maximal PTH were calcitriol dependent while reductions in basal PTH were affected by the ionized calcium and serum phosphate concentrations, (iii) changes in the basal/maximal PTH ratio and the set point of calcium were calcium dependent, and (iv) the delayed rebound in basal PTH levels after withdrawal of calcitriol treatment may have been due to the long duration of treatment and the marked PTH suppression during treatment.

Adult↗
PubMed1999

Reproducibility of plasma angiotensin-converting enzyme activity in human subjects determined by fluorimetry with Z-phenylalanine-histidyl-leucine as substrate.

Despite the major physiologic role of angiotensin-converting enzyme (ACE), few studies have evaluated the ideal conditions for measuring human plasma ACE activity, specifically when using Z-phenylalanine-histidyl-leucine as substrate. This study, performed in volunteer patients, assessed the reproducibility of human plasma ACE activity measured by fluorimetry with Z-phenyl-histidyl-leucine as the substrate. After blood centrifugation, plasma was stored under different conditions until processing. The following sources of variability were evaluated: (1) the interval to centrifugation of blood after collection, (2) the temperature and (3) safe time for storing the plasma after cold centrifugation, (4) the effect of fasting. Plasma ACE activity was 20.6+/-7.7 U/mL, 20.9+/-8 U/mL, and 20.5+/-7.9 U/mL (n = 25) when samples were centrifuged immediately, after 1 hour of blood sampling, and after 3 hours of blood sampling, respectively (not significant). In plasma kept at -20 degrees C, ACE activity was not different after 1 week (17.4+/-4.3 U/mL) nor after 1 month (17.9+/-4 U/mL), whereas baseline ACE was 16.7+/-4.3 U/mL (n = 10). In plasma stored at -80 degrees C, ACE activity was 15.5+/-5.7 U/mL after 1 month (baseline 15+/-5.3 U/mL; not significant; n = 12). No evidence for hydrolysis of the reaction product of ACE (his-leu dipeptide) was observed in plasma samples kept for 1 month at -20 degrees C or at -80 degrees C (by high-performance liquid chromatography analysis). In plasma obtained before breakfast, ACE activity was 12.8+/-7.1 U/mL, and it was 12.3+/-7.5 U/mL 2 hours afterwards (not significant; n = 12). Thus, to determine human plasma ACE activity by fluorimetry with reliability, with Z-phenylalanine-histidyl-leucine used as a substrate, there is a safe interval of at least 3 hours before blood centrifugation at -4 degrees C. Plasma may be kept at -20 degrees C or at -80 degrees C for at least 4 weeks before final processing. Fasting does not influence its enzymatic activity.

Blood Preservation↗
PubMed1999

Prevalence of the angiotensin I converting enzyme insertion/deletion polymorphism, plasma angiotensin converting enzyme activity, and left ventricular mass in a normotensive Chilean population.

The aim of this study was to estimate the prevalence of the different alleles of the angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and associated plasma ACE activity, as well as cardiac echocardiographic structure, in a healthy Chilean population. We selected 117 healthy normotensive subjects (aged 45 to 60 years, middle socioeconomic status, nonobese, and nondiabetic) from a population-based study concerning the prevalence of risk factors for chronic diseases (Conjunto de Acciones Para la Reducción Multifactorial de las Enfermedades no Transmisibles [CARMEN]). The frequencies of the I and D alleles were 0.57 and 0.43, respectively. Mean plasma ACE activity was 15.3 +/- 3.9 U/mL. Compared with subjects with the II genotype, plasma ACE activity was significantly higher in subjects with the ID and DD genotypes with no difference between them. No correlation was observed between blood pressure and plasma ACE activity. Among the three different genotypes there was no difference in left ventricular (LV) dimensions or in LV mass. No correlation between plasma ACE activity and LV mass was observed for either gender or different genotypes. Multivariate linear regression analysis using LV mass and LV mass index as dependent variables showed independent effects (P < .05) for gender (higher LV mass in men) and diastolic blood pressure, but not for the DD genotype. In conclusion, in this population, the presence of the D allele on the ACE gene determined higher circulating ACE activity. However, in this normotensive healthy population, male gender and diastolic blood pressure, but not the presence of the D allele, were associated with increased LV mass.

Alleles↗
PubMed1999

Formulation factors affecting drug release from poly(lactic acid) (PLA) microcapsule tablets.

A sustained-release (SR) formulation of phenobarbital (PB) microcapsule tablet was prepared using low molecular weight (MW) DL- and high MW L-poly(lactic acid) (PLA) polymer. Microencapsulation of PB showed a unimodal size distribution (375 to 550 microns) of the microcapsules with high loading capacity (> 84%). Drug release from the microcapsule was influenced by the polymer ratios and increased with an increase in L-PLA amount. Microcapsules and physical mixtures of PB and the PLA were directly compressed independently to form microcapsule and matrix tablets, respectively. Drug release from the microcapsule tablets was significantly lowered (p < .001) compared to matrix tablets or free microcapsule (free microcapsule > matrices > microcapsule tablets). We also investigated the effect of tablet adjuvants, compression pressures, and microcapsule loading on the tablet performance in terms of friability, hardness, porosity, tensile strength, and the release kinetics of PB. The drug release rate increased with increasing compression pressure in the case of Emcompress or lactose, but not Avicel. The drug release rate was three- to fivefold increased with sodium starch glycolate compared to tablets without a disintegrant. With an increase in microcapsule loading, a decrease in the drug release rate was observed; however, the tablet performance remained satisfactory. The morphology of the microcapsules was monitored microscopically after the dissolution and the disintegration of tablets. The drug release accelerated with compression pressures and microcapsule loading from the tablets due to mechanical destruction of the microcapsule wall, which was more clearly seen after disintegration and dissolution of the tablets. Our data suggest that the PLA microcapsule can be tableted to make a SR product without significantly affecting its release kinetics.

Capsules↗
PubMed1998

Renal protection in patients undergoing cardiopulmonary bypass with preoperative abnormal renal function.

UNLABELLED: We prospectively studied the effects of renal protection intervention in 17 patients with preoperative abnormal renal function (plasma creatinine > 1.5 mg/dL) scheduled for elective coronary surgery. Patients were randomized to either dopamine 2.0 micrograms.kg-1.min-1 (Group 1, n = 10) or perfusion pressure > 70 mm Hg during cardiopulmonary bypass (CPB) (Group 2, n = 7). Glomerular filtration rate and effective renal plasma flow were measured with inulin and 125I-hippuran clearances before the induction of anesthesia, after sternotomy and before CPB, during hypo- and normothermic CPB, after sternal closure, and 1 h postoperatively. Plasma and urine electrolytes were measured, and free water, osmolar, and creatinine clearances, as well as fractional excretion of sodium and potassium, were calculated before and after surgery. Significant differences between groups were found before CPB for glomerular filtration rate (higher in Group 1), urine output (2.0 vs 0.29 mL/min in Group 1 versus Group 2), urinary creatinine (66 vs 175 mg/dL), urinary osmolarity (370 vs 627 mOsm/L), osmolar clearance (2.1 vs 0.7 mL/min), and urinary potassium (33 vs 71 mEq/L). There were no differences between groups during hypo- and normothermic CPB. After CPB, the only difference was a slightly higher urinary creatinine in Group 2. Renal plasma flow was lower than normal in all patients before the induction of anesthesia. A nonsignificant trend toward increased flow was seen during hypothermic CPB. Filtration fraction was high before CPB, which suggests efferent arteriolar vasoconstriction, descending toward normal during and after CPB. The same pattern of changes was present in both groups. In conclusion, there were no clinically relevant differences between the two treatment modalities during and after CPB. However, significant differences were observed before CPB, when dopamine seemed to partially revert renal vasoconstriction. IMPLICATIONS: Two protective interventions were compared in patients undergoing heart surgery to prevent deterioration of renal function; these were dopamine infusion throughout the operation and phenylephrine infusion during cardiopulmonary bypass. We found clinically relevant differences only during surgery before cardiopulmonary bypass.

Aged↗
PubMed1998

In vitro release of theophylline from poly(lactic acid) sustained-release pellets prepared by direct compression.

Poly(L-lactic acid), (L-PLA) pellets containing theophylline as a model drug were prepared with increasing bovine serum albumin (BSA) load of 10, 20, 30, 40, or 50% by direct compression. The drug release from pellets was studied in phosphate buffered saline (PBS, pH 7.4) at 37 degrees C. The annealing effect on theophylline release from pellets was also studied at 20, 30, 60, and 80 degrees C. In all cases, release kinetics followed the Higuchian mechanism with an initial burst effect followed by sustained release of theophylline during the experimental period. Increasing BSA load resulted in a linear increase in Higuchian release rates presumably because of the hydrophilic nature of BSA. Furthermore, BSA did not interact chemically with the polymer matrix and was held physically by the dense polymer matrix. However, drug release decreased with an increase in annealing temperature. Release of theophylline was higher from PLA-BSA combination pellets compared to PLA pellets at temperatures below the glass transition temperature (Tg) of the polymer and lower for temperatures above Tg. The temperature effect on drug release may be attributed to both the reduction of core solubility in the bulk phase and the lowering of diffusibility of the polymeric membrane. No drug-polymer interactions or polymer degradation was observed within the experimental setup when studied by differential scanning calorimetry (DSC), infrared (FTIR) spectroscopy, and gravimetric methods. DSC studies of pellets showed no hints of microstructural changes (crystallinity) of the polymers. In our experiments, theophylline was released primarily by leaching through channels and not by polymer degradation. The release rate was dependent on BSA loading and annealing. It may be concluded that PLA pellets can be fabricated suitably using BSA and annealing to design sustained-release preparations of water-soluble drugs.

Administration, Oral↗
PubMed1998

Effect of physicochemical factors on the release kinetics of hydrophilic drugs from poly(L-lactic acid) (L-PLA) pellets.

Poly(L-lactic acid) (L-PLA) pellets intended for either parenteral or oral use were successfully prepared by a direct compression technique without the use of heat or organic solvents. Salicylic acid and theophylline were chosen as drug candidates. The drug release from pellets was affected by the compression pressure. The Higuchi plots of the drugs showed a t1/2 dependent drug release pattern. The release rates of these drugs from PLA pellets were directly correlated to their solubilities in the dissolution media. At lower pH (< 7), the release of salicylic acid was found to be slower than theophylline; however, at higher pH (> 7), the release of salicylic acid was faster than that of the theophylline. The release rate of salicylic acid was higher at higher pHs, which was related to the increase in solubilities. Pellets were annealed at 20, 40, and 80 degrees C. A lower release rate was observed with increasing temperatures. Above the glass transition temperature (Tg) of the polymer, the release of drugs was significantly decreased. The drug release was independent of the ionic strength of the media for both salicylic acid and theophylline. We showed earlier that no drug-polymer interactions or polymer degradation were observed when studied by differentials scanning calorimetry (DSC) and infrared spectroscopy (IR) (1). The release mechanism was primarily physical diffusion and leaching during the experimental period. We conclude that the release of low molecular weight (MW) drugs from the high MW L-PLA was independent of the pH and the ionic strength of the dissolution media, but was dependent on the polarity of the drug and formulation factors, such as compression pressure and annealing temperature.

Administration, Oral↗
PubMed1995

Effects of extracorporeal circulation on renal function in coronary surgical patients.

We prospectively studied perioperative changes of renal function in 12 previously normal patients (plasma creatinine < 1.5 mg/dL) scheduled for elective coronary surgery. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured with inulin and 125I-hippuran clearances before induction of anesthesia, before cardiopulmonary bypass (CPB), during hypo- and normothermic CPB, after sternal closure, and 1 h postoperatively. Renal and systemic vascular resistances were calculated. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and plasma and urine electrolytes were measured, and free water, osmolal, and creatinine clearances, and fractional excretion of sodium and potassium were calculated before and after surgery. 125I-hippuran clearance was lower than normal in all patients before surgery. During hypothermic CPB, ERPF increased significantly (from 261 +/- 107 to 413 +/- 261 mL/min) and returned toward baseline values during normothermia. GFR was normal before and after surgery and decreased nonsignificantly during CPB. Filtration fraction was above normal before surgery and decreased significantly during CPB (0.38 +/- 0.09 to 0.18 +/- 0.06). Renal vascular resistance (RVR) was high before surgery and further increased after sternotomy (from 18,086 +/- 6849 to 30,070 +/- 24,427 dynes.s.cm-5), decreasing during CPB to 13,9647 +/- 14,662 dynes.s.cm-5. Urine NAG, creatinine, and free water clearances were normal in all patients both pre- and postoperatively. Osmolal clearance and fractional excretion of sodium increased postoperatively from 1.54 +/- 0.06 to 12.47 4/- 11.37 mL/min, and from 0.44 +/- 0.3 to 6.07 +/- 6.27, respectively. We conclude that renal function does not seem to be adversely affected by CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Renal scintigraphy with captopril in the evaluation of renovascular hypertension].

The administration of an angiotensin-converting enzyme (ACE) inhibitor transitorily reduces the GFR in a kidney with renal artery stenosis, effect that can be ascertained with scintigraphic studies using ACE inhibitors. We evaluated the clinical usefulness of captopril renography (CR) in the diagnosis of renovascular hypertension (RVH) in 51 hypertensive patients in which this diagnosis was suspected. All subjects underwent angiography and RVH was diagnosed when renal artery stenosis exceeded 60%, there was lateralization of renal vein renin or there was a concordant clinical outcome. Renography was performed 15 minutes after Lasix administration, using Tc-99m DTPA, before and 60 minutes after the oral administration of 50 mg of captopril. The scintigraphic criteria for a positive test were a decreased split renal function, a delayed peak uptake, a decreased excretion of DTPA and a prolonged transit time. In three of 28 patients in whom angiography discarded RVH, CR was positive. In the 23 patients with confirmed RVH, CR was positive in 10 of 12 with unilateral stenosis, in 3 of 8 with bilateral stenosis and 1 of 3 with stenosis in a transplanted kidney. The overall sensitivity and specificity of the test for RVH was 60.9% and 89.2% respectively. There were no changes in blood pressure or adverse effects after captopril administration. We conclude that CR in RVH is useful to select patients for further studies (angiography) and to perform a functional interpretation of angiographic alterations.

Adolescent↗
PubMed1993

[Aluminum-related bone disease in chronic hemodialysis patients].

Plasma aluminum (pAl) was measured in 58 patients coming from three centers using different preparation of dialysis water: deionizer (29 patients), softener (16 patients) and reverse osmosis (13 patients). Twenty five healthy subjects were used as controls. A deferoxamine test was performed to 11 of 19 patients with pAl between 40 and 200 micrograms/dl and a bone biopsy with double tetracycline staining was executed to 15 patients with pAl over 40 micrograms/dl. Mean pAl was 9.5 +/- 1.7 micrograms/dl in controls and 34.3 +/- 6.1 169 +/- 27.8 and 50.8 +/- 10.3 micrograms/dl in patients coming form centers using deionizers, softeners and reverse osmosis respectively. Seventy six percent of patients coming from centers using deionizers and 85% of patients coming from centers with reverse osmosis had pAl below 40 micrograms/dl and all had values below 200 micrograms/dl. Plasma aluminum had a increase of over 200 micrograms/dl in 6 of 11 patients in which the deferoxamine test was performed. Six patients had a positive staining for aluminum in bone biopsies (three with basal pAl over 200 micrograms/dl and one with a increase in pAL after deferoxamine < 200 micrograms/dl). Of these, 2 patients had a mixed osteodystrophy and 4 a low turnover bone disease. Centers with deionizers and reverse osmosis had very low aluminum levels in dialysis water and five of six patients with aluminum levels related bone disease came from the center using softener.

Aluminum↗
PubMed1990

[Human recombinant erythropoietin (rH-EPO) in chronic hemodialysis patients].

We studied 7 patients on chronic hemodialysis before and after 12 weeks of therapy with human recombinant erythropoietin. The drug was administered intravenously, 3 times a week at doses increasing from 50 to 125 U/kg. Dialysis was performed for 4 hr, 3 times a week and no blood transfusions were used during the study. An increased tolerance to daily physical activities was observed in all patients. Hematocrit increased from 19 +/- 3.4 to 28 +/- 4.1 and hemoglobin from 6.7 +/- 1.3 to 9.4 +/- 1.5, p less than 0.01. No changes were detected in blood pressure, weight, liver function tests and nutritional values. No patient developed either absolute (ferritin less than 30 ng/ml) or relative iron deficiency (transferrin saturation less than 20%) during the study. Efficiency of dialysis remained unaltered. No secondary effects from the drug were observed. Thus, this study confirms the clinical usefulness of human recombinant erythropoietin in patients with chronic renal failure and anemia on chronic dialysis.

Adult↗
PubMed1990

[Myelodysplasias: clinical experience with 35 patients].

Myelodysplasia, characterized by varied reductions of peripheral blood elements with normal or hypercellular bone marrow, is relatively frequent among older patients and may evolve to acute leukemia. We reviewed findings in 35 patients whom, according to the FAB classification were distributed as follows: simple refractory anemia (RA) 34%, sideroblastic refractory anemia (SRA) 14%, refractory anemia with excess blast forms (RAEB) 31%, chromic myelomonocytic leukemia (CMML) 12% and refractory anemia with excess blast forms in transformation (RAEBT) 9%. Cytogenetic studies performed in 16 patients were abnormal in 5 (31%), all among patients with poor prognosis forms of the disorder. All patients had anemia; thrombopenia and neutropenia were more frequent in subtypes RAEB, CMML and RAEBT). Mean survival rate was 30 months, significantly greater in RA and SRA compared to the other groups. Infections and development of acute leukemia were the causes of death.

Actuarial Analysis↗
PubMedDate not supplied

Microencapsulation using poly(L-lactic acid). I: Microcapsule properties affected by the preparative technique.

Microcapsules were prepared using a poly (L-lactic acid) (L = PLA), mol. wt. 43,200, by an emulsification and solvent evaporation technique. Phenobarbitone (PB) was used as a reference drug, (core to polymer ratio, 1:1). Both the o/w and w/o emulsion system were investigated in order to study microcapsule properties affected by the preparative technique. In the o/w system, dichloromethane (DCM) was used to dissolve L = PLA and PB and the resulting solution was dispersed in 1 per cent aqueous gelatin solution. Subsequent evaporation of the DCM resulted in the formation of microcapsules. PB was found to be poorly encapsulated within microcapsules from this o/w system. PB content in the microcapsules was found to improve using PB saturated aqueous gelatin solution as the continuum. In the w/o system, acetonitrile (AN) was used as a solvent for L-PLA and PB and light liquid paraffin (LLP), containing 2 per cent w/w Span 40, as the continuous phase. PB loading in the microcapsules was found to be very high from this w/o system. Microcapsules from the o/w system were very small compared to microcapsules obtained from the w/o system. The morphology of the microcapsules and the surface properties were found to be affected distinctly by the two techniques. Microcapsules from the o/w system showed a smooth and less porous surface, whereas a highly porous surface containing embedded PB crystals was found in the microcapsules from the w/o system.

Capsules↗
PubMedDate not supplied

Microencapsulation using poly(DL-lactic acid). I: Effect of preparative variables on the microcapsule characteristics and release kinetics.

Poly(DL-lactic acid) (DL-PLA, molecular weight 20,500) microcapsules containing phenobarbitone (PB) as a reference core were prepared using a water/oil (W/O) emulsion system. Surface morphology, particle size and 'encapsulation efficiency' of the microcapsules prepared using different preparative variables have been investigated. Buffer pH 9 was used as a dissolution medium to determine the affect of preparative variables on the release rate from these microcapsules. With an increase in temperature of evaporation the microcapsule surface became increasingly irregular and porous, due to deposition of phenobarbitone crystals near the vicinity of the microcapsule surface leading to rapid release of the core. The normalized release rate was found to increase exponentially with an increase in the temperature of evaporation. Microcapsule morphology was also severely affected due to differences in polymer concentration in the disperse phase solvent. With the increase in polymer concentration, the microcapsule surface was found to be increasingly irregular and non-continuous, due to rapid precipitation of the polymer. Increased polymer concentrations also increased mean microcapsule diameter. The release rate increased with the increase in polymer concentration due to surface defects and did not exhibit a straight line correlation. When core loading was very high (e.g. C:P, 2:1 and 1:1), crystals of phenobarbitone appeared at the surface and these caused a very rapid burst effect. However, microcapsules containing a lower phenobarbitone content were found to follow t1/2 dependent release. The encapsulation efficiency was not seriously affected due to variations in temperature of preparation and polymer concentration. However, with the decrease in initial core loading the encapsulation efficiency of microcapsules was found to be reduced.

Chemical Phenomena↗