Drugs online research references
pharm.uoa.gr
The powder characteristics and the effect of the molecular weight of polymers as diluents on the release rate of furosemide and captopril from hard gelatin capsules were evaluated. The high molecular weight polymers studied were poly(oxyethylene) homopolymers (Polyox), with molecular weight ranging from 4,000,000 to 7,000,000. Powder characteristics suggested good flowability for these materials and predicted capsule fill weight uniformity. Swelling experiments showed a very high degree of swelling for these materials in both gastric and buffer solution. These polymers can sustain the release rate of both water-soluble and insoluble drugs from drug delivery systems. The low molecular weight polymers have a less pronounced sustained-release effect compared to the high molecular weight polymer material (i.e., those with 7,000,000 molecular weight). An increase in the content of polymer results in a decrease in the release rate of the drug. The solubility of the drugs clearly influenced the release rate. Release kinetics were evaluated and appeared to be influenced by the molecular weight of the polymer, the solubility of drug, and the ratio of the drug to polymer in the capsule. Bimodal release kinetics were exhibited by a number of furosemide formulations (i.e., F5 and F8).
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10934733&dopt=Abstract
Arch Mal Coeur Vaiss. 1986 Jun;79(6):929-32.
[Effect of inhibition of angiotensin converting enzyme on hypertension following kidney transplantation]
[Article in French]
Ribstein J, Mourad G, Argiles A, Mion C, Mimran A.
The activation of the renin angiotensin system is thought to be an important factor contributing to hypertension following kidney transplantation (TX). We studied 21 hypertensive renal transplant recipients, without evidence of acute graft rejection or transplant artery stenosis, 6 to 60 months post-TX. The acute responses of mean arterial pressure (MAP) and renal hemodynamics (ERPF: effective renal plasma flow, 131I-Hippuran clearance) and function (GFR: glomerular filtration rate, creatinine clearance; UNaV: urinary sodium excretion rate) to converting enzyme inhibition (CEI) by captopril were assessed. CEI induced a decrease in MAP (118 +/- 2 to 110 +/- 2 mmHg), renal resistance (RR: 0.27 +/- 0.02 to 0.21 +/- 0.01) and filtration fraction (FF: 0.31 +/- 0.02 to 0.23 +/- 0.01). ERPF (307 +/- 24 to 333 +/- 18 ml/min/1.73 m2) and GFR (88 +/- 5 to 78 +/- 5 ml/min/1.73 m2) were not significantly changed. UNaV increased by 53 +/- 24 mumol/min. Changes in MAP (r = -0.66), ERPF (r = 0.74) and FF (r = -0.88) were significantly correlated with the log of control plasma renin activity (PRA). In 10 patients with an increase of ERPF (range: + 30 to + 70%) and no change in GFR, the activated renin system could originate from the recipient's own kidneys. In the remaining 11 patients, CEI was associated with no increase in ERPF (change: + 2 to - 27%) and a fall in GFR, a response suggesting a possible intrarenal vascular damage. These results indicate that RAS participates in the regulation of systemic and renal vascular tone, with a possible predominant effect on efferent glomerular arteriole.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3099712&dopt=Abstract
lineone.net
BACKGROUND: Angiotensin Converting Enzyme inhibitors reduce mortality in heart failure. One therapeutic mechanism is believed to be the reduction of circulating angiotensin II and aldosterone. However, the Renin-Angiotensin-Aldosterone axis (RAAS) is not uniformly suppressed during therapy for heart failure. This effect has been referred to as 'angiotensin II reactivation' and 'aldosterone escape' and their reactivation may herald clinical deterioration. In the CONSENSUS I trial, correlations were seen between mortality, and angiotensin II and aldosterone. Furthermore, mortality was lower in those with good angiotensin II suppression. Therefore, neurohormonal elevation despite adequate treatment may associate with a poorer prognosis. AIMS: To follow chronic heart failure patients on ACE inhibitors for 18 months to assess whether or not angiotensin II and aldosterone reactivation are progressive with time, whether reactivation of both occurs simultaneously, and whether different ACE inhibitors have different neurohormonal profiles. METHODS AND RESULTS: We studied 22 patients (M/F 19:3, 72.5+/-7 years) on stable ACE inhibitors. Five times, in 18 months, samples were taken for neurohormones and ACE activity. Mean levels of neurohormones were remarkably stable over time, although captopril takers had generally higher angiotensin II, but lower aldosterone and renin. Aldosterone 'escape' (> 80 pg/ml) occurred in 13/97 samples (13.5%), in 5/22 (23%) individuals. Angiotensin II was elevated > or =10 pg/ml in 8/102 samples (8%), in 6/22 (27%) individuals. Four subjects had isolated angiotensin II reactivation, and three had aldosterone escape alone. On regression analyses between neurohormones in captopril takers there were significant correlations between; renin and angiotensin II (r = 0.62; P<0.02); angiotensin II and aldosterone (r = 0.6; P<0.02); and renin and aldosterone (r = 0.92; P<0.00001). CONCLUSION: In stable heart failure patients un-suppressed levels of angiotensin II and aldosterone occur despite therapy, but they are not necessarily progressive, nor simultaneous. Furthermore, contemporaneous serum ACE activity makes it unlikely the data presented reflects poor compliance. The results suggest that captopril takers may have different neurohormonal profiles, i.e. higher angiotensin II, and also better correlations between RAAS components, compared to longer acting preparations, although the numbers are small. Our data supports that of Swedberg et al. who showed reductions in both aldosterone and angiotensin II due to ACE inhibitor therapy, but no correlation between ACE activity and angiotensin II and only a limited correlation (r = 0.37) between angiotensin II and aldosterone. This suggests that the interaction between the components of the renin-angiotensin system is not simple and linear. The fact that each phenomenon appears to occur in isolation means that neurohormonal monitoring of individual could provide useful information to direct additional therapy. The RALES study has demonstrated reduced mortality from the addition of spironolactone to an ACE inhibitor emphasising the benefit of enhanced suppression of aldosterone in heart failure. Captopril may be less effective at suppressing the RAAS due to its short duration of action which would logically be associated with a more fluctuating pattern of ACE inhibition. In the presence of high levels of renin and angiotensin I even small differences in ACE activity will produce large variations in angiotensin II levels. Further studies should be directed at understanding the different mechanisms behind angiotensin II and aldosterone generation during ACE inhibition.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10937954&dopt=Abstract
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