Posted by ed_uk on November 19, 2004, at 8:34:43
In reply to Re: ANYONE IN UK TAKING ANY BENZOS ? » ed_uk, posted by darkhorse on November 19, 2004, at 4:56:31
Hi Adam!
Yes, after a single dose, lorazepam lasts longer than diazepam, probably because lorazepam is less lipid soluble and less rapidly re-distributed. After repeated doses, diazepam lasts longer because of it's much longer half life. For me, a single oral dose of diazepam works within an hour and lasts about 90 mins followed by mild residual drowsiness and feelings of sadness. An isolated oral dose of lorazepam works within about 2 hours and lasts about 8 hours for me.
Read this...............
J Pharmacol Exp Ther. 1989 Jul;250(1):134-40. Related Articles, Links
Kinetic and dynamic study of intravenous lorazepam: comparison with intravenous diazepam.Greenblatt DJ, Ehrenberg BL, Gunderman J, Scavone JM, Tai NT, Harmatz JS, Shader RI.
Department of Psychiatry, Tufts University School of Medicine, Boston, Massachusetts.
Six healthy volunteers received a single i.v. dose of 'low dose' lorazepam (0.0225 mg/kg), 'high dose' lorazepam (0.045 mg/kg) and placebo by 1-min infusion in a double-blind three-way crossover study. Plasma concentrations were measured 24 hr after dosage, and the EEG power spectrum was simultaneously computed by fast-Fourier transform to determine the percentage of total EEG amplitude occurring in the 13-30-Hz range. Low and high dose lorazepam did not differ significantly in distribution volume (1.89 versus 1.81 l/kg) or elimination half-life (11.5 versus 12.2 hr); clearance was slightly although significantly reduced at the higher dose (2.08 versus 1.88 ml/min/kg, P less than .005). EEG effects were of relatively slow onset, reaching their maximum change over baseline 30 min after infusion. The duration of action was prolonged, with the fraction of EEG activity in the 13-30-Hz range still significantly above baseline **8 hr** after the 0.045 mg/kg dose. Five of these subjects received 0.15 mg/kg of i.v. diazepam in a companion study of identical design. ***EEG effects of diazepam were shorter than those of lorazepam, probably because of the more rapid and extensive decline in plasma diazepam concentrations*** in the postinfusion distribution phase. In addition, the onset of diazepam's effect was immediate. In male CD-1 mice that received i.v. diazepam (8.3 mg/kg) or lorazepam (3.3 mg/kg), the brain:plasma concentration ratio was maximal 2.5 min after dosage for diazepam, but equilibration was delayed at least 30 min after dosage for lorazepam. Thus the slow onset of action of lorazepam is probably attributable to slow entry into brain.
Ed
poster:ed_uk
thread:416677
URL: http://www.dr-bob.org/babble/20041118/msgs/417833.html