Dược Động Học :
▧ Absorption :
Readily absorbed with an absolute bioavailability of 90% when given orally. When intramuscularly administered, lorazepam is completely and rapidly absorbed. It achieves max serum concentration in 3 hours. The max serum concentration of a 4 mg dose is 48 ng/mL.
▧ Volume of Distribution :
1.3 L/kg. Unbound lorazepam can cross the blood-brain-barrier via passive diffusion.
▧ Protein binding :
91±2% bound to plasma proteins when given parenterally. When given orally, it is 85% bound to plasma proteins.
▧ Metabolism :
Lorazepam is hepatically metabolized and is extensively conjugated to the 3-0-phenolic glucuronide. This is an inactive metabolite and is eliminated mainly by the kidneys.
▧ Route of Elimination :
When a single 2 mg oral dose is give to healthy subjects, 88±4% of the administered dose was recovered in urine and 7±2% was recovered in feces. The percent of administered dose recovered in urine as lorazepam glucuronide was 74±4%. Only 0.3% of the dose was recovered as unchanged lorazepam, and the remainder of the radioactivity represented minor metabolites.
▧ Half Life :
Parenteral administration = 14±5 hours;
Oral administration = 2 hours.
▧ Clearance :
Total clearance, parenteral administration = 1.1±0.4 mL/min/kg.