Mammary excretion of cannabidiol in rabbits after intravenous administration.

The present study examined the distribution of cannabidiol into milk after an intravenous bolus injection (3 mg kg-1) to lactating rabbits. Drug concentrations in milk and serum were measured by HPLC. Cannabidiol was excreted into milk rapidly and the drug levels in milk increased over a 4-24-h period following the maternal injection. The mean milk to serum concentration ratio was 25.9, indicating a significant accumulation of the drug in milk.

Kinetic interaction between fluoxetine and imipramine as a function of elevated serum alpha-1-acid glycoprotein levels.

The effect of elevated serum alpha-1-acid glycoprotein (AAG) levels on the pharmacokinetic interaction between imipramine and fluoxetine has been examined by utilizing a novel strain of transgenic mice which express serum AAG levels several times greater than normal. Before fluoxetine treatment, serum imipramine levels were approximately three times greater in transgenic mice than in control mice. Despite higher serum imipramine levels in transgenic mice, brain drug levels were lower than those found in control mice. Fluoxetine pre-treatment (20 mg kg(-1) for 5 days) resulted in an increase in serum imipramine levels in both groups of mice and the extent of the increase was greater in transgenic mice than in control mice (4.5-fold increase compared with 3.1-fold). Similarly, fluoxetine pre-treatment resulted in an increase in brain levels of imipramine in both groups of mice and the extent of the increase was greater in transgenic mice than in control mice (3.0-fold increase compared with 2.0-fold). Similar trends were observed for levels of desipramine in the serum and brain. Serum imipramine and desipramine levels did not correlate with their respective brain levels in the presence of elevated serum AAG levels before and after pre-treatment. These findings indicate that the extent of increases in imipramine and desipramine serum and brain levels are greater during elevated serum AAG states than during normal AAG states when imipramine is co-administered with fluoxetine.

Steady-state kinetics of imipramine in transgenic mice with elevated serum AAG levels.

PURPOSE: The effect of elevated serum alpha-1-acid glycoprotein (AAG) concentrations on the steady-state serum and brain levels of imipramine and its metabolite desipramine was assessed. This was approached using a novel strain of transgenic mice whose basal endogenous serum AAG levels were 8.6-fold elevated over normal. METHODS: Imipramine was administered by s.c. infusion or i.p., injection into transgenic and control mice. After drug administration, serum and whole brain were harvested and analyzed for imipramine and desipramine concentrations. Equilibrium dialysis was performed to determine the extent of imipramine protein binding in transgenic and control sera. Serum and brain samples were analyzed for imipramine and desipramine content by an established HPLC method with UV detection. RESULTS: At steady-state, the mean serum imipramine concentration was significantly higher in transgenic mice than in control mice (859.0 vs. 319.9 ng/ml). In contrast, the mean steady-state brain imipramine concentration was significantly lower in transgenic mice (3,862.6 vs. 7,307.7 ng/g). Similarly, in transgenic mice, the mean steady-state serum desipramine concentration was significantly higher (176.7 vs. 39.0 ng/ml) while the mean brain desipramine concentration was lower (243.0 vs. 393.5 ng/g). The serum unbound fraction of imipramine was 3-fold lower in transgenic mice (0.03 vs. 0.09). CONCLUSIONS: Elevated serum AAG impedes the transport of imipramine and desipramine into the brain. Further, in the presence of elevated serum AAG levels, imipramine and desipramine concentrations in the brain did not correlate with their respective concentrations in the serum.

Pharmacokinetics and antidepressant activity of fluoxetine in transgenic mice with elevated serum alpha-1-acid glycoprotein levels.

Fluoxetine, a novel selective serotonin reuptake inhibitor utilized in the treatment of depression, is avidly bound to serum albumin and alpha-1-acid glycoprotein (AAG). AAG is an acute phase protein, and its serum levels are elevated in a variety of pathophysiological conditions including inflammation, depression, cancer, and acquired autoimmune deficiency syndrome. Further, the pharmacokinetic disposition and pharmacological activity of several highly bound drugs have been reported to be significantly altered as a result of elevated serum AAG. We investigated the effects of elevated serum AAG levels on the pharmacokinetic disposition, antidepressant activity, and steady state profile of fluoxetine and its demethylated metabolite, norfluoxetine. This was approached utilizing a novel strain of transgenic mice that expressed genetically elevated serum AAG levels severalfold over those of control mice. Serum and brain drug concentrations were determined by HPLC after fluoxetine administration. In transgenic mice, the volume of distribution and the terminal elimination half-life of fluoxetine were significantly reduced. Further, significant reductions in brain-to-serum fluoxetine concentration ratios and antidepressant activity were observed in transgenic mice, despite having higher serum drug levels than control mice. This trend in the serum continued at steady state, and brain fluoxetine levels were significantly lower in transgenic mice. The results of this study provide valuable insights regarding the consequences of elevated serum AAG levels, often seen in several disease states, on the pharmacokinetic disposition of fluoxetine.

Quantification of fluoxetine and norfluoxetine serum levels by reversed-phase high-performance liquid chromatography with ultraviolet detection.

A rapid and sensitive high-performance liquid chromatography assay method was developed to determine serum fluoxetine and norfluoxetine levels by single extraction of 0.1 ml of serum with sodium hydroxide. The mobile phase (55% acetonitrile-45% distilled water containing 10 mM aqueous triethylamine) was used to separate fluoxetine and norfluoxetine (25-1000 ng/ml, using clomipramine as the internal standard) by ultraviolet detection at 226 nm. The inter- and intra-day variabilities of fluoxetine and norfluoxetine were 13-18%, and the recoveries of both drugs exceeded 89%. This assay method was applied to a pharmacokinetic disposition study of fluoxetine in mice.

Rapid microsample analysis of imipramine and desipramine by reversed-phase high-performance liquid chromatography with ultraviolet detection.

A rapid and highly sensitive HPLC assay method was developed to measure small amounts of imipramine and its major metabolite, desipramine. The assay involved simple extraction procedures using clomipramine as the internal standard. The mobile phase consisted of acetonitrile (60%) and 0.01 M triethylamine in distilled water (40%) with the pH adjusted to 3.0. Separations were achieved on a C18 column and the effluent measured for UV absorption at 260 nm. The chromatographic separation was excellent, with no interference from endogenous serum constituents. This assay was suitable for measuring drug concentrations in the range of 10-1000 ng/ml using a 0.1-ml serum sample. The method was applied to a drug disposition study in transgenic mice with increased plasma alpha 1-acid glycoprotein.

Altered disposition and antidepressant activity of imipramine in transgenic mice with elevated alpha-1-acid glycoprotein.

Imipramine is a tricyclic antidepressant known to be bound in the serum primarily by alpha-1-acid glycoprotein. The present study examined the effect of changes in serum alpha-1-acid glycoprotein levels on the pharmacokinetics and antidepressant activity of the drug by utilizing a novel set of transgenic mice in which the steady-state level of alpha-1-acid glycoprotein is significantly elevated over normal. The pharmacokinetic disposition was characterized after i.v. and i.p. injections in transgenic and control mice. In transgenic mice, there were significant decreases in the serum unbound fraction (0.62+/- 0.38 vs.2.48 +/- 0.43%), Vd (9.0 +/- 2.5 vs. 22.4 +/- 3.2 liters/kg), T1/2 (35.0 +/- 7.6 vs. 65.3 +/- 7.6 min) and fraction of dose excreted unchanged in urine (0.14 +/- 0.07 vs. 0.70 +/- 0.20%) with no significant alterations in systemic clearance (204.7 +/- 56.1 vs. 292.8 +/- 58.4 ml/min/kg) compared to control values. The antidepressant activity of imipramine was measured by a swimming-immobility test 30 min after either imipramine (30 mg/kg i.p.) or saline treatment. After saline treatment, there were no significant differences in the duration of swimming despair between transgenic (183 +/- 24 sec) and control (175 +/- 12 sec) mice. Imipramine treatment resulted in reductions in the duration of immobility in both transgenic (130 +/- 21 sec) and control (54 +/- 33 sec) mice. The extent of reduction was significantly less in transgenic animals than in control animals. These alterations in the antidepressant action appeared to correlate with the unbound drug concentration but not with the total drug concentration.

Elevated alpha-1-acid glycoprotein reduces the volume of distribution and systemic clearance of saquinavir.

The purpose of this study was to characterize the relationship between plasma protein binding and the pharmacokinetic disposition of saquinavir during a normal and elevated alpha-1-acid glycoprotein condition. The extent of plasma binding of [14C]saquinavir to human plasma, human albumin, and human alpha-1-acid glycoprotein was also assessed. Transgenic mice, which overexpress plasma alpha-1-acid glycoprotein, and control mice were given a single intravenous injection of saquinavir (10 mg/kg) and plasma samples were harvested as a function of time. The extent of [14C]saquinavir (0.5-30 microg/ml) plasma protein binding in each group of mice was determined by ultrafiltration. Plasma saquinavir concentrations from in vivo administration were determined by high performance liquid chromatography with tandem mass spectrometry. Saquinavir binding in human plasma and control mouse plasma was similar (approximately 3% unbound). In contrast, the extent of binding was significantly increased in transgenic mice (1.5% unbound). Furthermore, saquinavir was more extensively bound to alpha-1-acid glycoprotein than to albumin (2.1 versus 11.5% unbound). The systemic clearance and volume of distribution of saquinavir were significantly reduced in transgenic mice compared with control mice. The results of this study show that alpha-1-acid glycoprotein is the predominant plasma protein to which saquinavir binds. In addition, elevations in plasma alpha-1-acid glycoprotein considerably alter the pharmacokinetic disposition of saquinavir. This is consistent with the observations that systemic exposure to saquinavir in human immunodeficiency virus patients is greater than that in healthy volunteers and that alpha-1-acid glycoprotein levels increase with the degree of HIV infection.