Effect of subcutaneous naratriptan on forearm blood flow.

This randomized, double-blind, placebo-controlled, four-way crossover study was conducted on an in-clinic basis to assess forearm perfusion after subcutaneous (s.c.) naratriptan and placebo by reserve volume (hyperemic/baseline) and basal forearm blood flow (FBF) measured by strain gauge plethysmography. Nineteen male and female volunteer migraine subjects (International Headache Society criteria) received s.c. naratriptan 1 mg, 5 mg, 10 mg, and placebo on four separate study days outside a migraine attack. FBF was recorded at baseline, at 7-min intervals post-dose up to 1 h (basal) and once after sublingual glyceryl trinitrate administered at 1 h (hyperemic). Vital signs and electrocardiograms were recorded at baseline and 15, 30, 45, and 60 min post-dose. There were no statistically significant differences in reserve volume (hyperemic/baseline) between any dose of s.c. naratriptan and placebo. The naratriptan to placebo ratio was 102% (95% CI: 87-120%; p = 0.789) for 1 mg; 97% (95% CI: 83-114%, p = 0.737) for 5 mg; and 92% (95% CI: 79-108%; p = 0.325) for 10 mg. There were no statistically significant differences in basal FBF for any dose compared to placebo. The naratriptan to placebo ratio was 95% (95% CI: 87-104%; p = 0.263) for 1 mg; 94% (95% CI: 86-102%; p = 0.142) for 5 mg; and 94% (95% CI: 86-103%; p = 0.157) for 10 mg. The percentage of patients reporting adverse events was 53% with placebo, 53% with s.c. naratriptan 1 mg, 89% with 5 mg and 89% with 10 mg. In conclusion, these results suggest that s.c. naratriptan doses similar to and above the oral therapeutic dose equivalent (single oral dose 2.5 mg) have no significant effect on peripheral blood flow as measured by FBF. S.c. naratriptan doses 1 mg, 5 mg, and 10 mg were well tolerated.

Pharmacokinetics and food interaction of MK-462 in healthy males.

A study was conducted to assess the safety, tolerability, and pharmacokinetics of single intravenous (IV) doses of 5-90 micrograms kg-1 of MK-462, and the effect of food on the pharmacokinetics of MK-462 administered orally to healthy males. Results of this study indicate that IV doses of MK-462 from 5 to 90 micrograms kg-1 are well tolerated. The disposition kinetics of MK-462 were linear for IV doses up to and including 60 micrograms kg-1. The values of the plasma clearance (CL), steady-state volume of distribution (Vss), plasma terminal half-life (t1/2), and mean residence time in the body (MRT) of MK-462 averaged 1376 mL min-1, 140 L, 1.8 h, and 1.7 h, respectively, and remained essentially constant over the dosage range of 10-60 micrograms kg-1 of IV MK-462. However, as the dose increased from 60 to 90 micrograms kg-1, the mean value of the apparent CL decreased from 1376 to 807 mL min-1. Thus, elimination of MK-462 was dose dependent in this dosage range. Based on the disposition decomposition analysis (DDA), it was shown that the Vss value of MK-462 remained essentially constant over the dosage range of 10-90 micrograms kg-1 of IV MK-462. The following values of two dose-independent parameters were also calculated by using DDA: distribution clearance (CLd) = 2028 mL min-1, and mean transit time in the peripheral tissues (MTTT) = 0.74 h. The mean values of AUC, Cmax, tmax, and apparent t1/2 of MK-462 in 12 subjects each receiving a 40 mg tablet of MK-462 without breakfast were 330 ng.h mL-1, 77 ng mL-1, 1.6 h, and 1.8 h, respectively. Although administration of a standard breakfast prior to dosing increased the AUC value (by approximately 20%) of MK-462 and delayed its absorption, there were no significant effects of the meal on the values of Cmax and apparent t1/2 of MK-462.

L-692,429, a nonpeptide growth hormone (GH) secretagogue, reverses glucocorticoid suppression of GH secretion.

The reversal of glucocorticoid-induced negative nitrogen balance by GH supports a possible therapeutic role for GH treatment in patients receiving these catabolic steroids. A GH secretagogue might be of similar utility. However, stimulated GH secretion is generally suppressed by glucocorticoids. To test whether L-692,429, a nonpeptide mimic of GH-releasing peptide-6, can overcome such suppression, a double blind, placebo-controlled, three-period, cross-over study was performed in nine healthy young men who received 0.2 mg/kg L-692,429, i.v., preceded by 4 days of prednisolone (20 mg, orally, three times daily) or placebo, and 0.75 mg/kg L-692,429 preceded by prednisolone only. The mean (SE) GH peak and area under the curve between 0-240 min after administration of 0.2 mg/kg L-692,429 in the absence of steroid were 53.8 (7.2) micrograms/L and 3481 (1005) micrograms/min.L, which were reduced to 25.1 (3.4) micrograms/L and 1342 (285) micrograms/min.L (P < or = 0.01) when treatment was preceded by 4 days of prednisolone. However, the suppressive influence of the steroid was attenuated by the high dose of L-692,429, which achieved a GH peak and area under the curve between 0-240 min of 42.6 (5.8) micrograms/L and 2298 (425) micrograms/min.L, respectively (P < 0.01 vs. 0.2 mg/kg L-692,429 plus prednisolone). L-692,429 stimulates GH secretion even in the setting of short term, high dose, concomitant glucocorticoid treatment, suggesting that such compounds might provide an alternative means of increasing circulating GH and reversing the catabolic effects of these steroids.

Blood pressure lowering and cerebral blood flow: a comparison of the effects of carvedilol and propranolol on the cerebral circulation in hypertensive patients.

The first part of this article concerns the general relation between blood pressure lowering and cerebral blood flow. Factors known to affect cerebral blood flow are reviewed, and recent advances in the field of innervation of cerebral blood vessels are outlined. Special emphasis is placed on the importance of the phenomenon of autoregulation and how this is disturbed in patients with hypertension. Not all antihypertensive drugs exert the same action on the cerebral circulation to produce the same blood pressure-lowering effect. In addition, the actions exerted by common antihypertensive drugs on the cerebral circulation are described. The second part of the article provides a comparison between the effect of carvedilol and that of propranolol on blood pressure reduction and cerebral blood flow. In a double-blind, crossover study involving 14 patients with mild-to-moderate hypertension, carvedilol was shown to have no effect on cerebral blood flow, whereas there was a slight tendency for lower flows to occur with the use of propranolol. Because of the small sample size, statistical significance was not reached. These results are consistent with other recently published findings.