Valaciclovir (Valtrex), the L-valyl ester of acyclovir, is undergoing clinical development for the treatment and suppression of herpesviral diseases. The absolute bioavailability of acyclovir from valaciclovir and the metabolic disposition of valaciclovir were investigated with healthy volunteers in two separate studies. In a randomized, crossover study, 12 fasting healthy volunteers each received 1,000 mg of oral valaciclovir and a 1-h intravenous infusion of 350 mg of acyclovir. The mean absolute bioavailability of acyclovir was 54.2%, a value three to five times that obtained previously with oral acyclovir. A similar estimate of 51.3% was made from urinary recovery of acyclovir. In the second study, four fasting volunteers received a single oral dose of 1,000 mg of [ 14 C]valaciclovir. The majority of plasma radioactivity was accounted for by acyclovir, with very low plasma valaciclovir concentrations (mean maximum concentration of drug in plasma ‫؍‬ 0.19 M), which were undetectable after 3 h postdose. By 168 h, more than 90% of the administered radioactive dose was recovered, with approximately 46% in urine and 47% in feces. More than 99% of the radioactivity recovered in urine corresponded to acyclovir and its known metabolites, 9-(carboxymethoxymethyl)guanine and 8-hydroxy-9-[(2-hydroxyethoxy)methyl]guanine, with valaciclovir accounting for less than 0.5% of the dose. Acyclovir, but no valaciclovir, was detected in fecal samples. These studies show that after oral administration to humans, valaciclovir is rapidly and virtually completely converted to acyclovir to provide a high level of acyclovir bioavailability in comparison with that following oral administration of acyclovir. The plasma acyclovir exposure obtained following oral administration of valaciclovir is similar to that achieved with doses of intravenous acyclovir, which are effective in the treatment and suppression of the less susceptible herpesviral diseases.

1 311C90 is a novel and selective agonist at 5-HTID receptors, with central and peripheral actions, currently in development for the acute oral treatment of migraine. 2 The pharmacokinetic and tolerability profiles of single oral doses from 1-50 mg 311C90 were investigated in 12 healthy male volunteers in a double-blind, placebo-controlled, dose-escalating study. 3 311C90 was well tolerated with most adverse experiences of mild and transient nature. 4 Absorption was rapid with dose-independent kinetics. Median t, , , was 2-4 h although 5 0 4 5 % of eventual C, , , was attained within 1 h. The tli2 was 2.5-3 h with a high apparent plasma clearance (CL/F> 2000 ml min-) and apparent volume of distribution ( V J F ) of 400-500 1. 5 Three metabolites were detected in plasma and urine, one of which, the N-desmethyl metabolite, has 5-HTID agonist activity. 6 311C90 showed no clinically significant effects on blood pressure, heart rate, ECG or laboratory variables at any dose and demonstrated a tolerability and pharmacokinetic profile compatible with an acute oral migraine treatment.

Two preliminary studies of the pharmacokinetics and tolerability of zolmitriptan nasal spray were conducted, each involving 12 healthy volunteers. In study 1, an initial double-blind, dose escalation phase (placebo or 2.5, 5.0, or 10 mg zolmitriptan intranasally) was followed by an open crossover phase in which all subjects received 10 mg zolmitriptan as a nasal spray, tablet, and oral solution. In study 2, subjects received, on three separate occasions, zolmitriptan 2.5 mg as an intranasal solution at pH 7.4, at pH 5.0, and as an oral tablet. In study 1, plasma concentrations of zolmitriptan and its active metabolite, 183C91, were broadly dose proportional. Plasma concentrations of zolmitriptan were detected earlier following nasal spray administration than after either tablet or oral solution. Similarly, in study 2, zolmitriptan was absorbed more rapidly following nasal spray administration with detectable plasma concentrations 5 minutes after dosing. Plasma levels were maintained at a plateau between 1 and 6 hours postdose, then decreased with a half-life of approximately 3 hours. There was no statistically significant difference for AUG or C(max) values between the two nasal spray solutions or between nasal spray and oral formulations. Other pharmacokinetic parameters for zolmitriptan were similar between the formulations. Plasma concentrations of 183C91 were higher for the first 2 hours after oral than after nasal spray administration. All formulations of zolmitriptan were well tolerated.

Aims Two open studies in healthy volunteers were conducted to determine the absolute bioavailability and metabolic disposition of zolmitriptan (311C90), a novel 5HT 1D agonist for the acute treatment of migraine. Methods After an initial test i.v. infusion, bioavailabilty was assessed by comparison of AUC after an i.v. infusion (3.5 mg ) and an oral tablet (10 mg), in six men and six women using a randomised, crossover design. Disposition was studied by administration of a 25 mg capsule, labelled with 100 mCi [ 14 C]-zolmitriptan, to five men and one woman on a single occasion. Results Zolmitriptan was well tolerated by both i.v. and oral routes. Adverse events were mostly mild, consistent with earlier studies and characteristic of this class of drug. Reports were similar in nature and number after both oral and iv dosing. Mean±s.d. oral bioavailability was 0.49±0.24 (0.38±0.16 in men and 0.60±0.28 in women). After oral dosing, C max and AUC values in women were approximately double those in men. Relative to zolmitriptan concentrations, metabolite concentrations were higher after oral dosing than after i.v., and higher in men compared with women. Half-life was significantly longer after oral dosing (mean 22%, 95% CI 6-35%). Mean±s.d. values for CL, V z and t 1/2,z after i.v. dosing (all subjects) were 8.7±1.7 ml min −1 kg −1 , 122±32 l and 2.30±0.59 h respectively. Following administration of 25 mg [ 14 C]-zolmitriptan, 91.5% of the dose was recovered in 7 days, 64.4±6.5% in urine and 27.1±6.0% in faeces. Less than 10% was recovered unchanged in urine, with 31.1±6.4% recovered as the inactive indole acetic acid metabolite. Most of the faecal material was unchanged zolmitriptan, representing unabsorbed drug. Plasma concentrations of [ 14 C] were slightly higher than those of the summed concentrations of known analytes zolmitriptan, the active N-desmethyl metabolite (183C91), the inactive N-oxide (1652W92) and indole acetic acid (2161W92) metabolites, which accounted for 86% of total plasma radioactivity. No other significant metabilites were detected in plasma. Some minor additional metabolites were detected in urine, none of which contributed more than 5% of the dose. Conclusions The data suggest that zolmitriptan undergoes first-pass metabolism and this is more extensive in men than in women. Zolmitriptan has suitable bioavailabilty for an acute oral migraine treatment and there are no significant unidentified metabolites in man.

Aims Zolmitriptan (Zomig (formerly 311C90)) is a novel 5-HT 1B/1D receptor agonist developed for the acute oral treatment of migraine. A highly sensitive LCMS-MS assay has been developed which allows quantification of plasma concentrations of zolmitriptan and its active metabolite, 183C91, after therapeutic doses. Two studies using this assay method were conducted to investigate the pharmacokinetics, including absolute bioavailability, of 2.5 and 5 mg oral doses of zolmitriptan in men and women, the dose-proportionality of 2.5, 5 and 10 mg doses and the effect of food on the pharmacokinetics of a 5 mg oral dose. Methods Two randomized, balanced, open-label, 4-period crossover studies were conducted in a total of 32 healthy volunteers. The first study determined the absolute bioavailability of 2.5 and 5 mg doses of zolmitriptan and compared the pharmacokinetics in men and women. The second study examined the doseproportionality in pharmacokinetics after fasting doses of 2.5, 5 and 10 mg, and the effect of food on a 5 mg dose. Blood pressure, heart rate, ECG, clinical chemistry, haematology and adverse events were also monitored. Results The mean (s.d.) absolute oral bioavailability was 0.41 (0.14 and 0.40) 0.09 after 2.5 mg and 0.48±0.14 and 0.36±0.07 after 5 mg in women and men, respectively. Without adjustment for bodyweight, plasma concentrations of zolmitriptan, but not 183C91, were higher in women than men. Mean (±s.d.) AUC was 32.7±10.1 and 60.2±26.8 ng ml −1 h after 5 mg in men and women, respectively (95% CI for ratio 0.43-0.77). After 2.5 mg mean (±s.d.) AUC was 18.4±5.4 and 23.1±9.9 ng ml −1 h in men and women, respectively (95% CI for ratio 0.61-1.09).However, these differences were of no clinical significance. C max and AUC of oral zolmitriptan were dose-proportional and there was a 13 and 16% fall in mean zolmitriptan C max and AUC, respectively, when administered after food. Adverse effects were minor, predominantly mild and transient, and there were no clinically significant effects on ECG, blood pressure, or laboratory parameters. Conclusions At therapeutic doses zolmitriptan has good oral bioavailability in healthy volunteers and has dose-proportional pharmacokinetics that are not affected by food to any clinically relevant extent.Keywords: bioavailability, food, pharmacokinetics, zolmitriptan from 6 to 50 mg in healthy volunteers have already been Introduction described [9]. The absolute bioavailability of a single 10 mg dose is 49% [10], compared with 14% reported for Zolmitriptan (Zomig, formerly 311C90) is a new 5-hydroxytryptamine (5-HT) 1B/1D receptor agonist [1] sumatriptan 100 mg [11]. Zolmitriptan is rapidly absorbed after oral administration but as plasma profiles show multiple developed for the acute oral treatment of migraine. Clinical studies have shown it to be effective and well tolerated in peaks in some subjects, individual t max values may vary from 0.5 to 5 h [6]. Zolmitriptan is eliminated mainly by the acute treatment of migraine at doses of 2.5-25 mg, with a headache respo...