Evaluation of the potential pharmacokinetic interaction between almotriptan and fluoxetine in healthy volunteers

The Herb-Drug Pharmacokinetic Interaction of Fluoxetine and Its Metabolite Norfluoxetine with a Traditional Chinese Medicine in Rats by LC-MS/MS

Background

Fluoxetine (FLU) is the first-line and widely used medication for depression. The combination of Chaihu Shugan san (CSGS) and FLU is commonly used to enhance antidepressant effects and reduce side effects.

Objective

The primary objective of this study was to investigate the potential pharmacokinetic effect of CSGS on FLU.

Materials and Methods

Thirty-two healthy adult male Sprague-Dawley (SD) rats were randomly divided into four groups, the fluoxetine group and multiple dose groups A, B, and C. The rats in the different groups were orally administered with a combination of FLU and different doses of CSGS for 14 d. On the fifteenth day, serial blood samples were taken from the caudal vein before the administration and at 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 10, 12, 24, 36, and 48 h after the administration. A liquid-liquid extraction method was applied to extract the analytes from serum. Then, the concentrations of FLU and its metabolite, norfluoxetine (NOF), were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The pharmacokinetic parameters were calculated by DAS 3.2.8 program and compared by statistic analysis.

Results

Compared with the FLU group, the FLU and NOF area under the plasma concentration-time curve (AUC) (0–∞) in multiple dose group C was significantly increased, while the NOF AUCs (0–∞) in multiple dose group A and multiple dose group B were decreased. Compared with the FLU group, the NOF clearance (CL) in multiple dose group C was decreased, while the CL in multiple dose groups A and B was increased.

Discussion and Conclusion

There were some differences in pharmacokinetic parameters between the FLU group and multiple dose groups, and CSGS can affect the pharmacokinetics of fluoxetine.

Almotriptan: a review of 20 years' clinical experience

Introduction: Almotriptan (ALT), a serotonin 5-HT_1B/1D agonist has been used in the acute treatment of migraine with or without aura for 20 years, accumulating data on more than 15,000 patients in studies and from an estimated >150 million treated migraine attacks in daily clinical practice. The last major review of ALT was written almost 10 years ago. The current narrative review provides an overview of the experience gained with almotriptan over that time, and highlights data published in the last decade. Areas covered: Randomized clinical trials, observational studies, postmarketing studies and meta-analyses involving ALT for the treatment of acute migraine identified through a systematic literature search. Expert opinion: Triptans are a mainstay of anti-migraine treatment. Findings with ALT over the last 10 years have reinforced the positive efficacy and tolerability results that were reported during the first 10 years following its introduction. In particular, more recent clinical results have confirmed its efficacy in women with menstrual migraine, the usefulness of early intervention, long-term benefit in adults, and also its efficacy and safety in adolescents. Overall, ALT can be considered an optimal choice for managing acute migraine resistant to first-line drugs.

Clinical Profile and Practice Experience of Almotriptan

Patients expect their acute migraine treatment to have a rapid onset of action, achieve complete pain relief that is sustained for 24 h, and to have a good tolerability profile. Almotriptan has a favourable pharmacokinetic profile that translates clinically to a rapid onset of action and consistent absorption regardless of age, sex, food intake and status of the acute migraine attack. In addition, almotriptan is not associated with any clinically relevant drug-drug interactions. Pain-free status at 2 h postdose is achieved by approximately 39% of patients receiving almotriptan in clinical trials. Recurrence of headaches within 24 h is low with almotriptan (< 22%). Almotriptan has a sustained pain-free rate of 25-27%, which in a meta-analysis of triptans was superior to sumatriptan 100 mg. Almotriptan therapy is associated with a low incidence of adverse events, including those affecting the central nervous system and chest.

Drug interactions with triptans : which are clinically significant?

The triptans are a group of compounds with high efficacy for the acute treatment of migraine and cluster headache. They have a relatively wide therapeutic index, and although a number of minor pharmacokinetic interactions have been observed, few are likely to be clinically significant. Given the differences in principal elimination pathways, potentially interacting drugs on a pharmacokinetic basis are not common across all compounds. Of more concern than pharmacokinetic interactions are pharmacodynamic interactions. Of most concern, additive vasoconstrictor effects are likely to occur with other vasoconstrictors, especially the ergots used for migraine. Serotonin syndrome has been observed due to coadministration of triptans with selective serotonin reuptake inhibitors (SSRIs), but the absolute rate of such a clinical response to coadministration is probably low. Most patients can take triptans with other medications without dose alteration, although vigilance is required for pharmacodynamic interactions.

Clinically significant drug interactions with newer antidepressants

After the introduction of selective serotonin reuptake inhibitors (SSRIs), other newer antidepressants with different mechanisms of action have been introduced in clinical practice. Because antidepressants are commonly prescribed in combination with other medications used to treat co-morbid psychiatric or somatic disorders, they are likely to be involved in clinically significant drug interactions. This review examines the drug interaction profiles of the following newer antidepressants: escitalopram, venlafaxine, desvenlafaxine, duloxetine, milnacipran, mirtazapine, reboxetine, bupropion, agomelatine and vilazodone. In general, by virtue of a more selective mechanism of action and receptor profile, newer antidepressants carry a relatively low risk for pharmacodynamic drug interactions, at least as compared with first-generation antidepressants, i.e. monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs). On the other hand, they are susceptible to pharmacokinetic drug interactions. All new antidepressants are extensively metabolized in the liver by cytochrome P450 (CYP) isoenzymes, and therefore may be the target of metabolically based drug interactions. Concomitant administration of inhibitors or inducers of the CYP isoenzymes involved in the biotransformation of specific antidepressants may cause changes in their plasma concentrations. However, due to their relatively wide margin of safety, the consequences of such kinetic modifications are usually not clinically relevant. Conversely, some newer antidepressants may cause pharmacokinetic interactions through their ability to inhibit specific CYPs. With regard to this, duloxetine and bupropion are moderate inhibitors of CYP2D6. Therefore, potentially harmful drug interactions may occur when they are coadministered with substrates of these isoforms, especially compounds with a narrow therapeutic index. The other new antidepressants are only weak inhibitors or are not inhibitors of CYP isoforms at usual therapeutic concentrations and are not expected to affect the disposition of concomitantly administered medications. Although drug interactions with newer antidepressants are potentially, but rarely, clinically significant, the use of antidepressants with a more favourable drug interaction profile is advisable. Knowledge of the interaction potential of individual antidepressants is essential for safe prescribing and may help clinicians to predict and eventually avoid certain drug combinations.

Almotriptan: a review of 10 years' clinical experience

Almotriptan, a serotonin 5-HT 1B/1D agonist, was developed for the acute treatment of migraine with or without aura and has been available for 10 years. This article evaluates the wealth of experience that has been obtained with almotriptan, including large randomized clinical trials (RCTs) and post-marketing studies that more closely reflect everyday clinical practice. Initial RCTs required patients to take almotriptan when migraine pain was of moderate or severe intensity, and found that 12.5 mg provided optimal outcomes for both pain relief and tolerability. Almotriptan effectively improved 2-h pain-relief, reduced migraine-associated symptoms and demonstrated low recurrence rates. These findings were also shown in patient subgroups, such as adolescents and menstrual migraineurs. A secondary finding in these trials was that patients who took almotriptan early, when the pain was still mild, achieved better outcomes. This prompted the initiation of studies designed to assess the effect of almotriptan in early intervention. Open-label trials reported improvements in pain-free end points (2 h, 24 h), and subsequent RCTs confirmed these findings. Pharmacovigilance data from more than 100 million tablets dispensed worldwide have confirmed that almotriptan is associated with a low occurrence of adverse effects, which, in clinical trials, has been shown to be similar to that observed with placebo. The clinical evidence obtained and comparisons made over a decade of use have demonstrated that almotriptan is one of the more effective and fast-acting triptans available, with a placebo-like tolerability profile. This suggests that almotriptan is an excellent choice for patients requiring specific acute migraine treatment.

Amine oxidases and monooxygenases in the in vivo metabolism of xenobiotic amines in humans: has the involvement of amine oxidases been neglected?

In this review, the major enzyme systems involved in vivo in the oxidative metabolism of xenobiotic amines in humans are discussed, i.e. the monooxygenases [cytochrome P450 system (CYPs) and flavin-containing monooxygenases (FMOs)] and the amine oxidases (AOs). Concerning the metabolism of xenobiotic amines (drugs in particular) by monoamine oxidases (MAOs), this aspect has been largely neglected in the past. An exception is the extensive investigation carried out on the inhibition of the metabolism of tyramine, when tyramine-containing food is ingested by subjects taking inhibitors of MAO A or of both MAO A and B. Moreover, investigations in humans on the metabolism of drug amines on the market by AOs, such as semicarbazide-sensitive amine oxidases (SSAOs) and polyamine oxidases (PAOs), are practically nonexistent, with the exception of amlodipine. In contrast to MAOs, monooxygenases (CYP isoenzymes more than FMOs) have been extensively investigated concerning their involvement in the metabolism of xenobiotics. It is possible that the contribution of AOs to the overall metabolism of xenobiotic amines in humans is underestimated or erroneously estimated, as most investigations of drug metabolism are performed using in vitro test systems optimized for CYP activity, such as liver microsomes, and most investigations of drug metabolism in vivo in humans carry out only the identification of the final, stable metabolites. However, for some drugs on the market, the involvement of MAOs in their in vivo metabolism in humans has been demonstrated recently, among these drugs citalopram, sertraline and the triptans are examples that can be mentioned.

Focus on trial endpoints of clinical relevance and the use of almotriptan for the acute treatment of migraine

Almotriptan is a 5-HT(1B/1D) receptor agonist, or triptan, indicated for the acute treatment of migraine. It has been shown to be effective and well tolerated for the treatment of acute migraine in approximately 5000 patients enrolled in short-term placebo- and active-controlled trials and long-term open-label trials. A recent meta-analysis reported that almotriptan has the highest sustained pain-free (SPF) rate and lowest adverse-event (AE) rate of all oral triptans. Sustained pain free is a composite endpoint of pain freedom at 2 h, no recurrence of moderate-to-severe headache and no use of rescue medication from 2 to 24 h after dosing. Patient surveys have indicated that migraine sufferers consider complete pain relief, no recurrence, rapid onset and no side-effects to be the most important attributes of their acute treatment. Composite endpoints such as SPF and SPF with no AEs (SNAE) contain the attributes that migraine sufferers express as being the most important elements of an acute migraine therapy, and their use in future clinical trials should aid in the selection of agents that can offer patients the highest likelihood of consistent treatment success.

Identification of the human liver enzymes involved in the metabolism of the antimigraine agent almotriptan

Almotriptan is a novel highly selective 5-hydroxytryptamine(1B/1D) agonist developed for the acute oral treatment of migraine. The in vitro metabolism of almotriptan has been investigated using human liver subcellular fractions and cDNA-expressed human enzymes, to study the metabolic pathways and identify the enzymes responsible for the formation of the major metabolites. Specific enzymes were identified by correlation analysis, chemical inhibition studies, and incubation with various cDNA expressed human enzymes. Human liver microsomes and S9 fraction metabolize almotriptan by 2-hydroxylation of the pyrrolidine group to form a carbinolamine metabolite intermediate, a reaction catalyzed by CYP3A4 and CYP2D6. This metabolite is further oxidized by aldehyde dehydrogenase to the open ring gamma-aminobutyric acid metabolite. Almotriptan is also metabolized at the dimethylaminoethyl group by N-demethylation, a reaction that is carried out by five different cytochrome P450s, flavin monooxygenase-3 mediated N-oxidation, and MAO-A catalyzed oxidative deamination to form the indole acetic acid and the indole ethyl alcohol derivatives of almotriptan. The use of human liver mitochondria confirmed the contribution of MAO-A to the metabolism of almotriptan. Both, the gamma-aminobutyric acid and the indole acetic acid metabolites have been found to be the major in vivo metabolites of almotriptan in humans. In addition, different clinical trials conducted to study the effects of CYP3A4, CYP2D6, and MAO-A on the pharmacokinetics of almotriptan confirmed the involvement of these enzymes in the metabolic clearance of this drug and that no dose changes are required in the presence of inhibitors of these enzymes.

Absolute bioavailability, pharmacokinetics, and urinary excretion of the novel antimigraine agent almotriptan in healthy male volunteers

Absolute bioavailability, pharmacokinetics, and urinary excretion of almotriptan, a novel 5-HT(1B/1D) receptor agonist, were studied in 18 healthy males following single intravenous (i.v.) (3 mg), subcutaneous (s.c.) (6 mg), and oral (25 mg) doses. Volunteers received each dose in a randomized sequence separated by a 7-day washout. Blood and urine samples for pharmacokinetic evaluations were taken for up to 24 hours after dosing. The disposition kinetics of almotriptan after i.v. and s.c. administration showed biphasic decline described by a two-compartment model. The fastest disposition phase was well observed, although estimates of the rate constant showed high variability. After s.c. administration of almotriptan, the bioavailability was 100% with a time to maximum plasma concentration (tmax) of 5 to 15 minutes, whereas after oral administration, the bioavailability was about 70% with a tmax of 1.5 to 3.0 hours. No significant differences were observed between administration routes in the elimination half-life (t(1/2), obtaining mean values ranging from 3.4 to 3.6 hours. The volume of distribution, total clearance, and t(1/2) indicated that almotriptan was extensively distributed and rapidly cleared from the body irrespective of dose or route of administration. The primary route of elimination was renal clearance (approximately 50%-60% of total body clearance). About 65% of the i.v. and s.c. dose and 45% of the oral dose were excreted unchanged in urine in 24 hours, with nearly 90% of this in the first 12 hours. Renal clearance was approximately 2- to 3-fold that of the glomerular filtration rate in man, suggesting that almotriptan is eliminated in part by renal tubular secretion.

Triptans

Triptans are potent serotonin (5-HT) 1B/1D receptor agonists used to abort and treat migraine headaches. Although the triptans share pharmacodynamic characteristics at 5-HT(1B/1D) receptors, they differ pharmacokinetically. This column reviews how the triptans are metabolized. Generally, the triptans are metabolized by phase I monoamine oxidases (MAOs) and by various cytochrome p450 enzymes. However, each triptan has a unique metabolic profile, leading to significant differences in each triptan's potential for drug-drug interactions. These differences are detailed in this review.

Almotriptan, a new anti-migraine agent: a review

Almotriptan is a new anti-migraine agent with nanomolar affinity for human 5-HT(1B), 5-HT(1D), and 5-HT(1F) receptors, weak affinity for 5-HT(1A) and 5-HT(7) receptors and no significant affinity for more than 20 other pharmacological receptors. Almotriptan was effective in animal models predictive of anti-migraine activity in humans and had a good safety profile in animal studies. From the toxicological point of view, almotriptan has a profile similar to that of other marketed triptans. In animal studies, at levels substantially higher than required for therapeutic activity in humans, almotriptan was devoid of any oncogenic, genotoxic or teratogenic effects. Almotriptan is well absorbed orally; its absolute bioavailability in humans is 70%. Its peak plasma levels are reached at 1 to 3 h after its administration; its elimination half-life is 3 to 4 h. Almotriptan is metabolized by monoamine oxidase-mediated oxidative deamination and cytochrome P450-mediated oxidation as the major metabolic route and by flavin monooxygenase as the minor route. No dose adjustment is required for gender or age, and only in the case of severe renal impairment the dose should not exceed 12.5 mg over a 24-h period. There was no significant interaction between a single dose of almotriptan and propranolol, fluoxetine or verapamil, at multiple doses. The efficacy of almotriptan in the treatment of acute migraine was demonstrated in clinical trials on more than 3000 patients with migraine. At two h after oral administration of almotriptan, 12.5 mg, the percentages of patients showing pain relief and a pain-free score were 64 and 36%, respectively. The effects of almotriptan were significantly better than those of placebo. When almotriptan was administered in the early phase of migraine, the percentage of pain-free patients at 2 h rose to 84%. In a phase III, double-blind and placebo-controlled study, the incidence of adverse events with almotriptan was not statistically different from that of placebo. Based on the available data, it appears that almotriptan is the triptan of choice when good efficacy and high tolerability are desired.

Almotriptan Malate

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Effect of MAO-A inhibition on the pharmacokinetics of almotriptan, an antimigraine agent in humans

AIMS

To assess the effect of a reversible MAO-A inhibitor, moclobemide, on the single-dose pharmacokinetics of almotriptan and assess the clinical consequences of any interaction.

METHODS

Twelve healthy volunteers received the following treatments in a randomized, open-label, two-way crossover design (with a 1 week washout between treatments): (A) one 150 mg moclobemide tablet every 12 h for 8 days and one 12.5 mg almotriptan tablet on the morning of day 8; and (B) one 12.5 mg almotriptan tablet on day 8. Plasma almotriptan was quantified by h.p.l.c.-MS-MS, while urinary concentrations were measured by h.p.l.c.-u.v. Vital signs, ECGs, and adverse events were evaluated after almotriptan administration. Treatment effects on pharmacokinetics and vital signs were assessed by analysis of variance.

RESULTS

Mean almotriptan AUC was higher (483 +/- 99.9 vs 352 +/- 75.4 ng ml-1 h, P = 0.0001) and oral clearance was lower (26.6 +/- 4.00 vs 36.6 +/- 5.89 l h-1, P = 0.0001) when almotriptan was administered with moclobemide. Mean half-life was longer (4.22 +/- 0.78 vs 3.41 +/- 0.45 h, P = 0.0002) after coadministration with moclobemide. Renal clearance of almotriptan was unaffected by moclobemide. No serious adverse events occurred and no clinically significant vital sign changes were observed.

CONCLUSIONS

Moclobemide increased plasma concentrations of almotriptan on average by 37%, but the combined administration of these two compounds was well tolerated. The degree of interaction was much less than that seen previously for sumatriptan or zolmitriptan given with moclobemide.