Efficacy of pregabalin in the treatment of generalized anxiety disorder: double-blind, placebo-controlled comparison of BID versus TID dosing

Pregabalin: in the treatment of generalised anxiety disorder

Pregabalin, the pharmacologically active S-enantiomer of 3-aminomethyl-5-methyl-hexanoic acid, is a structural analogue of GABA, although it is not active at GABA receptors, nor does it acutely alter GABA uptake or degradation.black triangle Pregabalin binds with high affinity to the alpha2-delta subunit protein of voltage-gated calcium channels in CNS tissues and acts as a presynaptic modulator of the excessive release, in hyperexcited neurons, of various excitatory neurotransmitters. Binding of pregabalin to the alpha2-delta subunit appears necessary for its demonstrable anxiolytic, analgesic and anticonvulsant activities in animal models.black triangle Oral pregabalin, typically at dosages of 300-600 mg/day, was superior to placebo and similar to lorazepam 6 mg/day, alprazolam 1.5 mg/day and venlafaxine 75 mg/day in improving anxiety and depressive symptoms in patients with moderate-to-severe generalised anxiety disorder (GAD). Pregabalin had a rapid onset of anxiolytic activity relative to alprazolam and venlafaxine, which was evident after 1 week. Additionally, pregabalin (initial dosage 450 mg/day) was effective for the prevention of relapse of GAD over 34 weeks. Pregabalin was well tolerated during dosage escalation to fixed dosages (maximum 600 mg/day) over 7 days. Dizziness and somnolence, usually of mild to moderate severity, were the most common adverse events.black triangle The drug was not associated with a clinically significant medication withdrawal syndrome during a 1-week taper following 4 or 6 weeks' double-blind treatment.

Pregabalin: From molecule to medicine

Pregabalin, a compound with a novel mechanism of action (MOA), has demonstrated efficacy as an adjunctive treatment for epilepsy and in several neuropathic pain models. Multiple generalized anxiety disorder (GAD) clinical trials have shown that pregabalin has efficacy similar to the benzodiazepines and venlafaxine. Onset of anxiolytic effect was observed as early as Week 1 of treatment, and efficacy was seen in treating both psychic and somatic anxiety symptoms. Pregabalin binds potently and selectively to the alpha-2-delta subunit of "hyper-excited" voltage-gated calcium channels (VGCCs). The binding of pregabalin to VGCCs changes their conformation, reducing calcium influx at nerve terminals. Pregabalin only modulates the release of excitatory neurotransmitters in "hyper-excited" neurons, restoring them to normal physiological state. This newly defined MOA is believed to confer on pregabalin its anxiolytic, analgesic, and anticonvulsant properties. Thus, pregabalin may offer physicians an effective and well-tolerated therapy for GAD, which differs from existing treatments.

Activity profile of pregabalin in rodent models of epilepsy and ataxia

Pregabalin (Lyrica) is a novel amino acid compound that binds with high affinity to the alpha2-delta (alpha2-delta) auxiliary protein of voltage-gated calcium channels. In vivo, it potently prevents seizures, pain-related behaviors and has anxiolytic-like activity in rodent models. The present studies were performed to determine the profile of pregabalin anticonvulsant activity in a variety of mouse and rat models. In the high-intensity electroshock test, pregabalin potently inhibited tonic extensor seizures in rats (ED50 = 1.8 mg/kg, PO), and low-intensity electroshock seizures in mice. It prevented tonic extensor seizures in the DBA/2 audiogenic mouse model (ED50 = 2.7 mg/kg, PO). Its time course of action against electroshock induced seizures in rats roughly followed the pharmacokinetics of radiolabeled drug in the brain compartment. At higher dosages (ED50 1= 31 mg/kg, PO), pregabalin prevented clonic seizures from pentylenetetrazole in mice. In a kindled rat model of partial seizures, pregabalin prevented stages 4-5 behavioral seizures (lowest effective dose = 10 mg/kg, IP), and also reduced the duration of electrographic seizures. Pregabalin was not active to prevent spontaneous absence-like seizures in the Genetic Absence Epilepsy in Rats from Strasbourg (GAERS) inbred Wistar rat strain. Pregabalin caused ataxia and decreased spontaneous locomotor activity at dosages 10-30-fold higher than those active to prevent seizures. These findings suggest that pregabalin has an anticonvulsant mechanism different from the prototype antiepileptic drugs and similar to that of gabapentin except with increased potency and bioavailability. In summary, our results show that pregabalin has several properties that favor treatment of partial seizures in humans.

Anxiety states: a review of conceptual and treatment issues

PURPOSE OF REVIEW

The aim is to review studies published between August 2004 and July 2005, which address selected conceptual and treatment issues regarding various anxiety states.

RECENT FINDINGS

It remains unclear whether anxiety states are to be better conceptualized as several putatively distinct diagnostic entities or as one broadly conceived syndrome within which there are no clear boundaries between various manifestations of anxiety. The efficacy of selective serotonin reuptake inhibitors and venlafaxine in the treatment of anxiety states has been demonstrated by recent studies, but the comparisons between these agents did not show consistent advantages of one over the other. Novel medications for anxiety states, especially pregabalin, hold promise, but require further study. Cognitive-behavioural therapy for panic disorder is not only efficacious in controlled trials, but appears effective in routine clinical settings. A novel approach to the combined treatment of anxiety states may involve adding to behaviour therapy a medication that enhances associative learning.

SUMMARY

There is a need for further studies to improve conceptualization and classification of anxiety states. Optimal treatment approaches to anxiety states continue to involve cognitive-behavioural therapy and pharmacotherapy. Under certain circumstances, careful combinations of these basic treatment modalities may produce further benefits.

A double-blind, placebo- and positive-internal-controlled (alprazolam) investigation of the cognitive and psychomotor profile of pregabalin in healthy volunteers

RATIONALE

Pregabalin potently and selectively binds to the alpha(2)-delta subunit of voltage-dependent calcium channels, reducing calcium influx and modulating release of downstream excitatory neurotransmitters, such as glutamate. Pregabalin has demonstrated robust efficacy for several disease states, but its neuropharmacology is still being elucidated.

OBJECTIVE

This study was conducted to evaluate the cognitive and psychomotor effects of oral pregabalin (150 mg t.i.d.) using alprazolam (1 mg t.i.d.) as a positive internal control and placebo.

METHODS

Twenty-four healthy volunteers were randomised to a double-blind, three-way crossover study. Each period consisted of 3-day double-blind treatment followed by 1 day of single-blind placebo. Psychometrics included tests of Choice Reaction Time (CRT), CNS arousal (Critical Flicker Fusion, CFF), vigilance (Rapid Visual Information Processing, RVIP), serial memory scanning (Sternberg Short-Term Memory Scanning Test, STM), divided attention (Compensatory Tracking Task, CTT), Brake Reaction Time (BRT) in an on-the-road vehicle, and subjective Line Analogue Rating Scales (LARS) for sedation.

RESULTS

Pregabalin showed no significant effects on the objective psychometrics-CRT, BRT, RVIP, STM-compared with placebo. Pregabalin produced a limited, significant decrement on CFF and CTT and a significant effect on the LARS. Pregabalin was associated with improvement relative to placebo in BRT. The positive control, alprazolam, produced significant impairment on all objective measures and significant impairment on the LARS, thus establishing the sensitivity of the test battery used in the study.

CONCLUSIONS

Pregabalin did not differ on most assessments from placebo, producing only minor, transient impairment on some objective cognitive and psychomotor measures, suggesting a relatively benign CNS side-effect profile.

Pregabalin: a new neuromodulator with broad therapeutic indications

OBJECTIVE

To review pregabalin's pharmacology, pharmacokinetics, efficacy, and adverse effects in the treatment of neuropathic pain, epilepsy, and anxiety.

DATA SOURCES

A MEDLINE search (1993-October 2005) for peer-reviewed English-language publications was performed. Abstracts from professional meetings were also included. Key terms were anxiety, diabetic neuropathy, epilepsy, neuropathic pain, postherpetic neuralgia, pregabalin, and seizures.

STUDY SELECTION AND DATA EXTRACTION

Basic pharmacology data were extracted from animal studies; pharmacokinetic data were extracted from human studies. Multicenter, double-blind, placebo-controlled, parallel-group studies were included to describe the efficacy and adverse effects of pregabalin.

DATA SYNTHESIS

Pregabalin is a new agent that exerts its pharmacodynamic effect by modulating voltage-gated calcium channels. Pregabalin has a linear pharmacokinetic profile. It is completely absorbed, not bound to plasma proteins, not metabolized, and eliminated unchanged through the kidneys. Doses must be adjusted in patients with renal insufficiency. Clinical trials showed that pregabalin is effective in neuropathic pain associated with postherpetic neuralgia, diabetic peripheral neuropathy, in partial epilepsy as adjunctive therapy, and in generalized and social anxiety disorders. The most common adverse effects were dizziness and somnolence. Few serious adverse effects were reported. Pregabalin should not be discontinued rapidly.

CONCLUSIONS

Pregabalin is an effective and safe analgesic, antiepileptic, and anxiolytic medicine. It will provide a new treatment option for patients with neuropathic pain and partial epilepsy.