Correlation between the experimental data from animal studies and therapetical effects of antidepressant drugs

Incidence of tricyclic antidepressant-like complications after cyclobenzaprine overdose

BACKGROUND

The cyclobenzaprine structure is similar to amitriptyline; however, tricyclic antidepressant (TCA)-like wide complex dysrhythmia has not been reported. Our objective was to determine the incidence of TCA-like effects in cyclobenzaprine overdoses as reported to 6 poison centers for 2 years. We compared the incidence of these effects to amitriptyline overdoses collected during the same period.

METHODS

We performed a retrospective review of 2 years of cases as reported to the Texas Poison Center Network. We identified sole ingestions of cyclobenzaprine and of amitriptyline. Cases had a recorded clinical outcome and clinical effect. A trained reviewer used a standard data collection sheet within a secured electronic database. One investigator audited a random sample of charts.

RESULTS

We identified 3974 cases of cyclobenzaprine calls. Of these, we collected 209 cases of acute overdoses without coingestions. There were no deaths. No cases of cyclobenzaprine ingestions were reported to have died or have a wide QRS or ventricular dysrhythmia. Seizures were reported in 2 cases; however, both were unrelated to cyclobenzaprine. Hypotension was reported in 1.4% (3/209) of cases, and a vasopressor was used in one case (0.5%). Patients with an amitriptyline overdose were more likely to have seizure, coma, tachycardia, a wide QRS or ventricular dysrhythmia, and have received sodium bicarbonate or be intubated.

CONCLUSIONS

Cyclobenzaprine overdoses were not reported to cause widened QRS, ventricular dysrhythmias, or seizures, and hypotension was rarely reported. Tricyclic antidepressant-related effects occurred more often in our comparison group of amitriptyline overdoses.

Synthesis and structure-activity relationships of N-propyl-N-(4-pyridinyl)-1H-indol-1-amine (besipirdine) and related analogs as potential therapeutic agents for Alzheimer's disease

A series of novel N-(4-pyridinyl)-1H-indol-1-amines and other heteroaryl analogs was synthesized and evaluated in tests to determine potential utility for the treatment of Alzheimer's disease. From these compounds, N-propyl-N-(4-pyridinyl)-1H-indol-1-amine (besipirdine, 4c) was selected for clinical development based on in-depth biological evaluation. In addition to cholinomimetic properties based initially on in vitro inhibition of [3H]quinuclidinyl benzilate binding, in vivo reversal of scopolamine-induced behavioral deficits, and subsequently on other results, 4c also displayed enhancement of adrenergic mechanisms as evidenced in vitro by inhibition of [3H] clonidine binding and synaptosomal biogenic amine uptake, and in vivo by reversal of tetrabenazine-induced ptosis. The synthesis, structure-activity relationships for this series, and the biological profile of 4c are reported.

Five-year multicenter retrospective review of cyclobenzaprine toxicity

Cyclobenzaprine (CBP) has a cyclic structure similar to amitriptyline. In overdose, CBP has been suggested to produce the cardiovascular and neurologic toxicity found with the cyclic antidepressants. To examine this possibility, a retrospective chart review of all cases of CBP exposure reported to five regional poison centers was performed for the years 1989-93. There were a total of 750 charts identified for CBP exposure, of which 523 had data sufficient for evaluation. There were 121 polydrug ingestions leaving 402 pure CBP ingestions. Ages ranged from 7 mo to 77 yrs, with a mean of 20 yrs; 26% were 6 yrs or less. Females comprised 63% of the patient group. No deaths occurred. Dysrhythmias beyond sinus tachycardia were infrequent, and none were life-threatening. No seizures occurred. Common effects were lethargy, sinus tachycardia, and agitation, and both hypertension and hypotension were seen. All symptomatic cases with a known time of ingestion were symptomatic within 4 h of ingestion. Doses ingested ranged from 5-1000 mg, with a mean of 133 mg. Asymptomatic and symptomatic patients had a mean dose ingested of 45 mg and 183 mg, respectively. Treatment was primarily gastrointestinal (GI) decontamination and supportive care. Other therapies required were mechanical ventilation, dopamine, fluid bolus, sedation, and foley catheter. Symptoms requiring treatment beyond GI decontamination did not occur with ingestions less than 100 mg. In conclusion, cyclobenzaprine does not appear to produce the life-threatening cardiovascular or neurologic effects of the cyclic antidepressants in doses less than 1 g. Lethargy and anticholinergic effects are prominent, though serious toxicity is infrequent.

Overdose of cyclobenzaprine, the tricyclic muscle relaxant

A case of cyclobenzaprine (Flexeril) overdose in a 31-year-old woman is presented. The treatment rendered was analogous to treatment protocols implemented for tricyclic overdose. A review of the pharmacology of cyclobenzaprine, as well as the management of patients who overdose on this drug, is presented.

Efforts toward combined analgesic/antidepressants: synthesis and evaluation of (3-aryl-2,3-dihydrobenzofuran-3-yl)alkanamines

Several (3-aryl-2,3-dihydrobenzofuran-3-yl)alkanamines, designed as potential antidepressant agents with analgesic properties, were synthesized and pharmacologically evaluated. While two compounds (1a, 1f) displayed potent antitetrabenazine activity, concomitant antinociceptive activity in the phenylquinone writhing assay was not observed.

Cyclobenzaprine overdosage

The clinical findings in three patients who ingested 260-900 mg cyclobenzaprine (Flexeril) consisted of delayed onset and long duration of anticholinergic symptomatology. In two of these patients, symptoms responded to treatment with physostigmine. The third patient recovered without specific therapy. Despite its structural similarity to amitriptyline, cyclobenzaprine overdosage did not result in coma, seizures, or cardiac toxicity. The pharmacological properties of cyclobenzaprine may account for the observed toxicity.

Chemistry, pharmacology, pharmacokinetics, adverse effects, and efficacy of the antidepressant maprotiline hydrochloride

Maprotiline, a tetracyclic antidepressant with sedative properties, exhibits strong inhibitory effects on norepinephrine uptake across nerve cell membranes but interferes relatively little with serotoninergic mechanisms. The biological half-life of unchanged maprotiline in blood averages 43 hours. Though several studies suggest a more rapid onset of antidepressant effects with maprotiline than with amitriptyline or imipramine, this issue remains unresolved. The adverse effect profile of maprotiline is similar to that of the tricyclic antidepressants, except that rashes are about twice as frequent with maprotiline as with amitriptyline or imipramine. The most frequent adverse reactions are anticholinergic effects and sedation. Data suggest less frequent and severe anticholinergic side effects with maprotiline than with amitriptyline. Maprotiline may be less likely to induce orthostatic hypotension and tachycardia than standard tricyclic antidepressants, but clinically important differences in cardiovascular effects remain to be conclusively demonstrated. Many patients benefit from the convenience of once daily dosing. Maprotiline is comparable in antidepressant efficacy to the tricyclic antidepressants.

Sedative/anxiolytic effects of antidepressants in animals

The sedative effects of several different structural types of antidepressants were investigated in mice. Six different models of sedation were used and the results were averaged. The rank order of sedative potency was: amitriptyline greater than mianserin greater than maprotiline greater than imipramine greater than desipramine greater than clomipramine greater than alaproclate greater than zimelidine greater than norzimelidine. Sedative potency of the antidepressants was found to be significantly correlated with their affinity for four different brain amine receptors. The rank order of correlation of sedation with receptor affinity was: histamine (H1) greater than serotonergic greater than muscarinic greater than alpha 1-adrenergic. These findings appear to be associated with clinical side effects observed during treatment with antidepressants. While scant literature is available concerning specific anxiolytic effects of antidepressants, pharmacological evidence for the role of central 5-HT systems in the anxiolytic effect is plentiful. Our preliminary findings show a marked antagonism of isolation-induced aggression by low doses of the specific 5-HT uptake inhibitor, zimelidine, and the 5-HT releasing agent, p-chloramphetamine, thus supporting the hypothetical importance of 5-HT in the pharmacology of anxiolytic agents.

Antidepressant drugs and ethanol: behavioral and pharmacokinetic interactions in mice

The interactions between ethanol and antidepressant drugs (both tricyclics and newer non-tricyclics) were studied in mice. The ability of these drugs to enhance the sedative effects of ethanol at two different doses (3.2 and 4.0 g/kg) was measured. The percentage of mice losing the righting-reflex was used for the lower dose, and the duration of ethanol-induced sleep was used at the higher dose. The relative order of potency was amitriptyline greater than or equal to imipramine > maprotiline = mianserin > desipramine greater than or equal to chlorimipramine > iprindole greater than or equal to alaproclate > norzimelidine greater than or equal to zimelidine. Amitriptyline (60 mg/kg) caused death in all mice when combined with 4.0 g/kg ethanol. Clinically established antidepressants which enhanced ethanol sedation only at doses considerably above therapeutic levels were zimelidine and iprindole. The relative potency of the antidepressants to enhance ethanol sedation is correlated with their inherent sedative properties which are in turn related to their ability to block central 5-HT, alpha-NA, muscarinic and H1-receptors. Amitriptyline (20 mg/kg) was found to increase ethanol plasma levels to 202, 167 and 132% of control values at 30, 60 and 90 min after ethanol administration, respectively. Desipramine, mianserin and alaproclate also increased ethanol plasma levels initially, but to a lesser extent. These findings suggest that in addition to their sedative effect, several antidepressants, particularly amitriptyline, are likely to interact with ethanol by increasing its concentration in plasma.

The effect of acute and chronic desipramine and amitriptyline treatment on rat brain total 3methoxy-4-hydroxyphenylglycol

The effect of acute (single dose), short-term (4 days), and chronic treatment (21 days) with two tricyclic antidepressants desipramine and amitriptyline on brain 3-methoxy-4-hydroxyphenylglycol (MHPG) was examined in the rat. Amitriptyline had no effect on brain total MHPG irrespective of the duration of the treatment and did not interfere with the lowering effect of clonidine on brain total MHPG. Acute and short-term desipramine treatment decreased brain total MHPG in rats, while chronic desipramine treatment increased it. The differential effect of acute and chronic treatment of desipramine on the brain total MHPG was further demonstrated by the lack of interference with the lowering effect of clonidine on brain total MHPG by one single dose of desipramine; partial interference after 4 days and complete interference after 21 days of desipramine treatment.

Effects of oxypertine on the isolated vas deferens of the rat

1 The isolated vas deferens of the rat was used to examine the peripheral action of oxypertine, a psychotropic-anxiolytic drug. 2 Oxypertine (4.4 X 10(-10) M to 2.6 X 10(-5) M) antagonized competitively the effects of noradrenaline (pA2 = 7.2), 5-hydroxytryptamine (pA2 = 8.6) and dopamine (pA2 = 9.8). 3 Oxypertine (8.8 X 10(-9) M to 2.6 X 10(-5) M) antagonized the effects of low concentrations of acetylcholine and enhanced the contractions elicited by high concentrations of acetylcholine. 4 The contractions evoked by transmural stimulation of the vas deferens were reduced by oxypertine. 5 Oxypertine failed to antagonize the responses to potassium chloride. 6 These findings are compared with the effects of other antidepressant drugs.

Pharmacological studies on tandamine hydrochloride, a potential heterocyclic antidepressant

Tandamine, a potential heterocyclic antidepressant, was compared with imipramine for its ability to modify: (a) the contractions induced by noradrenaline (NA) and 5-hydroxytryptamine (5-HT) on the normal and chronically denervated nictitating membrane of the cat, (b) the neuron blocking effect induced by guanethidine in the guinea pig vas deferens, (c) the electroencephalograph and the physostigmine arousal in the rabbit and (d) the sleep pattern of the rat. Both tandamine and imipramine potentiated the NA and 5-HT induced contractions of the normalnictitating membrane and antagonized the effects of gaunethidine on the vas deferens. The potentiation by tandamine and imipramine of the NA and 5-HT contraction of the nictitating membrane disappeared after chronic denervation of the membrane. These results are consistant with the ability of the substances to block the neural uptake of catechol- and indoleamines. Tandamine did not induce EEG synchronization and did not affect the arousal reaction induced by physostigmine. Tandamine also reduced or abolished REM (rapid eye movement) sleep with a concomitant decrease in NREM (non-rapid eye movement) sleep.

Uptake inhibition of biogenic amines by newer antidepressant drugs: relevance to the dopamine hypothesis of depression

The dopamine theory of depression was studied by assessing the effect of antidepressant drugs on uptake of dopamine, noradrenaline, and serotonin in synaptosomes from rat brain. Five newer drugs--butriptyline, maprotiline, trimipramine, iprindole, and mianserine--exhibited rather potent inhibition of 3H-dopamine uptake in corpus striatum, as their IC50 values, which were in the order of 10(-6)-10(-5) M, were only about 50 times higher than for nomifensine (IC50 = 10(-7) M). The five drugs were weak, compared to chlorimipramine, on 14C-serotonin uptake in the whole forebrain, as their IC50 were about 10(-5) M. Butriptyline, trimipramine, and iprindole were very weak uptake inhibitors of 3H-noradrenaline in the occipital cortex. Their IC50 values were about 10(-6) M, which is almost 1000 times higher than for desmethylimipramine. These results are discussed in relation to comprehensive recent literature as further indicating a link between dopamine and depression.

Effects of tandamine and pirandamine, new potential antidepressants, on the brain uptake of norepinephrine and 5-hydroxytryptamine and related activities

Two novel agents, tandamine (TA; a thiopyrano (3,4-b) indole) and pirandamine (PA; an indeno (2,1-c)pyran), and the tricyclic antidepressants desimipramine (DMI), imipramine (I) and amitriptyline (A) were compared in various in vivo pharmacological tests and for norepinephrine (NE) and 5-hydroxytryptamine (5-HT) neuronal uptake inhibition. TA was found to be equivalent, or greater, in activity to DMI in blocking brain NE uptake, antagonizing reserpine-induced effects and potentiating the behavioural effects of l-Dopa. Similarly to DMI, TA did not appreciably block brain 5-HT uptake; unlike DMI, TA did potentiate central 5-HT activity at high doses. PA exerted an opposite profile to TA, being equivalent to A and greater than I as a 5-HT uptake blocker and central 5-HT potentiator; PA was not effective as a NE uptake blocker or potentiator. Neither TA or PA exhibited in vivo MAO inhibition, and in contrast to DMI, I and A, exhibited no central anticholinergic effects. TA, but not PA, potentiated apomorphine-induced gnawing. These findings indicate that TA is a relatively specific blocker of neuronal NE uptake and PA is a selective 5-HT uptake blocker.