{"id":424,"date":"2020-02-16T11:25:43","date_gmt":"2020-02-16T05:55:43","guid":{"rendered":"https:\/\/medicineplexus.com\/?p=424"},"modified":"2020-02-16T11:25:43","modified_gmt":"2020-02-16T05:55:43","slug":"evaluation-of-antidepressant-drugs","status":"publish","type":"post","link":"https:\/\/medicineplexus.com\/evaluation-of-antidepressant-drugs\/","title":{"rendered":"Evaluation of antidepressant drugs"},"content":{"rendered":"\n

Evaluation of antidepressant drugs<\/u><\/em><\/strong><\/p>\n\n\n\n

Need for new drugs:<\/strong><\/p>\n\n\n\n

  1. High suicide rates in severe depression even if pharmacotherapy is available.
    1. 1\/3rd<\/sup> patients are resistant.<\/li><\/ol>
      1. Some patients show low compliance. All presently available class of drugs are a\/w numerous s\/e.<\/li><\/ol><\/li><\/ol>\n\n\n\n

        In-vitro assay.<\/strong><\/p>\n\n\n\n

        Receptor binding assay<\/strong>:<\/p>\n\n\n\n

        • Isolate the appropriate cells with receptors of interest.<\/li>
        • Add radioactive ligand in the presence and absence of the test drug.<\/li>
        • Count the receptor ligand binding by liquid scintillography.<\/li>
        • The test drug displaces the known ligand from the receptor.<\/li>
        • Alpha adrenoceptor assay:<\/strong> rat cortex, 3H-Yohimbine<\/strong><\/li>
        • Muscarnic receptor assay:<\/strong> Rat cerebellum, 3H-Quinuclidinyl benzilate (QNB)<\/strong><\/li>
        • Monoamine oxidase inhibition<\/strong>: Inhibition of type A and type B monoamine oxidase activities in rat brain synaptosomes<\/li><\/ul>\n\n\n\n

          Measurement of beta-adrenoceptor stimulated adenylate cyclase<\/strong>:<\/p>\n\n\n\n

          • Take male SD rats and treat them with desipramine<\/strong> or vehicle for 14 days.<\/li>
          • Isolate the brains and take slices.<\/li>
          • Add 3H-adenine<\/strong> and incubate with buffer and NA.<\/li>
          • Take the supernatant and count for radioactivity.<\/li>
          • The activity of adenylate cyclase is calculated as the conversion of [3H]-adenine to [3H]-cyclic AMP.<\/strong><\/li>
          • After treatment with antidepressants, this conversion rate is not altered without stimulation by noradrenaline, but significantly reduced in slices treated with the maximally stimulating concentration of 100 \u00b5M noradrenaline.<\/li><\/ul>\n\n\n\n

            Assays for determining decreased uptake of the amines<\/strong>: (Norepinephrine\/Dopamine\/Serotonin)<\/strong><\/p>\n\n\n\n

            • Isolate the hypothalamus or corpora striata and homogenize it with sucrose solution.<\/li>
            • Centrifuge and take the supernatant.<\/li>
            • Add 3H-NE or 3H-DA or 3H-5HT to the supernatant, add a buffer and centrifuge again after adding test drug or control.<\/li>
            • Aspirate the supernatant and measure the monoamine by liquid scintillography.<\/li>
            • Compare IC50 b\/w test and control.<\/li><\/ul>\n\n\n\n
              • Additional assays<\/strong>: Binding to monoamine transporters. Monoamine oxidase inhibition assays<\/li>
              • Information that we get after in-vitro assays:<\/strong> Which receptors do the drug attaches to. Class of the drug. Possible s\/e to look for in animal in-vivo experiments.<\/li><\/ul>\n\n\n\n

                In Vivo<\/strong><\/p>\n\n\n\n

                1. Gross behavior test.<\/p>\n\n\n\n

                2. Test based on inhibition of amine uptake.<\/p>\n\n\n\n

                3. Test Based on anticholinergic activity.<\/p>\n\n\n\n

                4. Test based on depletion of biogenic amine.<\/p>\n\n\n\n

                5. Hypermotility in olfactory-bulbectomized rats<\/p>\n\n\n\n

                • Gross behavioral models.<\/strong><\/li><\/ul>\n\n\n\n

                  Forced swimming test.<\/strong><\/p>\n\n\n\n

                  • Animals: Wistar rats of  either sex weighing  200-225 gms.<\/li>
                  • Plexiglas cylinder (h= 40 c.m., d=18 c.m. containing 15 c.m. of water)<\/li>
                  • Duration of treatment<\/li>
                  • Acute: 1 days<\/li>
                  • Chronic: 13 days<\/li><\/ul>\n\n\n\n

                    Final Observation <\/em><\/strong>\u00e0 Immobility time during 6 mins (360 seconds)<\/em><\/strong><\/p>\n\n\n\n

                    Adv<\/strong>: Relative simplicity<\/p>\n\n\n\n

                    • Sensitive to a large number of atypical antidepressants otherwise inactive in the more classical tests.<\/li><\/ul>\n\n\n\n

                      Limitation<\/strong><\/p>\n\n\n\n

                      • Stimulants like amphetamine and caffeine, also reduce duration of immobility.<\/li>
                      • Differentiation is done by measurement of locomotor Activity by open field test.<\/li><\/ul>\n\n\n\n

                        Tail suspension test in mice<\/strong><\/p>\n\n\n\n

                        • The immobility displayed by rodents when subjected to an unavoidable and inescapable stress reflect behavioral despair.<\/li>
                        • mice ( 20\u201325 g) \u00e0Test drug is given i.p. 30 minutes prior to testing.<\/li>
                        • The mice are suspended on the edge of a shelf above a table top by adhesive tape placed approximately 1 cm from the tip of the tail. The duration of immobility is recorded for a period of 5 min.<\/strong><\/li>
                        • EVALUATION<\/strong><\/li>
                        • The percentage of animals showing the passive behavior is counted and compared with vehicle treated controls.<\/li>
                        • Using various doses, ED50 values can be calculated.<\/li><\/ul>\n\n\n\n

                          Disadv: Several mouse strains are inherently resistant to TST.<\/p>\n\n\n\n

                          Learned helplessness model.<\/strong><\/p>\n\n\n\n

                          • Animals exposed to inescapable and unavoidable electric shocks in one situation later fail to escape shock in a different situation when escape is possible.<\/li>
                          • Male SD rats (300 g)<\/li>
                          • Apparatus – Box with a grid floor having a platform which can be inserted through one side wall to allow a jump-up escape response.<\/li>
                          • Training – Exposure to electric shock (0.7 mA) for 1 h on a schedule of 10 s of shock\/min.<\/strong><\/li>
                          • The platform is not available during training.<\/li>
                          • This training resulted in 80% acquiring learned helplessness behavior.<\/li>
                          • Shock is given without escape chance for 1 hour.<\/li>
                          • Then platform is provided as a route of escape.<\/li>
                          • Antidepressants increase the escaping behavior as compared to controls.<\/li>
                          • EVALUATION<\/strong><\/li>
                          • A drug is considered to be effective, if the learned helplessness is reduced and the number of failures to escape is decreased.<\/strong><\/li><\/ul>\n\n\n\n

                            Muricide behavior in rats<\/strong><\/p>\n\n\n\n

                            • Male Sprague-Dawley rats <\/li>
                            • Only rats consistently killing mice within 5 min after presentation are used for the test.<\/li>
                            • Drugs are injected i.p. to the rats before the test. Mice are presented 30, 60 and 120 min after drug administration.<\/li>
                            • EVALUATION<\/strong><\/li>
                            • Failure to kill a mouse within 5 min is considered inhibition of muricidal behavior.<\/li>
                            • ED50 is calculated, the ED50 is defined as the dose which inhibits mouse killing in 50% of the rats.<\/li>
                            • The mouse-killing behavior is also inhibited d-amphetamine some antihistamines  and some cholinergic drugs.<\/li>
                            • Other models: catalepsy antagonism in chicken<\/li><\/ul>\n\n\n\n

                              Tests based on inhibition of amine reuptake<\/strong><\/p>\n\n\n\n

                              Potentiation of NE toxicity in mice:<\/strong><\/p>\n\n\n\n

                              • sublethal doses are given to mice of 3 mg\/kg noradrenaline.<\/li>
                              • This is followed by administration of the test drug.<\/li>
                              • The mortality rate is assessed 48 h post-dosing. ED<\/em>50 is calculated.<\/li>
                              • Test drugs which increase mortality can be thought to decrease NE reuptake<\/strong><\/li><\/ul>\n\n\n\n

                                Potentiation of 5HTP (5 hydroxy tryptophan) in mice:<\/strong><\/p>\n\n\n\n

                                • Test drug is given at 0 mins.<\/li>
                                • This is followed 30 min later by Pargyline which inhibits MAO.<\/li>
                                • At 120 mins 5HTP is given.<\/li>
                                • 5HTP is converted to serotonin.<\/li>
                                • If test drug decreases serotonin reuptake then mice show characteristic head twitches.<\/strong><\/li>
                                • If the test drug inhibits MAO then the head twitches are seen even without administration of pargyline.<\/li><\/ul>\n\n\n\n

                                  Potentiation of 5HTP (5 hydroxy tryptophan) in rats.<\/strong><\/p>\n\n\n\n

                                  • In contrast to mice exhibiting head twitches, rats show continuous forelimb clonus<\/strong><\/li><\/ul>\n\n\n\n
                                    • Test based on anticholinergic activity<\/strong><\/li><\/ul>\n\n\n\n

                                      Compulsive gnawing in mice<\/strong>.<\/p>\n\n\n\n

                                      •  Treatment of rodents with apomorphine<\/strong> causes compulsive gnawing instead of vomiting due to dopaminergic stimulation.<\/li>
                                      • Anticholinergics<\/strong> shift the balance between Ach & dopamine resulting in an enhancement of apomorphine effect.<\/strong><\/li>
                                      • Ach \u00e0 increase gnawing<\/li>
                                      • Mice are injected s.c. with 10 mg\/kg apomorphine + test drug\/vehicle at the same time.<\/li>
                                      • Immediately, mice are placed in a cage with corrugated paper the corrugation facing upwards for 1 hour.<\/strong><\/li>
                                      • The mice start to bite into the paper causing fine holes or tear the paper.<\/li>
                                      • The template having 10 rectangle windows divided into 10 areas of the same size are placed over the corrugated paper.<\/li>
                                      • In a total of 100 areas number of bites is checked.<\/li>
                                      • Percentage of damaged paper in calculated.<\/strong><\/li>
                                      • This behavior is enhanced by antidepressants.<\/strong><\/li>
                                      • Not only antidepressants, but also centrally acting anticholinergics and antihistaminics are active in this test.<\/li><\/ul>\n\n\n\n

                                        Tests based on depletion of monoamines<\/strong><\/p>\n\n\n\n

                                        • Tetrabenazine antagonism in mice<\/strong><\/strong><\/li>
                                        • Tetrabenazine (TBZ) induces a depletion of biogenic amines (e.g. noradrenaline, dopamine, serotonin) without affecting their de novo synthesis.<\/li>
                                        • Catalepsy and ptosis<\/strong> are used as criteria.<\/li>
                                        • Antidepressants antagonize  the effect of TBZ<\/li><\/ul>\n\n\n\n
                                          • Reserpine induced hypothermia in mice.<\/strong>
                                            • Depletion of biogenic amines (noradrenaline, 5-hydroxytryptamine, dopamine) in the brain also induces hypothermia in rodents.<\/li><\/ul>
                                              • The decrease of body temperature induced by reserpine is antagonized by antidepressants.<\/li><\/ul>
                                                • Rectal temperature is recorded every hour.<\/li><\/ul>
                                                  • The difference in temperature from vehicle controls is calculated for each time and the maximal difference is scored.<\/li><\/ul>
                                                    • The differences are then statistically compared using the t-test.<\/li><\/ul>
                                                      • The reversal of hypothermia is not specific for antidepressants. The fall in body temperature can also be antagonized by amphetamines, and some antipsychotic agents (chlorpromazine).<\/li><\/ul><\/li><\/ul>\n\n\n\n
                                                        • Hypermotility in olfactory bulbectomized rats:<\/strong>
                                                          • Bilateral olfactory bulbectomy in the rat is associated with changes in exploratory behavior that are reversed by chronic, <\/strong>but not acute treatment with antidepressant drugs.<\/strong><\/li><\/ul>
                                                            • The animals are allowed to recover for 14 days after surgery.<\/li><\/ul>
                                                              • the animals are treated s.c. with the test drug \/ standard \/ vehicle once daily for 14 days.<\/strong><\/li><\/ul>
                                                                • The behavior of the animals is tested from the 12th day onwards.<\/strong><\/li><\/ul>
                                                                  • The rats are placed singly in the center of an open field apparatus.<\/strong><\/li><\/ul>
                                                                    • Ambulation (no. of squares crossed), rearing (forepaws raised from the floor), grooming and defecation (no. of fecal boli) scores are recorded for a 3 min period of observation.<\/li><\/ul><\/li><\/ul>\n\n\n\n

                                                                      Other models<\/p>\n\n\n\n

                                                                      • Apomorphine- induced hypothermia in mice.<\/li>
                                                                      • Yohimbine toxicity enhancement.<\/li>
                                                                      • Tryptamine seizure potentiation in rats.<\/li>
                                                                      • Serotonin syndrome in rats.<\/li>
                                                                      • Sexual behavior in male rats.<\/li><\/ul>\n\n\n\n
                                                                        • Clinical evaluation.<\/strong><\/li>
                                                                        • Various scales available for evaluation of depression are: HAM-D (Hamilton depression rating scale), MADRS (Montgomery ASberg Depression rating scale), CGI (Clinical global impression), Becks Depression inventory (BDI).<\/li><\/ul>\n\n\n\n
                                                                          • Phase 1.<\/li>
                                                                          • Objectives: Safety, tolerability, PK and PD.<\/li>
                                                                          • Groups: Young or elderly. Elderly volunteers are more appropriate.<\/li>
                                                                          • Dosing: Single ascending dose study in young. Multiple ascending dose study in elderly.<\/li>
                                                                          • Endpoints: AE, Vital signs, Lab parameters, Physical and neurological examination.<\/li>
                                                                          • PK: Polymorphic hydroxylation<\/li>
                                                                          • PD: Amine pressor test (assessment of peripheral effects of antidepresants), Psychomotor performance (DSST, CFFT), Quantitative EEG.<\/li><\/ul>\n\n\n\n
                                                                            • Phase 2 and 3: Conducted usually for a period of 12 weeks.<\/li>
                                                                            • Objectives: Primary: Compare the efficacy and safety in treatment arm a\/c\/t placebo arm in decreasing symptoms of MDD. Secondary: onset of antidepressant action, duration of antidepressant action and peak of antidepressant action.<\/li>
                                                                            • Inclusion: DSM IV TR. Specific level of MADRS or HAMD. Becks anxiety inventory to exclude comorbid anxiety. No other mental, neurological and medical comorbidities.<\/li>
                                                                            • Endpoints:<\/li>
                                                                            • Primary: change from baseline in MADRS score. Change from Baseline in HAMD score. Snaith Hamilton Pleasure Scale (SHAPS) in which a score of <2 indicates anhedonia. Addiction research center inventory (ARCI ) which measures the reinforcing or dysphoric effects of the test drug. Profile of mood states (POMS) measures drug induced changes in mood.<\/li>
                                                                            • Secondary: Time to onset of a consistent decrease in depressed mood as measured by VAS. Number of patients achieving HAM-D <7. Adverse evens in both the groups.<\/li>
                                                                            • Design: double blind, randomized, placebo-controlled, parallel-group study<\/li><\/ul>\n\n\n\n

                                                                              <\/p>\n","protected":false},"excerpt":{"rendered":"

                                                                              Evaluation of antidepressant drugs Need for new drugs: High suicide rates in severe depression even if pharmacotherapy is available. 1\/3rd patients are resistant. Some patients show low compliance. All presently available class of drugs are a\/w numerous s\/e. In-vitro assay. Receptor binding assay: Isolate the appropriate cells with receptors of interest. Add radioactive ligand in[…]\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","footnotes":""},"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/posts\/424"}],"collection":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/comments?post=424"}],"version-history":[{"count":0,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/posts\/424\/revisions"}],"wp:attachment":[{"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/media?parent=424"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/categories?post=424"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/medicineplexus.com\/wp-json\/wp\/v2\/tags?post=424"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}