CNS drugs Flashcards

Question

tell me about phenytoin

Answer 1

anti-epileptic and also class Ib anti-arrhythmic agent used in status epilepticus and treatment of arrhythmias e.g. after TCA or digoxin toxicity works via inhibiting VG Na channels. a number of side effects unfortunately * idiosyncratic - gum hyperplasia, hirsutism, acne, SLE, perpheral neuropathy * conc dependant - heart block / hypotension, headaches, confusion, tremor, N&V * teratogenic pharmacokinetics -exhibits 0 order kinetics when just above therapeutic range and therefore needs monitoirng narrow therapeutic index - CYP450 inducer

Answer 2

a mental health illness thought to be due to an imbalance of NT within the brain predominately a deficiency in NA, serotonin or downregulation of their receptors.

Answer 3

depression is thought to be due to reduction in serotonergic, dopamineric and NA pathways within CNS anti-depressants work by targetting these to increase activity. there are 4 main classes of drugs * Selective serotonin reuptake inhibitors (SSRI) - fluoextine and sertraline * serotonin- NA - reuptake inhibitors (SNRIs) - duloxetine and venlafaxine * Tricyclic antidepressants - amitryptilline * Monoamine oxidase inhibitors - phenelzine, moclobimide

Answer 4

selective serotonin reuptake inhibitors block reuptake of serotonin and hence increase serotonin levels in synapse to overcome the deficiency seen in depression include sertraline and fluoextine 1st line in anxiety and depression main side effects include - irritability, GI upset, nausea, anxiety at first. caution for serotonin syndrome, long QTc can get discontinuation syndrome if stopped abruptly - diarrhoea, anxiety, nausea but overall good side effect profile

Answer 5

serotonin - NA - reuptake inhibitors venlafexine, duloxetine have a role in depression and chronic pain block both reuptake - helps increase levels - helps deficiency seen in depression same side effect profile as SSRI but now also HTN due to NA.

Answer 6

tricyclic antidressants include amitripyltipine often used in chronic neuropathic pain. their use in depression mostly been replaced with newer safer agents. they block reuptake of NA and 5HT3 also anti-muscarnic, antihistaminic and anti a1 adrenerfic worse side effect profile as less specific - reduce seizure threshold - anticholinergic symptoms - dry mouth, tachycardia, blured vision, constipation - prolonged QTc

Answer 7

TCA have a narrow therapeutic window and are toxic in overdose in particular they prolong QTc and reduce seizure threshold. Overdose should be managed with A to E approach manage seizures alkalinisation of blood improves protein binding - sodium bicarb if metabolic acidosis

Answer 8

continue as normal be aware can increase MAC avoid drugs that promote NA release - ketamine, ephedrine

Answer 9

symptoms of anti-cholinergic and sympathetic e.g. dry mouth, constipation, tachycardia, blurred vision long QTc metabolic acidosis seizures

Answer 10

monoamine oxidase is an enzyme responsible for the breakdown of NA and serotonin (MAO-A) it is located on mitochondrial membrane by inhibiting this enzyme, levels of NA and 5HT3 can be increased to help treat depression. also used in OCD and chronic pain, migraines. e.g. moclobimide and phenelzine rarely used due to interactions with tyramine containing foods (cheese, chocolate) and side effect profile e.g. HTN crisis other side effects include weight gain and erectile dysfunction. also risk of serotonin syndrome.

Answer 11

anything increasing NA/ 5HT3 ephedrine, ketamine, amphetamines, cocaine, tramadol, pethidine, TCA risk of HTN crisis and serotonin crisis

Answer 12

a lot work by increasing NA and serotonin therefore any anaesthetic agents doing similar will put them at risk of serotonin syndrome or HTN crisis e.g. pethidine and tramadol - increase NA and 5HT3 ephedrine - increases NA ketamine - activates sympathetic NS hence NA pancuronium - also increases NA

Answer 13

Adverse drug reaction which is potentially life threatening due to increased levels of 5HT3 features include - CNS: agitation, confusion, seizures MSK: rigitdity, hyperreflexia and clonus, rhabdomyolyiss CVS : tachycardia, hypotenison autonomic - dilated pupils, hyperthermia, sweating caused by 2 or more serotonergic drugs e.g. SSRI, SNRIs, cocaine, MDMA

Answer 14

group 1 metal from period table used for depression, bipolar works via mimicking Na hence reduces excitability unfortunately has a narrow therapeutic index with many side effects and thus needs monitoring. common - tremor, D+V, weight gain less common - seizures, haemolysis, bradycardia / AV block. nephrogenic diabetes insipidus (antagonises ADH), hypothyroidism. in terms of anaesthesia - reduces MAC and prolongs NMBA

Answer 15

serotonin syndrome - from too much 5HT3 neuroleptic malginant syndrome - from dopamine receptor blockade hence assocaited with anti-psychotics both cause - hyperthermia, muscle rigidity, altered mental state. however serotonin is acute in onset causes hyperflexia and tremor. dilated pupils. NMS is more gradual and causes hyporeflexia and led pipe rigidity. pupils are not usually dilated

Answer 16

thought to be due to too much dopamine hence work via D2 receptor antagonism e.g. schizophrenia and delirium 2 groups first gen = typical = haloperidol, chlorpromazine second gen = atypical = clozapine, rispiridone, quietiapine

Answer 17

D2 antagonism can result in extrapyramidol effects - more common with first generation = tremor, bradykinesia, rigidity, akinesia, occulogyric crisis , tarditive dyskinesia also results in more prolactin (as normally dopamine inhibits prolactin) - hence galactorrhoea and infertility clozapine - important side effect = agranulocytosis atypicals commonly cause weight gain

Answer 18

types of extrapyramidal side effects occulogyric crisis = acute involuntary dystonia of eyes - fixed upwards gaze. may also have other dystonias e.g. torticolis cuased by anti-psychotics or acute withdrawal or dopamine agonists used in parkinsons can be treated with anti-cholinergics e.g. procyclidine