Neuro Drugs Flashcards
L-Dopa/Levodopa
This is a structural precursor for dopamine, adrenaline and noradrenaline (THE CATECHOLAMINES). Unlike the NTs themselves it is able to cross the BBB where it is converted into an active form of dopamine to increase brain concentration. Very useful for the treatment of Parkinson's Disease where neurones the substantial nigra become de-pigmented and mix with eosinophils to form LEWY BODIES hence stopping the substantial nigra neurones from releasing dopamine into the corpus striatum. L-Dopa increases dopamine concentrations here and so helps with some of the symptoms of PD. IND: PARKINSON'S DISEASE AE: Some L-dopa is converted to dopamine in the peripheral nervous system hence giving rise to some side effects: - Hypotension - Bradycardia - GI bleeding - Nausea - Disturbed respiration - Hair loss DOSE: 50mg PO QDS (titrate up)
Phenytoin
ANTI-CONVULSANT. Inhibits Na+ channels on neurones hence helping them resist depolarisation and the spread of disordered electrical activity in seizures. More in depth knowledge unknown but also seems to have this effect on Purkinje fibres in the heart.
IND: second line for seizures and status epileptics (when bentos have been used first)
Chronic control and reducing frequency of focal and generalised seizures
AE: Can change appearance:
Gum hypertrophy, coarsening of skin, hirsutism, acne
Metabolised by liver so decrease in hepatic impairment and cerebellar toxicity (nystagmus and incoordination)
Do not use in PREGNANCY as there is a chance it can cause craniofacial abnormalities
It is a CYP450 INDUCER and so will decrease the plasma availability of drugs metabolised by this system such as warfarin and oestrogen - it is also itself metabolised by CYP450 and so will be effected by INHIBITORS of this system: amiodarone and diltiazem
DOSE: loading dose 20mg/kg (up to 2g) and then 100mg thereafter
For chronic epilepsy oral dose of 100-300mg
Carbamazepine
Not a great deal known about how it works but thought to work in a similar way to phenytoin: inhibiting Na+ channels to prevent depolarisation of neurones and hence stopping the spread of electrical activity in seizures
IND: First line treatment for the prevention of focal seizures and primary seizures without secondary generalisation
Also useful for TRIGEMINAL NEURALGIA to reduce pain and the frequency of attacks
Also useful for BIPOLAR DISORDER prophylaxis
AE:
Can cause GI upset and near disturbance (ataxia and dizziness)
Hypersensitivity is reasonably common
Can also cause oedema and hyponatraemia
Do not use in pregnancy as it can cause neural tube defects as well as cardiac and urinary tube defects - women wanting to become pregnancy who rely of carbamazepine should take high dose FOLIC ACID before
Do not give in hepatic, renal or cardiac impairment
CYP450 inducer and so will reduce the bioavailability go warfarin and oestrogen. Will be effected by CYP450 inhibitors such as macrocodes (erythromycin, clarithromycin), amiodarone and diltiazem which will increase levels of carbamazepine
Sodium Valproate
Another anti-convulsants that works by inhibiting Na+ channels and hence resisting depolarisation. It ALSO increases the amount of GABA in the brain which is the key DEPRESSANT NT helping to control seizures
IND: it is the FIRST CHOICE for some generalised seizures as well as ABSENCE SEIZURES
Useful for BIPOLAR and treating manic episodes
AE: Gi upset and neuro disturbance (dizziness, ataxia, behavioural changes and tremor)
CYP450 inducer
Do not give in fertile women as can cause fatal abnormalities
Thrombocytopenia
Hypersensitivity leading to hair loss and the hair that grows back being curlier
Can cause liver failure, pancreatitis and death
DOSE: IV and PO 600-750mg
Lamotrigine
ANTI-CONVULSANT: works by inhibiting Na+ channels preventing depolarisation and also increasing GABA. Has good effect
IND: First line for TONIC-CLONIC SEIZURES and some absence seizures (Sodium valproate would normally be used first)
BIPOLAR good for manic episodes (like carbamazepine and sodium valproate) but also good for DEPRESSIVE EPISODES
TRIGEMINAL NEUROPATHY
AE: Ataxia, arthralgia, visual disturbances, Back pain, aggression and anxiety, abdominal pain
DOSE: 25mg 2/52 then 50mg +2/52
Levitaracetam
ANTI-CONVULSANT: HAS NO EFFECT ON SODIUM CHANNELS - works by inhibiting CALCIUM channels on the pre-synaptic neurone hence resisting depolarisation
IND: Add on therapy for epilepsy and seizures
Some effect shown in alzheimer’s disease Tourette’s and anxiety
AE: ataxia, abode pain, aggression, anxiety, cough, depression, drowsiness
HAS NO EFFECT on the use of other anti-convulsants
Can be given in pregnancy but with care
HALF DOSE in hepatic impairment: NOT CONTROLLED BY CYP450 but by other liver enzymes
DOSE: start with 250mg OD and then BD
