11. CNS stimulant. Anticonvulsant drugs Flashcards
Seizures are caused by…
- Abnormal, high-frequency discharge of a group of neurons
- Starting locally → Other parts of the brain
- Progressive
Seizures affect which nervous phenomena?
- Motility
- Sensation
- Behaviour
During a seizure, unconsciousness occurs when…
The reticular formation (group of nuclei) is involved
Seizures are preferred to be treated by…
Monotherapy
Combination therapy during seizures involves…
Any 2 of:
- Phenytoin
- Phenobarbital
- Carbamazepine
Drug treatment of: Status epilepticus
Diazepam
Drug treatment of: Seizures
- Phenobarbital
- Phenytoin
- Valproic acid
Phenobarbital: Summary
Safe, effective & inexpensive barbiturate for chronic therapy in dogs & cats
Phenobarbital: Mechanism of action
- ↑ Activity of GABA (Inhibitory neurotransmitter)
- Opens Cl- channels in excitatory cells
- Neuronal inhibition
- ↓ Neuronal excitotoxicity (via glutamate receptors)
- Inhibition of voltage-gated Ca2+ channels
Phenobarbital: Pharmacokinetics
- Rapidly absorbed after PO
- High bioavailability
- Metabolised primarily in the liver
Phenobarbital: Side effects
- Sedation
- Drowsiness
- Ataxia (loss of body movements)
- Polyphagia
- Polyuria
List the benzodiazepines
- Diazepam
- Carbamazepine
- Midazolam
Diazepam: Clinical uses
- Status epilepticus: Preferred drug
- Premedication & combination (ketamine)
- Muscle relaxation
- Prevention and control of epilepsy
- Sedation
Diazepam: Administration
- Rectal
- IV
Not suitable for PO
Carbamazepine
Similar profile as phenytoin but with fewer unwanted side effects
Phenytoin
Membrane stabilising agent
- Short elimination half-life in dog
- Extremely long in cat (toxicity)
Midazolam
- Shorter effect than diazepam
- Produces less sedation than diazepam
Drugs contraindicated in epileptic patients
- Phenothiazine derivatives:
- Propiopromazine
- Acepromazine
- Chloropromazine
- Butyrophenones:
- Azaperone
CNS stimulants (analeptics) can be categorised into…
- Convulsants & respiratory stimulants
- Psychomotor stimulants
- Psychotomimetic (hallucinogenic) drugs
Convulsants & respiratory stimulants
- Little clinical use → Used in experiments
- Doxapram = Respiratory stimulant in acute resp. failure
- Strychnine, PTZ = Induce convulsions
- PTZ (tests antiepileptic drugs)
Psychomotor stimulants
- Amphetamines
- Cocaine
Amphetamines
- ↑ Motor activity
- Euphoria-excitement
- Anorexia
- Psychotic behaviour after prolonged use
Due to release of catecholamines
Effect for a few hours, followed by depression/anxiety
Amphetamines: Clinical use
- Narcolepsy
- Hyperkinetic children
Cocaine
- Inhibition of catecholamine uptake (esp. dopmine) by nerve terminals
- Shorter duration
- Similar to amphetamines
- Main importance: Abuse
Methylxanthines: Examples
- Caffeine
- Theophylline (bronchodilator)
Methylxanthines: Effect
- ↓ Fatigue
- ↑ Mental performance without euphoria
- CNS stimulation
- Diuresis
- Stimulation of cardiac muscle
- Relaxation of bronchial muscles
Psychotomimetic drugs: Examples
- LSD
- Mescaline
- MDMA
- Phencyclidine
Psychotomimetic drugs: Effects
- Affects thoughts and mood without psychomotor stimulation
- Some can cause acute hyperthermia and death
- 2 main groups
- Drugs acting on 5-Hydroxytryptamine
- Catecholamines
Effect of LSD, Mescaline and MDMA
- Ecstacy: Inhib 5-HT uptake
- MDMA also affects many other receptors
- Psychomimetic effect
- Stimulant effect
- Can cause acute hyperthermia and death
Phencyclidine: Mechanism of action
Blocks glutamate activated NMDA receptors
Barbiturates: Mechanism of action
GABA-BDZ-Barbiturate-Receptor Complex (GABAA)
- ↓ Ca2+ accumulation → inhibition of stimulatory transmitter release → Stimulation of membranes
Barbiturates: Effects (general)
- CNS effect
- Circulatory effect
- Respiratory effect
