allergy and epilepsy drugs Flashcards
why is adrenaline used for anaphylaxis
- alpha 1 antagonist for vasoconstriction
- beta 2 bronchodilation
how does adrenalines work in anaphylaxis
- functional antagonist
- histamine release causes vasodilation and bronchoconstriction
- counters this reaction
what is the mechanism of action of a type 1 (anaphylactic) reaction
- IgE antibodies
- mediated mast cell activation and degranulation
what are histamines
- chemical messenger
- in tissue with large number of mast cells (skin, bronchial tree mucosa, intestinal mucosa)
where is histamine stored
in the granules in the mas cells
how is histamine released
- rise in cytosolic Ca2+ from inflammation and allergic reaction
- IgE binds to mast cells and antigen binds to IgE
- histamine is released via exocytosis
what is the target of histamines for H1 receptors
- bronchial and nasal exocrine glands
- bronchial smooth muscle
- intestinal smooth muscle
- sensory nerve endings
what is the target of histamines for H1 and H2 receptors
- cardiovascular system
- skin
what is the target of histamines for H2 receptors
stomach
what do the bronchial and nasal exocrine glands do when stimulated by H1 receptors
increased production of mucus
what do the bronchial smooth muscles do when stimulated by H1 receptors
contraction of bronchioles
what do the intestinal smooth muscle do when stimulated by H1 receptors
contraction
what do the sensory nerve endings do when stimulated by H1 receptors
itching and pain
what does the cardiovascular system do when stimulated by H1 and H2 receptors
- decreased BP
- positive chronotropism
- positive inotripism
what does the skin do when stimulated by H1 and H2 receptors
triple response: reddening, wheal, flare
what does the stomach do when stimulated by H2 receptors
- stimulation of HCl secretion
how do first generation H1 receptor blockers work
- penetrate the CNS as lipid soluble to cause sedation
- interact with other receptors (unwanted adverse effects)
what do second generation H1 receptor blocking agents do
- specific for H1 receptors
- do not penetrate the blood brain barrier
what are the therapeutic uses for H1 receptor blocking agents
- allergic rhinitis
- allergic conjunctivitis
- urticaria
- nausea
- insomnia
- motion sickness
- increased food intake
- anaphylactic reactions
what are the adverse effects of H1 receptor blocking agents
- central: sedation, dizziness, fatigue
- antimuscarinic: dry mouth, blurred vision, constipation, urine retention
what is status epilepticus
- prolonged state of seizures
- sustained contraction of respiratory muscles
what is the management of status epilepticus
- assess respiratory status
- oxygen
- vital signs
- IV access
- IV benzodiazepine
what is the mechanism of action of benzodiazepines
- increase GABA activity
- this is an inhibitory neurotransmitter in the CNS
- reduces excitability of neurones, calming the brains
how does GABA inhibition have an effect
- GABA
- GABAa opens chloride channels
- allows for a calcium influx
- is an anion so is negatively charged = hyperpolarised cell
- causes inhibition to stop firing
