Week 10 Gastrointestinal pharmacology and local and general anaethesia


Flashcards on Week 10 Gastrointestinal pharmacology and local and general anaethesia, created by Elizabeth Then on 15/10/2017.
Elizabeth Then
Flashcards by Elizabeth Then, updated more than 1 year ago
Elizabeth Then
Created by Elizabeth Then about 6 years ago

Resource summary

Question Answer
HCL secretion secreted by parietal cells in the stomach
Drugs which reduce acid antacids H2 receptor antagonists Proton pump inhibitors
Antacids alkali to neutralise effect of acid good for short term management of minor symptoms not useful for ulcer healing
Antacids adverse effects constipation, diarrhoea
H2 receptor antagonists mechanism of action Block H2 receptor, 90% reduction in HCL secretion, e.g. ranitidine
H2 receptor antagonist adverse effects very few, and well tolerated
Proton pump inhibitors mechanism of action blocks acid secretion via proton pump e.g. omeprazole, pantoprazole
Proton pump inhibitor adverse effects inhibit P450, drug interactions, long term: increase risk of pneumonia and osteoporosis, B12 malabsorption
HCL secretion stimulated by Gastrin, histamine, acetylcholine
Gastrin mechanism of action acts on receptors to cause release of histamine and parietal cell influx of Ca to increase HCL
Ach mechanism of action acts on muscarinic receptors and parietal cells to increase HCL secretion
Histamine mechanism of action acts on H2 receptors on parietal cells to increase HCL secretion
Vomiting nausea CTZ Chemoreceptor trigger zone, vomiting centre, outside blood-brain barrier
Drugs used to treat vomiting and nausea: D2 receptor antagonist (dopamine) Mechanism of action: acts in CTZ to prevent vomiting reflex, peripherally increase gut motility e.g. metoclopramide
D2 receptor antagonist adverse effects blocks CNS receptors, fatigue, motor restlessness
Drugs used to treat nausea and vomiting: Histamine (H1) antagonists mechanism of action: blocks H1 receptors in vomiting centre e.g. promethazine
H1 receptor antagonist adverse effects Blocks CNS receptors, fatigue, dry mouth, constipation
Drugs used to treat vomiting and nausea: 5HT3 antagonists Mechanism of action: particularly effective for prevention and treatment of post-operative and chemotherapy induced vomiting. e.g. ondansetron, tropisetron
5HT3 antagonists adverse effects constipation, diarrhea, headache
Drugs that target the GIT Gastric secretion: HCL and pepsinogen secretion Vomiting (nausea): in response to ingestion of toxic substances, unwanted side effects
Local anaesthesia reversible loss of sensation in a localised area
General anesthesia loss of sensation and loss and consciousness
Local anaesthesia desirable properties: sufficient duration of action low systemic toxicity at effective concentrations quick onset reversible
LA mechanism of action: blocks NA channels, halts nerve action potentials, small fibres first, large fibres last. reverse order for recovery.
2 types of LA properties ester: cocaine, procaine, short duration of action Amide: lignocaine, bupivacaine, long duration of action ester= reactive metabolite= allergy and hypersensitivity
Administration of LA routes topical, infiltration, nerve block, spinal, epidural, different onset and duration of action
LA duration of action increase with vasoconstrictor (e.g. adrenaline), increase due to contact with nerve, decrease rate of absorption
LA adverse effects cardiovascular, hypersensitivity, CNS (seizures/coma), treat acute toxicity by giving respiratory assistance, drugs to control seizures (diazepam) drugs to control hypotension (adrenaline)
General anaesthetics desirable properties: analgesia amnesia loss of consciousness inhibition of sensory and autonomic reflexes
GA desirable properties use combination of drugs to achieve balanced anaesthesia
4 stages of anaesthesia 1. analgesia= conscious but not drowsy, without amnesia 2. delirium= amnesic, irregular respiration 3. surgical anaesthesia = re-establishment of regular breathing 4. medullary paralysis = severe depression of medulla, require circulatory and respiratory support
GA mechanism of action nerve block, increase inhibitory and excitatory neurotransmitters
Inhalational GA agents mechanism of action PK uptake and distribution from lungs to blood to CNS: depends on solubility, conc in inspired air, ventilation rate, and pulmonary blood flow
Types of inhalational agents GA Gaseous: nitrous oxide volatile liquid: halothane, enflurane, isoflurane
GA: inhalation agents: solubility indicators lipid solubility: determines potency aqueous solubility: determines rate of induction and recovery
Inhalation agents provide controlled anaesthesia
Nitrous oxide advantages/disadvantages advantages: non-flammable, rapid induction, no muscle relaxant activity disadvantages: low potency, no surgical anaesthesia, can cause decrease in RBC
Halothane advantages and disadvantages moderately potent disadvantages: little analgesia and muscle relaxation, resp depression, hypotension, hypoxemia
Enflurane advantages and disadvantages fast induction and recovery Disadvantages: may cause seizures, potential renal toxicity
Intravenous (IV) agents GA: induce anaesthesia, hypnosis, analgesia, muscle relaxation, control of autonomic reflexes
IV agents GA: advantages/disadvantages advantages: rapid onset, short duration, no resp irritation Disadvantages: inability controlling depth, severe resp and cardiovascular depression
Other agents GA used in combination muscarinic receptor antagonist: mechanism of action: limit bronchial and salivary secretion e.g. atropine
Other agents: neuromuscular blockers mechanism of action prevent reflex movement and paralysis of skeletal muscles e.g.suxamethonium
Other agents: anxiolytics mechanism of action decrease anxiety e.g. diazepam
Other agents: opioids mechanism of action analgesia, sedation e.g. morphine
Other agents antipsychotics mechanism of action decrease vomiting, cause sedation e.g. droperidol
GA overall goal balanced anaesthesia induction (IV) maintenance (inhalation) muscle relaxation analgesia
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