VIVA VOCE: DRUGS Flashcards
Adrenaline
A naturally occurring catecholamine which acts on α1- & ß1/2-adrenergic receptors.
- α1: vasoconstriction, increases vascular permeability (which can cause the loss of intravascular fluid volume & hypotension), reduces oropharyngeal angioedema.
- ß1: increase HR (chronotropy), increase myocardial contraction (inotropy), increase ventricular irritability, vasoconstriction in skin & mucosa.
- ß2: smooth muscle relaxant (bronchodilation), inhibits inflammatory mediator release.
Adrenaline binds to specific receptors on immune cells which helps to suppress histamine release (responsible for allergic reactions). It also produces an increase in blood sugar & glycogenolysis in the liver.
- Side effects: anxiety, hypertension, palpitations, pupil dilation, tremor.
Aspirin
An antiplatelet drug which blocks prostaglandin synthesis. It inhibits platelet aggregation by irreversibly inhibiting cycloxygenase (COX), reducing synthesis of thromboxane A2. This action prevents platelets from aggregating to exposed collagen fibres at the site of vascular injury.
- Side effects: epigastric pain, nausea/vomiting, gastritis, GI bleeding, NSAID-induced bronchospasm
Fentanyl & Morphine
Mu (opioid) receptor agonists which reduce GABAergic neurotransmission & increase parasympathetic activity. GABA release –> hypopolarisation –> CNS depression, activation of dopaminergic pathways in CNS –> change perception/disassociation from pain + euphoria. The inhibition of nociceptive afferent neurons in the PNS impairs transmission of pain messages.
- Side effects: (Boy Does He Need Pain Relief) bradycardic, drowsy, hypotensive, nausea, pinpoint pupils, respiratory depression.
GTN
In small doses, GTN relaxes vascular smooth muscles, causing arteriolar & vasodilatation. High doses increase blood flow to the myocardium, reduce cardiac pre-load, myocardial wall stress, coronary artery spasm, vascular resistance, & BP.
- Side effects: dizziness, hypotension, syncope, reflex tachycardia, vascular headaches.
Hydrocortisone
An adrenocorticoid which binds to glucocorticoid receptors, inhibiting phospholipase A2, promoting anti-inflammatory activity. It has immunosuppressive properties & anti-proliferative actions.
- Side effects: nil.
Ibuprofen
NSAIDs decrease inflammation & reduce fluid accumulation. Ibuprofen inhibits the synthesis of prostaglandins, reducing the inflammatory response. It interferes with the action of cyclooxygenase (an enzyme that catalyses the conversion of arachidonic acid –> prostaglandic acid).
Ipratropium bromide
An anticholinergic which blocks action on muscarinic receptors, promoting bronchodilation & reducing mucus production. The airways’ diameter is controlled by releasing acetylcholine (ACh) into the muscle cells, causing them to contract & narrow the airway. Ipratropium inhibits the activity of ACh in the smooth muscle preventing the contraction –> dilated airways. It is localised to the resp. system as it’s a charged ion.
- Side effects: dilated pupils, dry mouth, palpitations.
Methoxyflurane
A general INH anaesthetic which induces muscle relaxation & reduces pain sensitivity by altering tissue excitability. It decreases the extent of gap junction-mediated cell-cell coupling & alters the activity of the channels that underlie the action potential.
- Side effects: ALOC, cough, renal/hepatic failure.
Midazolam
A short-acting benzodiazepine which induces depressive CNS effects (e.g. muscle relaxation, amnesia, anaesthesia, hypnosis, sedation, hypotension). It achieves this by enhancing the action of the inhibitory neurotransmitter GABA. GABA attaches to receptors to facilitate an influx of Cl- ions which cause cell membrane hyperpolarisation, decreasing the possibility for an action potential.
- Side effects: hypotension, resp. depression (particularly when taken with other CNS depressants, including alcohol & narcotics).
Ondansetron
A serotonin receptor antagonist which blocks the action of serotonin. Serotonin stimulates vagal & splanchnic nerve receptors that project to the medullary vomiting centre & 5-HT3 receptors in the postrema, initiating the vomiting reflex, causing nausea & vomiting.
- Side effects: headache, constipation.
Oxygen
Increases the arterial pressure of O2, improving gas exchange & O2 delivery to tissues. O2 is an electron acceptor during oxidative phosphorylation via the citric acid cycle, achieving aerobic respiration to produce ATP. O2 supplementation restores normal cell activity at the mitochondrial level, reducing metabolic acidosis.
- Side effects: hypoventilation (in COPD Pt’s. with hypoxic drive), drying of airway mucous membranes.
Paracetamol
It inhibits COX, which blocks the production of prostaglandins (responsible for eliciting pain sensations). Paracetamol does not inhibit COX in peripheral tissues & has no peripheral anti-inflammatory effects, unlike NSAIDs. The antipyretic actions are attributed to direct action on the hypothalamus, resulting in peripheral vasodilation, sweating, & loss of body heat.
- Side effects: nausea.
Salbutamol
A ß2-adrenergic agonist which relaxes the smooth muscles of the airway, causing bronchodilation, reducing wheeze & hyperinflation/air trapping.
- Side effects: anxiety, tachyarrhythmias, tremor, hypokalaemia & metabolic acidosis.
