13. Random Flashcards
Bronchospasm in asthmatics
Exacerbators
Beta-adrenergic receptor antagonists, aspirin and the non-steroidal anti-inflammatory drugs can exacerbate or provoke an asthma attack.
Salmeterol is a longer acting beta-2 agonist used in the management of asthma, but it may cause paradoxical bronchospasm, which is common with other inhalational drugs.
Captopril can cause a persistent dry cough and bronchospasm has been reported but this is rare.
Paracetamol is safe in asthmatics.
Antidotes
paracetamol
beta blockers
iron poisoning
benzodiazepine
opiate
N-acetylcysteine may be indicated in a paracetamol overdose
Glucagon is given for an overdose of beta blockers
Ethanol is given for methanol poisoning
The antidote for iron poisoning is deferoxamine which chelates iron
Flumazenil is the antidote for benzodiazepine toxicity
Naloxone is the antidote for opiate toxicity.
Medications that need dose adjust in RF
Aciclovir may cause nephrotoxicity by intratubular aciclovir crystalluria and the dose should be reduced in renal failure.
Carbamazepine is approximately 80% protein bound and is metabolised in the liver but is renally excreted. Renal impairment has little effect on the dose, so dose adjustment is not necessary, but the manufacturer does advise caution.
Digoxin and vancomycin both require dose adjustment in patients with renal failure.
In severe renal impairment the dose of erythromycin should be limited to 1.5 g per day because of the risk of ototoxicity.
Nephrotoxicity abx
Nephrotoxicity is associated with many antibiotics typically
Tetracyclines
Cephalosporins and
Gentamicin.
It has also been described in association with
Penicillins (immune origin)
Azetazolamide (carbonic anhydrase inhibitor) and
Rifampicin.
Mydriasis
is what
cause by
Dilatation of the pupil is called mydriasis and is caused by sympathetic stimulation and anticholinergics drugs, for example, hyoscine.
Cocaine has sympathomimetic properties and will cause mydriasis.
Misois is what
cause by
Constriction of the pupil or miosis is caused by parasympathetic stimulation, opioid drugs, for example, morphine, anaesthetic agents and pontine lesions.
Timolol is a beta blocker which causes miosis, and timolol drops are used in the management of glaucoma.
Pulmonary fibrosis is a side effect of the following drugs:
Gold, penicillamine and methotrexate which are used in rheumatology (not nalidixic acid)
Cytotoxic drugs, for example, for example, bleomycin and cyclophosphamide (not vincristine)
Sulphasalazine, amiodarone and nitrofurantoin also cause pulmonary fibrosis.
Unsafe in porphyria
Porphyria is a group of diseases characterised by excess production and excretion of porphyrins and their precursors.
Barbiturates (thiopental and methohexital) Sulphonamides Steroids Alcohol Phenytoin Amiodarone, and the Progestogens are all considered unsafe.
They are caused by enzyme defects within the haem metabolic pathway. Stress, infection, pregnancy, menstruation, starvation and certain drugs may precipitate acute attacks.
Women
Northern Europeans - sweden
Px gi symp px diarr vom
neuro sm - weak convulsi tremor
Deficinecy - porphobilinogen deaminse -
acum heam precursor
Acute porphryia
Hereditary disorders of haem biosynthesis and caution must be exercised when prescribing.
urinary porphobilinogen
Uterotonics
oxytocin
prostaglandins
ergot alkaloids (ergotamine)
Vasopressin - similiar to oxy
His release
from
Causing
inhib
Histamine is released from mast cells following the administration of certain drugs, for example, morphine, d-tubocurare, atracurium.
The release of histamine may cause
Skin erythema and wheals Bronchospasm Hypotension Anaphylaxis, and possibly Cardiac arrest. Loratadine is a H1 receptor antagonist (antihistamine).
Hyoscine is a sedating anticholinergic drug derived from the henbane plant, which only very rarely triggers histamine release.
The mechanisms by which drugs cross the placenta are:
Simple diffusion. Ion channel diffusion Facilitated diffusion Active transport (primary and secondary) Osmosis Exocytosis and Endocytosis
Factors influencing the rate of diffusion across the placenta include:
Materno-foetal concentration gradient. Molecular weight of drug <500 Daltons cross by diffusion Degree of ionisation Maternal and foetal blood pH Thickness of placental membrane Lipid solubility- lipophilic molecules diffuse readily across the placenta Protein binding Placental blood flow
Local anaesthetics & Baby
Local anaesthetics are affected by ion trapping.
The unionised form of the local anaesthetic crosses the placental barrier.
The foetal pH is lower than that of the mother, the unionised form of the local anaesthetic is converted to the ionised form (a weak base made more acidic yields more ionised drug), and the ionised form is trapped in the foetus. T
he more acidotic the foetus, the greater the degree of ion trapping. When foetal pH falls into the range of 7.03-7.23, significant ion trapping occurs. Ion trapping is irrelevant with regard to muscle relaxants.
sodium channel permeability
Carbamazepine
neuronal sodium channels reducing the sodium ion flux until it is insufficient
Suxamethonium is a depolarising neuromuscular blocking drug that inhibits nicotinic acetyl choline receptors. When voltage-sensitive sodium channels sense membrane depolarization (as a result of activation of the ACh receptors), they initially open and thereafter close and become inactivated.
Anticholinergic drugs
Act @ Muscarinic receptors - Acetylcholine is an agonist.
Atropine, glycopyrrolate and hyoscine.
bronchodilation.
Both atropine and hyoscine are tertiary amines and have the potential to cross the placenta and blood-brain barrier (BBB) to produce central effects.
Hyoscine has the potential to produce amnesia.
Glycopyrrolate is a quaternary amine and cannot cross the placenta and the BBB.
Anticholinergic agents may decrease the tone of the lower oesophageal sphincter
