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Aspirin: acidic or basic? 0- or 1st- order elimination?
Weakly acidic (give bicarbonate), 0-order elimination (PEA)
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Amphetamines: acidic or basic?
Weakly basic
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Loading dose
Target dose * Vd / bioavailability
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Overdose of a weakly basic drug (ex. amphetamines)
Give ammonium chloride, since it's trapped in another acidic environment.
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Phase 1 metabolism
CYP450: redox, hydrolysis. Afterward, the metabolite will be slightly water-soluble & polar. Old people lose Phase I first.
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Phase 2 metabolism
Conjugation to make it more water-soluble for excretion: metabolites are now very polar & inactive. Acetylation, glucuronidation, sulfation.
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Bethanechol
- Activates bowel & bladder smooth muscle -- for ileus (post-op or neurogenic) or urinary retention.
- BethAnne, call me...
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Pilocarpine
Pile on the sweat & tears... and weight (b/c saliva stimulated too).
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Carbachol
Eyes: for glaucoma, pupil contraction, release intraocular pressure
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Methacholine
For asthma dx. A challenge test, b/c this drug stimulates muscarinic receptors in airway.
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The -stigmines
- "Keep, the stale, stagnant one around longer" = parasympathetic. Very stagnant & boring, b/c they don't even work directly... they slow the ACh breakdown enzyme (anti-cholinesterase), so ACh stays around longer to stimulate muscarinic receptors.
- All are good for either m.gravis (where you're losing ACh receptors) or glaucoma.
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Neostigmine
- For: ileus & urinary retention (same as bethanechol), m.gravis, reverse NMJ blockade post-operatively.
- NO CNS penetration.
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Name the muscarinic antagonists useful for: eyes, CNS, respiratory, GU, GI
- Eyes = atropine, tropicamide, homatropine (pupil dilators)
- CNS = benztropine (Parkinson's -- park my Benz), scopolamine (motion sickness)
- Respiratory = ipratropium bromide inhaler
- GU = oxybutynin, glycopyrrolate
- GI = methscopolamine, pirenzepine, propantheline
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Antidote for cholinesterase inhibitor poisoning (ex. neostigmine)
Atropine, an antagonist.
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Epinephrine
Stimulates all 4 (alpha 1&2, beta 1&2)... but at low doses, B1 predominates. Used for glaucoma, anaphylaxis, severe asthma, hypotension.
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Norepinephrine
Alpha-1 and -2 > B1
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Dopamine
All 3: D > B > A. Used for HF and shock (due to dec'd renal perfusion).
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Amphetamine
General sympathetic agonist. Weak base. Used for ADD, narcolepsy, obesity.
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The 4 selective B-2 agonists
- Metaproterenol
- Albuterol
- Salmeterol
- Terbutaline
- (MAST)
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Mirtazapine
Alpha-2-selective antagonist, used for depression. Inc'd serum cholesterol & appetite.
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DHPR Ca++ channel blockers
- More potent than non-DHPR, because the DHPR ones control many RyR channels in sarcoplasmic reticulum.
- Amlodipine, nifedipine.
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Non-DHPR Ca++ channel blockers
Verapamil, diltiazem. Not as potent. Decreased inotropy, so watch for excess bradycardia with Ca++ channel blocker + B-blocker.
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Methanol vs. ethylene glycol: what do they become, & what are the consequences?
- Methanol --> formaldehyde: blindness (retinal damage) + acidosis
- Ethylene glycol --> oxalic acid: toxic to kidneys/acidosis. (Makes sense; salicylic acid is also nephrotoxic.)
Both use alcohol dehydrogenase.
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