Modules 12-17 - Mechanisms, Adverse effects and important considerations Flashcards
Statins:
Mechanism of action including overall therapeutic benefit
Main difference between the two statins.
Adverse effects
Inhibit HMG-CoA reductase.
Increases hepatic LDL receptors.
Decreases plasma LDL
1) increase HDL
2) Decrease LDL
3) Decrease TGs
Atorvastatin (Lipitor) vs. Rosuvastatin (Crestor)
Rosuvastatin is not greatly metabolized and caution must be exercised when prescribing to Asian patients
Adverse effects: Myopathy Hepatotoxicity Rhabdomyolysis (can lead to cardiac dysrhythmias) Teratogenic
Nicotinic Acid/Niacin Vitamin name? Mechanism of action Therapeutic benefit Adverse effects
Vitamin B3
Inhibits hepatic VLDL secretion –> less LDL in plasma as a result
Increased HDL + decreased LDL
Skin rash, Hepatotoxicity, hyperglycemia, Facial flushing, Increased levels of uric acid
Bile acid sequestrants
Mechanism of action
Adverse effects
Positively charged molecules that bind to bile acids (negatively charged) and prevent intestinal absorption of bile acids.
This causes a need for cholesterol for bile acid synthesis. Thus, there are increased hepatic LDL receptors, and less plasma LDL
Bloating, Constipation, Decreased absorption (thiazide diuretics, certain antibiotics, warfarin, digoxin)
Cholesterol absorption inhibitors
Combination pill
Mechanism of action
Adverse effects
Combination pill - statin + cholesterol absorption inhibitor - called vytorin [simvastatin + ezetimibe (Zetia)]
Binds to and inhibits intestinal cholesterol transporter, NPC1L1. This decreases cholesterol absorption –> decreased plasma LDL + increased hepatic cholesterol synthesis
No major adverse effects
Often used in combination with statins
Fibrates
Mechanism of action
Overall therapeutic benefit
Adverse effects
Activates PPAR-alpha:
1) Increased lipoprotein lipase synthesis
2) Decreased apolipoprotein CIII (lipoprotein lipase inhibitor)
3) Increased apolipoprotein a1, a2 (transport of lipids to the liver)
Decreased TGs and increased HDL
Increased risk of gallstones, myopathy, hepatotoxicity
Pathogenesis of atherosclerosis
Endothelial cell injury (smoking, hemodynamic factors, immune reaction, elevated blood lipids, HTN)
LDL cholesterol invades the sub-endothelial space
LDL becomes oxidized, and recruits monocytes
Monocytes become macrophages and engulf the oxidized LDL
Macrophages enlarge and become vacuolated = Foam cells
As foam cells accumulate, a fatty streak appears
As the fatty streak grows, platelet adhesion, smooth muscle migration and collagen synthesis occurs –> fibrous cap
Primary treatment of high LDL cholesterol/atherosclerosis.
Lifestyle modifications:
- Smoking reduction
- Exercise
- Weight control/diet
Loop Diuretics
Mechanism of Action
Adverse effects
Usual indication
Work at the ascending Loop of Henle to reduce Na+/Cl- reabsorption (with the unfortunate side effect of causing reduced potassium reabsorption)
This promotes sodium-chloride, and thus water excretion, decreasing BP (through a decrease in blood volume)
Adverse effects: Hypokalemia, Hyponatremia, Hypotension, Dehydration
Used in severe fluid overload cases - i.e. edema, severe renal failure, severe HTN (not responding to other diuretics)
Thiazide diuretics
Mechanism of action
Adverse effects\
Blocks Na+/Cl- reabsorption in the distal tubule –> decreased water reasborption –> decreased BP
Adverse effects: Hyponetremia, Hypokalemia, Dehydration
Potassium sparing diuretics/Aldosterone antagonists
Mechanism of action
Adverse effects
Important contraindication
Inhibit aldosterone receptors in the collecting duct –> decreased sodium reabsorption = decreased potassium excretion –> water excretion –> decreased BP
Adverse effects: hyperkalemia
DO NOT use with ACEIs or ARBs
Beta Blockers
Mechanism of Action - differentiate between 1st and 2nd generation
Adverse effects
Suffix
Block beta 1 receptors in the heart (Decreased CO and BP) and in the juxtaglomerular cells (decreased renin production = decreased PVR).
1st generation beta blockers also block beta 2 receptors in the lungs
Adverse effects: 2nd generation (selective): Bradycardia, rebound HTN, cardiac failure (rare), decreased CO 1st generation (non-selective) - additional AEs include bronchoconstriction and inhibition of glycogenolysis
“olol” - e.g. metaprolol
ACEIs
Mechanism of action
Adverse effects
Suffix
Inhibit ACE in the lungs –> reduction of angiotensin II production –> reduction of aldosterone (decreased Na+ reasborption), ADH (decreased water reabsorption) and decreased PVR (angiotensin II no longer binds to AT1 on smooth muscle)
Inhibition of bradykin breakdown (vasodilation)
Overall: decreased blood volume = decreased CO, and decreased PVR
Adverse effects:
-Angiotensin II: 1st dose hypotension, hyperkalemia (DO NOT USE WITH POTASSIUM SPARING DIURETICS)
Bradykinin: Persistent cough, angioedema
Suffix: “ipril” - e.g. Ramipril
ARBs Mechanism of action Therapeutic benefit Adverse effects suffix
Block the angiotensin II receptor (AT1) on smooth muscle (decreased PVR), and inhibit aldosterone synthesis (decreased Na+/H20 reabsorption)
Decreased blood volume (decreased CO) and decreased PVR
Adverse effects: Angioedema
(DO NOT USE WITH ALDOSTERONE ANTAGONISTS)
Suffix: “sartan” - e.g. eprosartan
DRIs
Mechanism of action
Adverse effects
Bind to and inhibit renin (rate limiting step in RAAS = affect whole pathway)
Adverse effects: Hyperkalemia, angioedema, diarrhea, persistent cough
Calcium Channel Blockers Difference between the two types Mechanism of action Adverse effects Suffix
Dihydropyridine - only blocks calcium channels in smooth muscle at therapeutic doses
Non-dihydropyridine - blocks both cardiac and smooth muscle calcium channels
Mechanism: Inhibition of calcium uptake reduces tone/contraction of smooth/cardiac muscle - decreasing PVR and CO
Suffix - “dipine”
Adverse effects:
-Dihydropyridine: headache, dizziness, skin rash, flushing, peripheral edema, reflex tachycardia
- Non-dihydropyridine” compromised cardiac function, dizziness, constipation, flushing, edema, headache
Centrally acting alpha 2 agonists
Mechanism of action
Adverse effects
Bind to and activate alpha 2 receptors in the brain stem –> decreased sympathetic outflow to smooth muscle and to the heart (decreased CO and PVR)
Adverse effects:
- drowsiness, dry mouth, rebound HTN
L-DOPA
Mechanism of action
Therapeutic benefit
Adverse effects
Inactive molecule that is actively transported across the BBB, then decarboxylated to become dopamine Increases available dopamine Often administered with carbidopa - inhibits peripheral metabolism Vitamin B6 (pyridoxine) speeds up the reaction (L-DOPA to dopamine)
Nausea, vomiting, Dyskinesia, cardiac dysrhythmia, orthostatic hypotension, psychosis
Dopamine agonist
Mechanism of action
Adverse effects
Directly activate post-synaptic dopamine receptors
Adverse effects: Hallucinations, Orthostatic hypotension, daytime drowsiness
Dopamine releasers
Mechanism of action
Adverse effects
Stimulate dopamine release from pre-synapatic nerve terminals
Block NMDA receptors (reduce dyskinesia side effect of L-DOPA - i.e. used in combination)
Block dopamine reuptake
Adverse effects: Nausea, vomitting, dizziness, Lethargy, Anticholinergic effects
Catecholamine-O-Methyltransferase inhibitor (COMT)
Mechanism of action
Adverse effects
Inhibits COMT, thus reducing methylation (and inhibition) of L-DOPA –> allows a greater drug fraction to reach the site of action
AEs: Hallucinations, vivid dreaming, nausea, orthostatic hypotension
MAOB inhibitor
Mechanism of action
Adverse effects
Inhibit Monoamine oxidase B and thus oxidative metabolism of L-DOPA and dopamine –> more conversion to dopamine in the brain + more dopamine available in nerve terminals to be released
AEs: Insomnia, orthostatic hypotension, dizziness
Anticholinergic drugs
Mechanism of action
Adverse effects
Block binding of Ach –> decreases urinary incontinence, salivation and diaphoresis
AEs: dry mouth, constipation, blurred vision, urinary retention, tachycardia
Cholinesterase inhibitors
Mechanism of action
Adverse effects
Inhibit cholinesterases and thus the metabolism of ACh –> more remains in the synaptic cleft
AEs: Diarrhea, Insomnia, Vomiting, nausea
NMDA receptor antagonists
Mechanism of action
Adverse effects
Block the NMDA receptor, decreasing calcium influx into the post-synaptic neuron –> prevents degradation of neurons
AEs: No Major Drug Adverse effects
Conventional Antipsychotics
Mechanism of action
Adverse effects
Block D2 (dopamine) receptors in the mesolimbic area of the brain Also block NE, histamine and ACh receptors
AEs: Anticholinergic effects, sedation, skin rash, fever, orthostatic hypotension, EPS
Atypical Antipsychotics
Mechanism of action
Adverse effects
Mainly block 5-HT1a and 5-HT2a receptors, and D2 receptors (minimally)
Adverse effects:
Type 2 diabetes risk, weight gain, sedation, orthostatic hypotension, anticholinergic effects