Calcium channel blockers Flashcards
Verapamil
Verapamil is a Phenylalkylamine
IC portion L-type alpha1 subunit
- Racemic mixture
- Dextroisomer- acts on fast NA channels - LA effect
- Levoisomer- Specific for l-type Ca channel -CCB
- Clinical use:
- Tx- supraventricular tachydysrhytmias - primary side of action AV node
- Vasospastic angina pectoris bc of vasodilatadory effect
- Symptomatic Hypertrophic cardiomiopathy with or without left ventricular outflow obstruction
- maternal and fetal tachydyrhytmias and premature labor- Administration IV to partiturent prolongs AV conduction on fetus despite limited placental transport.
- May decrese uterine blood flow- caution adm in partiturent with impared uteroplacental perfusion.
- Side Effect-
- negative chronotropic effect on SA node
- negative inotropic effect on SA node- seems to be exagerated in patient with preexisting left ventricular dysfunction- should not be administerd to patient with heart failure, severe bradycardia, sunis node dysfunction or AV node block.
- Moderate vasodilating effect on coronary and systemic arteries.
- may presipitate dysrhytmias in patients with Wolf-Parkinson-white syndrome.
Dyhidropyrimidines Nifedipine
- Great coronary and peripheral arterial vasodilator - activates baroreceptor- increases peripheral nervous system activity manifesting as , increase HR, SNS activity which counter acts the negative inotropic, chronotropic and dromotropic effect.
- may produce excesive myocardial depression, especially in patients with pre-existing left ventricular dysfunction or concominant therapy with b-blocker
Clinical Uses
- Adm PO 10 -30 mg- effect in 20 min peak 60-90 min
- Tx- angina pectories due to coronary vasospasm
Side Effects:
- Flushing
- vertigo
- headache
- peripheral edema ( venodilation)
- hypotension, paresthesia
- skeletal muscle weakness
- may induce renal dysfunction
Dyhidropyrimidines Nicardipine
Greates vasodilating effect of all CCB with vasodilating being prominent in coronary arteries.
can be combinine with b-blocker for tx of angina
Either nifedipine or nicardipine may be particularly useful in patient who have residual hypertension despite b-block
Long elimination halt time- 72hrs should elapse before increasing oral dose
- Side effect: similar to nifedipine
- Clinical Uses:
- tocolitic drugs having similar effect as salbuterol with fewer side effedcts.
- binds to the inside of myometrial L type CC, causing them to remain closed inhibiting uterine contractility
- can cause pulmonary edema
- Also blunts hemodynamic response of electroconvulsive therapy 40 mg /kg IV
Dyhidropyrimidines Nimodipine
- Lipid solubility allows it’s entrance in BBB
- Clocks the influx of EC Ca neccessary for contraction of large cerebral arteries
Clinical Use:
- treats patients with subarachnoid hemorrage
- precents or attenuates cerebral vasospasm that often accompanies subarachnoid hemorrage.
Initial dose- 0.7mg/kg followed by 0.35 mg/kg every 4 hr for 21 day
Blood and CSF levels with dosis are 6.9ng/ml and 0.77ng/ml
If patient is comatouse adm in nasogastric tube with 30 ml of saline
Signs of excess administration- peripheral vasodilation, hypotension
Also has been evaluated for cerebral protection after global ischemia
Dyhidropyrimidine Amlodipine
PO 5-10mg
Provides anti-ischemic effect in patients with acute coronary syndrome
Combination of amlodipine and B-blocker more effective in MI
Dialtizem Benzothiazepines
- CCB alpha1
- acts at soudium-potassium pump
- calcium calmodulin binding
- First line medication for treatment of supraventriculas tachydirythmias
- Blocks Ca lcium channel at the AV node
- Chronic control of essential HTN
- effects of SA, AV node and vasodilating effect appear to be intermidiate between verapamil and dyhidropiridines
- has minimal cardio depressant effect
Uso clinico: Manejo de angina pectori
IV 0.25-0.35 mg/kg over 2 min repeat in 15 min
After initial dose can be given in continous infusion for 24 hrs 10mg/hr
