Obat-obat anti kolinergik, penyelamat hidup, dan anti

aritmia

Gama NatakusumawatiI1111017

OBAT ANTI ARITMIA

Causes of arrhythmias

Abnormal automaticity and abnormal generatoin of spurious impulses

Abnormal rhtmicity of the pace maker

Shift of the pace maker from the sinus node to another pace in the heart

Blocks and abnormal pathways of impulse transmission

Schematic representation of reentry

Penggolongan obat anti aritmia

Antiaritmia

Actions of antiarrhythmic drugs

Schematic diagram of the effects of Class IA agents

Class IB drug

Lidocaine• Actions: Lidocaine, a local anesthetic, shortens

Phase 3 repolarization and decreases the duration of the action potential.

• Therapeutic uses: Lidocaine is useful in treating ventricular arrhythmias arising during myocardial ischemia, such as during a myocardial infarction

• Pharmacokinetics: given intravenously because of extensive first-pass transformation by the liver, which precludes oral administration→ dealkylated and eliminated almost entirely by the liver; consequently, dosage adjustment → in patients with liver dysfunction or those taking drugs that lower hepatic blood flow, such as propranolol.

• Adverse effects: It shows little impairment of left ventricular function and has no negative inotropic effect. CNS effects → drowsiness, slurred speech, paresthesia, agitation, confusion, and convulsions. Cardiac arrhythmias may also occur.

Mexiletine• These Class IB drugs have actions similar to those of

lidocaine, and they can be administered orally. • used for chronic treatment of ventricular

arrhythmias associated with previous myocardial infarction.

Tocainide• Used for treatment of ventricular tachyarrhythmias.• Pulmonary toxicity, which may lead to pulmonary

fibrosis.

Schematic diagram of the effects of Class IB agents

Schematic diagram of the effects of Class IC agents

Class II Antiarrhythmic Drugs

• Class II agents are -adrenergic antagonists. These drugs diminish Phase 4 depolarization, thus depressing automaticity, prolonging AV conduction, and ↓ heart rate and contractility.

• Class II agents are useful in treating tachyarrhythmias caused by↑sympathetic activity. Also used for atrial flutter and fibrillation and for AV-nodal reentrant tachycardia.

• Propranolol→Reduces the incidence of sudden arrhythmic

death after myocardial infarction (the most common cause of death in this group of patients).

→The mortality rate in the first year after a heart attack is significantly reduced by propranolol, partly because of its ability to prevent ventricular arrhythmias.

Class III Antiarrhythmic DrugsAmiodarone• Actions: contains iodine and is related structurally to thyroxine. It has complex effects, showing Class I, II, III, and IV actions. Its

dominant effect is prolongation of the action potential duration and the refractory period.

Amiodarone has antianginal as well as antiarrhythmic activity.• Therapeutic uses: Amiodarone is effective in the treatment of severe refractory

supraventricular and ventricular tachyarrhythmias. Despite its side-effect profile, amiodarone is the most

commonly employed antiarrhythmic

• Adverse effects:Some of the more common effects include interstitial

pulmonary fibrosis, gastrointestinal tract intolerance, tremor, ataxia, dizziness, hyper- or hypothyroidism, liver toxicity, photosensitivity, neuropathy, muscle weakness, and blue skin discoloration caused by iodine accumulation in the skin.

recent clinical trials have shown that amiodarone does not reduce the incidence of sudden death or prolong survival in patients with congestive heart failure

Sotalol• A class III antiarrhythmic agent, also has potent

nonselective Beta-blocker activity. It is well established that beta blockers reduce mortality associated with acute myocardial infarction.

• Actions: blocks a rapid outward potassium current, known as the delayed rectifier. This blockade prolongs both repolarization and duration of the action potential, thus lengthening the effective refractory period.

• Therapeutic uses: used for long-term therapy to decrease the rate of sudden

death following an acute myocardial infarction. have a modest ability to suppress ectopic beats and to reduce myocardial oxygen demand.

strong antifibrillatory effects, particularly in the ischemic myocardium.

Sotalol was more effective in preventing recurrence of arrhythmia and in decreasing mortality than imipramine, mexiletine, procainamide, propafenone, and quinidine in patients with sustained ventricular tachycardia

• Adverse effects: This drug also has the lowest rate of acute or

long-term adverse effects prolong the QT intervalthe syndrome of torsade de pointes is a

serious potential adverse effect, typically seen in three to four percent of patients

Schematic diagram of the effects of Class III agents

Class IV Antiarrhythmic Drugs

• Class IV drugs are calcium-channel blockers .• They decrease the inward current carried by

calcium, resulting in a decreased rate of Phase 4 spontaneous depolarization.

• They also slow conduction in tissues that are dependent on calcium currents, such as the AV node.

• Although voltage-sensitive calcium channels occur in many different tissues, the major effect of calcium-channel blockers is on vascular smooth muscle and the heart.

Verapamil and diltiazem• Actions: Calcium enters cells by voltage-sensitive channels

and by receptor-operated channels that are controlled by the binding of agonists, such as catecholamines, to membrane receptors.

Calcium-channel blockers, such as verapamil and diltiazem, are more effective against the voltage-sensitive channels, causing a decrease in the slow inward current that triggers cardiac contraction

Schematic diagram of the effects of Class IV agents

• Therapeutic uses: Verapamil and diltiazem are more effective against atrial than

against ventricular arrhythmias. They are useful in treating reentrant supraventricular tachycardia and in reducing the ventricular rate in atrial flutter and fibrillation. In addition, these drugs are used to treat hypertension and angina.

• Pharmacokinetics: Verapamil and diltiazem are absorbed after oral

administration. Verapamil is extensively metabolized by the liver; thus, care

should be taken when administering this drug to patients with hepatic dysfunction.

• Adverse effects: Verapamil and diltiazem have negative

inotropic properties and, therefore, may be contraindicated in patients with preexisting depressed cardiac function.

Both drugs can also produce a decrease in blood pressure because of peripheral vasodilation an effect that is actually beneficial in treating hypertension

Other Antiarrhythmic DrugsDigoxinShortens the refractory period in atrial and ventricular

myocardial cells while prolonging the effective refractory period and diminishing conduction velocity in the AV node.

Used to control the ventricular response rate in atrial fibrillation and flutter.

At toxic concentrations, digoxin causes ectopic ventricular beats that may result in ventricular tachycardia and fibrillation. [Note: This arrhythmia is usually treated with lidocaine or phenytoin.]

Adenosine• Adenosine is a naturally occurring nucleoside, but

at high doses, the drug decreases conduction velocity, prolongs the refractory period, and decreases automaticity in the AV node.

• Intravenous adenosine is the drug of choice for abolishing acute supraventricular tachycardia.

• It has low toxicity but causes flushing, chest pain, and hypotension. Adenosine has an extremely short duration of action (approximately 15 seconds).

Cardiac impulse generation and conduction

OBAT ANTIKOLINERGIK

Gambar daerah kerja agonis kolinergik pada sistem saraf somatik dan atonomik

Gambar sintesis dan pelepasan asetilkolin dari neuron kolinergik

Reseptor kolinergik (kolinoseptor)

Berdasarkan perbedaan

afinitas terhadap zat yang mampu

meniru asetilkolin

(ACh)

R. Muskarinik R. Nikotinik

Reseptor Muskarinik

Afinitas kuat terhadap muskarin

Afinitas lemah terhadap nikotin

Terdiri dari subkelas : M1, M2, M3, M4, M5

Terdapat dlm ganglia SS perifer dan organ efektor otonom (jantung, otot polos, kel eksokrin)

Lebih dominan dalam kerja kolinergik

Reseptor Nikotinik

Afinitas kuat terhadap nikotin

Afinitas lemah terhadap muskarin

Terdpt di SSP, medula adrenalis, ganglia otonom, dan persambungan neuromuskular

Nikotin mula-2 memicu reseptor, tapi akhirnya justru menghambat

Subtipe dan karakteristik kolinoseptor

Subtipe Nama lain Lokasi Mekanisme

M1 M1a Saraf IP3; aliran DAG

M2 M2a; M2 jantung Jantung, saraf, otot polos

Penghambatan prod. cAMP; aktivasi kanal K+

M3 M2b; m2 kelenjar Kelenjar, otot

polos, endotelIP3; aliran DAG

M4’SSP ?? Penghambatan prod. cAMP

M5’ SSP ?? IP3; aliran DAG

NM Tipe otot, endplate receptor

Sambungan neuromuskular otot skelet

Depolarisasi kanal Na+ dan K+

NN Tipe neuronal, reseptor ganglion

Badan sel pascaganglion Depolarisasi kanal Na+ dan K+

a. Obat antimuskarinikObat golongan ini seperti atropin dan

skopolamin bekerja menyekat reseptor muskarinik yang menyebabkan hambatan semua fungsi muskarinik

Bertentangan dengan obat agonis kolinergik yang kegunaan terapeutiknya terbatas, maka obat penyekat kolinergik ini sangat menguntungkan dalam sejumlah besar situasi klinis

Obat-obat antimuskarinik : atropin, ipratropium, skopolamin

Kompetisi atropin dan skopolamin dengan asetilkolin untuk reseptor muskarinik

ATROPINGolongan antikolinergikINDIKASI:• Asystole/PEA (2nd line setelah adrenalin)• Unstable bradikardia• Keracunan kolinergik (organofosfat)SEDIAAN:Ampul 0,25 mg/ 1 mLDOSIS:• Asistol/PEA : 1 mg IV flush, diulang 3 – 5 menit (maks 3 mg)

2 – 3 mg dilarutkan dalam 10 ml NS• Bradikardia : 0,5 mg IV flush, diulang tiap 3 –5 menit (maks 3 mg) • Keracunan organofosfat: 1-2 mg, diulang tiap 2-5 menit sampai

terdapat tanda atropinisasi

EFEK:Meningkatkan konduksi HR naikMenurunkan sekresi klj antikolinergik

PERHATIAN:• Dapat memperburuk iskemia miokard (takikardi,

palpitasi)• Menyebabkan bradikardia paradoksal (< 0,5 mg)• Hipertensi, kejang • Tidak berguna untuk blok AV node derajat 2 tipe II

dan derajat 3

b. Obat penyekat neuromuskularObat ini menyekat transmisi kolinergik antara

ujung saraf motor dengan reseptor nikotinik pada cekungan neuromuskular otot rangka

Penyekat neuromuskular bermanfaat secara klinik selama operasi guna melemaskan otot secara sempurna tanpa memperbanyak obat anastesi yang sebanding dalam melemaskan otot.

Obat-obat penyekat neuromskular : atrakurium, doksakurium, metokurin, mivakurium, pankuronium, piperkuronium, rokuronium, suksinilkolin, tubokurarin, vekuronium

Daerah kerja antagonis kolinergik

OBAT PENYELAMAT HIDUP

ADRENALIN (EPINEPHRIN).INDIKASI:• VF, Pulseless VT, PEA, Asystole• Mengatasi gangguan sirkulasi (Syok distributif) • menghilangkan bronchospasme SEDIAAN:• ampul 1:1000 (1 mg/1 ml)/ ampul 1:10000 (0,1 mg / 1 ml)• Rute: IV flush, ET (2-3 x dosis IV), Infusion 1 mg/500 ml D5%/NS (2 ug/mL)

DOSIS:• CPR : 1 mg IV flush (diikuti 10 ml NS), diulang 3-5 menit

2- 2,5 mg ET (dilarutkan dlm 10 ml NS) • Anafilaktik: 0,5 mg SC/IM• Shock : infusion 1 ug/menit, titrasi sampai max 10 ug/mnt

• Bronkodilator : 0,3 mg SC (syarat kondisi jantung bagus)

• Meningkatkan kekuatan kontraksi jantung• Meningkatkan konduksi HR meningkat• Meningkatkan resistensi vaskuler BP naik

• mengubah “Fine Ventricular Fibrillation” menjadi “Coarse Ventricular Fibrillation” lebih mudah di DC

• Dosis besar dapat menyebabkan iskemia miokard, angina, dan peningkatan kebutuhan oksigen miokard

DOPAMINEINDIKASI:• Shock (refrakter terhadap pemberian cairan)• obat pilihan kedua untuk bradikardia simtomatis

(setelah atropin)• Hipotensi (TDS < 70 mmHg)SEDIAAN: Ampul 200 mg/ 5 mLDOSIS:• 2 – 5 ug/kg/menit meningkatkan renal blood flow• 5 – 10 ug/kg/mnt meningkatkan kontraksi

jantung• > 10 ug/kg/ mnt konstriksi sistemik

PERHATIAN:• Setelah target tercapai, turunkan bertahap

(tapering)• Jangan mencampur/melarutkan dengan

natrium bikarbonat, lakukan pengenceran dengan D5%, D5 1/2 NS, D10 0,18 NS; RL

• Diberikan dengan syringe pump atau infusion pump, harus selalu drip, bukan IV bolus

• Bisa menyebabkan takiaritmia, vasokonstriksi yang eksesif

DOBUTAMININDIKASI:• Dipertimbangkan untuk kasus pump problems

(gagal jantung kongestif, sembab paru/congestive pulmonum) dengan TDS 70 – 100 mmHg dan tidak ada tanda-tanda syok

SEDIAAN: Ampul 250 mg/ 10 mLDOSIS:• 2 – 20 µg/kg per menit, titrasi sehingga HR

tidak sampai meningkat 10 % dari baseline

PERHATIAN:• Cegah pemberian pada TDS < 100 mmHg dan

ada tanda-tanda syok• Menyebabkan takiaritmia• Tidak boleh mencampur dengan natrium

bikarbonat

MORFININDIKASI:• Chest pain dengan Acute Coronary Syndrome (ACS) yang

tak respon dengan nitrat• Edema paru akut kardiogenik (bila TD adekuat)

SEDIAAN: Ampul 10 mg/ 1 mLDOSIS:• Dosis inisial : 2 – 4 mg IV dalam 1 – 5 menit, setiap 5

sampai 30 menit• Dosis ulangan : 2 – 8 mg pada interval 5 sampai 15 menit• Masukkan pelan-pelan dan titrasi sampai tercapai efek

PERHATIAN• Tidak untuk infark inferior • Bisa menyebabkan depresi napas• Menyebabkan hipotensi (pada pasien dengan

deplesi volume cairan)• Gunakan dengan hati-hati/perhatian penuh

pada kasus infark ventrikel kanan• Antidotum : nalokson (0,4 – 2 mg IV)

ALHAMDULILLAH….