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HHSC Base Hospital ProgramEMS Pharmacology – unit 1

Reading Between the Lines

By; Neil Freckleton

March, 2006 HHSC Paramedic Base Hospital Program


Acknowledgement

York Region Base Hospital Pharmacology Package and Niagara Base Hospital program Jason Primrose Jim Harris, Program Manager David Austin, MD FRCP (C) Medical Director March, 2006, Niagara Base Hospital, Rick Ferron,

A/Education Coordinator


Understanding Patient Meds

The medication bottles can often speak for the patient who cannot speak for themselvesUnreliable medical historianLanguage barrierPt. unconscious


Didacticogenic Craniomyalgia

Education-caused head pain. When you learn so much that your head starts to hurt.



What medical history might the patient whose med list includes the following medications have? lanoxinmetoprololAllopurinolClick here for the answer



Even when you know the patient’s medical history, their medications might tell you how severe a patient’s illness is.



Medications often alter physiological response.

Can cause patient presentation to be misleading



At least 10% of hospital admissions from medication side effects, allergic reactions and overdoses.

Knowing actions of drugs can help increase index of suspicion for medication effects


First: Where to locate Pt. Meds

Medicine cabinetKitchen cupboard beside sinkPantryBedsideIn a tray on dining room or living room

tableOccasionally refrigeratorList in wallet/purseMARS


Generic vs. Trade Names

Generic name = chemical nameGeneric drugs are chemically equivalent

to brand name drugs, but cost a lot less e.g., penicillin--"generic" namePen VK--"brand name" used to identify a

specific drug company's own particular brand of penicillin


Common Med Short Forms

‘ii po qid pc & hs’ Click here Short forms used for documentation,

sometimes found on MARS (Medication Administration Record Sheet).

Knowledge of short forms not only helpful for reading documentation, but allows for more complete forms

Professionalism


Common Med Short FormsLatin Abbreviation Meaning

ante cibum ac before meals bis in die bid twice a day gutta gt drop i = one hora somni hs at bedtime ii = two oculus dexter od right eye iii = three oculus sinister os left eye per os po by mouth post cibum pc after meals pro re nata prn as needed quaque 3 hora q3h every 3 hours quaque die qd every day quater in die qid 4 times a day ter in die tid 3 times a day


Pharmacokinetics

The study of the basic processes that determine the duration and intensity of a drug’s effect. Four processes are:AbsorptionDistributionBiotransformationElimination


Pharmacodynamics

The study of the mechanisms by which specific drug dosages act to produce biochemical or physiological changes in the body.


Pharmacodynamics

Mechanisms of action: binding to a receptor site, changing physical properties, chemically combining with other substances, altering a normal metabolic pathway

Drug Potency and Efficacy

Therapeutic Index

Factors Altering Drug Response


Factors Altering Drug Response

AgeBody MassGenderEnvironment (e.g. antianxiety meds)Time of administrationPathologic stateGenetic factorsPsychological factors


Geriatric Patients

How pharmokinetics/dynamics are affected in elderly patients:Decreased cardiac outputDecreased renal functionDecreased brain massDecreased total body waterDecreased body fatDecreased serum albuminDecreased respiratory capacity


Pregnant Patients

Increased cardiac outputIncreased heart rateIncreased blood volume (up to 45%)Decreased protein bindingDecreased hepatic metabolismDecreased blood pressurePlacental barrier permeability/lactation

(effects on child)


Drug Classes

Drugs can by referred to by makeupHormoneCarbohydrate

By actionBeta blockersACE Inhibitors

Or by therapeutic affectAntiarrhythmicsAntianginals


Drug ‘Classes’

Drugs affecting the CNSDrugs affecting the ANSDrugs used to treat cardiovascular

systemDrugs affecting other systems

RespiratoryHormonesGI


Drugs affecting the Central Nervous System

Anxiolytic/hypnotics*CNS stimulantsAnaestheticsAntidepressants*Neuroleptics*Opioid analgesics and antagonistsAnticonvulsants*


Drugs Affecting the ANS

Cholinergic AgonistsCholinergic AntagonistsAdrenergic AgonistsAdrenergic Antagonists


Drugs Affecting Cardiovascular System

AntiarrhythmicsAntihypertensives AntianginalsAnticoagulantsTreatment of CHF Antihyperlipidemics


Others

Respiratory DrugsDiureticsGI/AntiemeticsHormonesInsulin/Oral HypoglycemicsSteroids


Cardiovascular System Drugs

Treatment of CHFAntiarrhythmic DrugsAntianginal DrugsAntihypertensive DrugsAnticoagulants


Aims of Heart Failure Management

To achieve improvement in symptoms Nitro Digoxin ACE inhibitors Diuretics

To achieve improvement in survival ACE inhibitors ß blockers (for example, carvedilol and bisoprolol) Oral nitrates plus hydralazine


Treatment of CHF

VasodilatorsACE inhibitors (ramipril-Altace)hydralazine (Apresoline) isosorbide (Isordil, Nitrobid)minoxidil (Loniten-also Rogaine)sodium nitroprusside (Nipride)

DiureticsInotropic agents

digoxin (Lanoxin)


Vasodilators

Increase heart ratePostural hypotension/syncopeMUST be used with diuretic—some

activate renin release, can lead to compensatory water retention

Angioedema-edema involving face, larynx—stridor, etc. !!


Antiarrhythmics

Vaughn-Williams Classification: Class I – Sodium channel blockers Class II – Beta blockers Class III – Potassium channel blockers Class IV – Calcium channel blockers Other – Cardiotonic gycosides

--Adenosine


Cardiac Conduction Cycle

Na+ Influx (fast sodium channels)

K+ efluxK+ eflux and Ca+ influx (plateau)

K+ eflux

Resting Membrane Potential (leaky Na+)


Antiarrhythmics

Class I - Sodium Channel BlockersClass Ia

disopyramide – Norpace, Rhythmodanprocainamide – Pronestylquinidine – Cin-Quin

Class Ib lidocaine – Xylocainephenytoin – Dilantin tocainide - Tonocard


Antiarrhythmics

Sodium Channel BlockersClass Ic

encainide – Enkaid flecainide – Tambocorpropafenone – Rhythmonorm, Rhythmol SR

Class II – Beta Blockers


Beta Blockers

Beta BlockersBlock effects of catecholamines (e.g.

norepinephrine) at Beta receptors.

Heart Effects:Chronotropic: reduce heart rate Inotropic: reduce contractilityDromotropic: slows conduction

Angina Tx: reduce HR, contractility, MVO2


Beta Blockers

Beta BlockersSelective vs. Non-Selective

1 vs. 2 receptors1 selective is preferred in patients with asthma,

peripheral vascular disease and diabetes**.

Other uses: Hypertension, prevention of further MI’s, dysrhythmias, migraines.


Beta Blockers

Selective 1 Blockers atenolol – Tenormin betaxolol – Kerlone carteolol – Cartol penbutolol – Levatol metoprolol-Lopressor

Non-Selective nadolol – Corgard oxprenolol – Trasicor pindolol – Visken propranolol – Inderal timolol - Blocadren


Beta Blockers

Beta BlockersPrecautions:

Heart failureBradycardiaHeart BlockBronchospasm (non-selective)Diabetics (non-selective)Other drugs with similar actions (e.g. Verapamil)May decrease compensatory response


Antiarrhythmics

Class III – Potassium Channel Blockersamiodarone (Cordarone-some effects from

other classes)bretylium – Breylol

Class IV – Calcium Channel Blockersnifedipine – Adalatverapamil – Isoptindiltiazem - Cardizem


Calcium Channel Blockers

Calcium Channel Blockers (CCBs) Block entry of calcium into cell during (prolonged

plateau phase--phase 2--of depolarization) which results in:

Vasodilation Reduced cardiac contractility Slow impulse conduction

Also used in Angina: Improves blood flow Reduces cardiac contractility, work and MVO2 Prinz-Metals Angina (Vasospastic)



Common suffix -dipinenifedipine – Adalat, Procardiaverapamil – Isoptindiltiazem – Cardizemamlodipine – Norvascbepridil – Vascornicardipine – Cardene felodipine – Plendil isradipine – Dynacircnimodipine - Nimotop



Side effects related to vasodilatory actionsHeadacheFlushingPalpitationAnkle edema

Less common with slow release products like amlopidine (Norvasc)


CCB Overdose

CCBs have replaced TCAs as one of most common potentially lethal prescription drug overdoses

The most commonly prescribed cardiovascular drugs in the United States

Designated by poison control centres as a member of the ‘one pill can kill’ club, especially for peds.


CCB Overdose

Treatment plan includes airway management and fluid replacement, control arrhythmias and BP (dopamine?).

Patient requires calcium supplementation, high dose glucagon

Possible high-dose insulin, pacemaker placement, aortic balloon pump


Cardiac Glycosides

digoxin (Lanoxin)digitalis Inhibits Na+, K+-ATPase.

Increase inward current of Ca++Positive Inotrope (contractility)Negative Chronotrope (rate)Negative Dromotrope (speed of conduction)

Controls ventricular response rate in A-fib and A-flutter


Digoxin

Special note: also strengthens cardiac contraction; sometimes used for CHF, in combination with diuretics, especially furosemide and potassium, e.g., Slow-K. *

Toxicity and accidental overdose happen fairly often. Becomes toxic easily if potassium is low.

Signs of toxicity include bradycardia, confusion, fatigue, abdominal pain, and visual disturbances (halos around lights, yellowed colour vision). Also vertigo and anorexia possible.


Digoxin

‘dig toxicity’ also look for:Rhythm disturbances (2nd degree Type I-

Wenckeback, PVCs, PAT, MAT with block, atrial or junctional bradycardias with AV dissociation—Atropine!

‘digitalis effect’--Characteristic ‘slurring’ of s-t segment on 12-lead normal for digoxin use.


Digitalis effect

‘scooped’ S-T depression


Drugs used to treat Hypertension

DiureticsBeta BlockersACE InhibitorsAngiotensin Receptor BlockersCalcium Channel BlockersAldosterone AntagonistsAlpha-1 Antagonists (covered in ANS

drugs)


Diuretics

ThiazidesPotassium SparingLoop Diuretics


Thiazide Diuretics

inhibit Na+ and Cl- transport in the cortical thick ascending limb and early distal tubule.

They have a milder diuretic action than do the loop diuretics because this nephron site reabsorbs less Na+ than the thick ascending limb--appropriate for long-term use


Thiazide Diuretics

hydrochlorothiazide (Novo-Hydrazide, Apo-Hydro, Diuchlor H, HydroDIURIL, Neo-Codema, Urozide)

methyclothiazide (Duretic), chlorthalidone (Hygroton, Uridon, Novo-

Thalidone, Apo-Chlorthalidone)bendroflumethiazide (Naturetin)metolazone (Zaroxolyn)


Potassium-Sparing Diuretics

spironolactone (Novospiroton, Aldactone) is a competitive antagonist of aldosterone

triamtrene, amiloride affect absorption of Na+ in nephron where it has less influence on K+ transport (late distal tubule)


Loop Diuretics

more powerful and are especially useful in emergencies. furosemide (Apo-Furosemide, Lasix,

Novosemide, Uritol )ethacrynic acid (Edecrin)


Beta Blockers

Used with caution in presence of CHF—can exacerbate CHF.

Discussed under ‘Antiarrhythmics’


ACE Inhibitors

Angiontensin-Converting Enzyme Inhibitors

Inhibit conversion of Angiotensin I to Angtiotensin II (= vasodilation)

Used for Tx of Hypertension without altering myocardial function

Also used to treat CHF


ACE Inhibitors (cont’d)

Often indicated with suffix –prilcaptopril (Capoten)enalapril (Vasotec) fosinopril (Monopril) lisinopril (Zestril) ramipril (Altace)quinapril (Accupril)moexipril (Unipril)


Common Side Effects

May cause BP to be too low = fatigue, syncope

Inhibits compensatory response = very sensitive to fluid drops

Overdose-hypotension, especially if mixed with diuretic. Possible tachycardic response (compensating).


Angioedema

Rare, more common in patients of Afro-Caribbean origin

Treated with epinephrine, benadryl


Angiotensin Receptor Blockers

Block vasoconstriction caused by Angiotensin II

Usually carry suffix –sartan or –sarten losartan (Cozaar)valsartan (Diovan)candesarten (Atacand) irbesarten (Avapro)


Anticoagulants

Coumadin/Warfarinplatelet inhibitors

ASA (Asaphen, Entrophen) ticlopidine HCL (Ticlid) clopidogrel (Plavix) dipyridamole (Persantine)


ASA

Overdose: common with ASAASA: Directly stimulates respiratory

centre in brain=involuntary hyperventilation (and respiratory alkalosis)

Also causes metabolic acidosis (mixed acid/base disturbance)


ASA Overdose

Symptoms:HyperventilationTinnitisDiaphoresis, high feverConfusion/lethargy*VomitingPoss. Hypoglycemia

Tx-supportive


Hypoglycemic agents


metformin (Glucophage)

Only drug of its typeCauses less glucose to be released from

storage in liverDoes not increase insulin secretion, so

risk of hypoglycemia less than glyburide


Carbohydrate Absorption Inhibitor

acarbose (Prandase)Interferes with carbohydrate absorption

from the GI tract—blood glucose levels do not rise as quickly

Does not cause hypoglycemia—does not increase insulin levels or sensitivity

Reduces effectiveness of oral glucoseActs synergistically with insulin and ADB


Oral Hypoglycemics

All oral hypoglycemics have long half-life—effect is maintained for days

Pt. who takes OD or who becomes symptomatically hypoglycemic needs to be transported/monitored closely


Acetaminophen (Tylenol)

Non-Narcotic Analgesic, AntipyreticPreferred fever med. for pediatricsMidol, also combined with narcotic

analgesics in Darvocet, Hydrocet, Oxycocet and Percocet

Common source of overdose—readily accesible and common in ”pseudosuicides” (where pt. perceives drug as relatively safe)


acetaminophen Overdose

Pt. asymptomatic; by the time symptoms appear, irreversible liver damage has occurred.

NO CNS depressant properties; if pt. presents with altered LOC, look for other causes

Dose of 6 g (12 extra strength, 15-18 reg. strength) considered serous in adult. For child, any dose over 150 mg/kg serious.

EMS treatment: supportive.**


Pharmacology

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