Pharmacy Practice

Practice of Pharmacy Notes

Module 3 Overview

  • Module 3: Practice of Pharmacy

    • Lecturer: Darwin I. Carrido, RPh

Table of Specifications

  • Competency Weighting and Difficulty Levels:

    • Table outlines the breakdown of topics, their weight in percentage, and the number of items for each cognitive level (Knowledge, Comprehension, Application, Analysis, Synthesis, Evaluation).

    • Total items: 100

    • Compounding/Dispensing: 21%

    • Clinical Pharmacy: 37%

    • Hospital Pharmacy: 21%

    • Pharmaceutical Calculations: 21%

Compounding and Dispensing (21%)

  • Introduction to Compounding and Dispensing

  • The Prescription

  • Compounding and Dispensing processes

  • Adverse Drug Reactions (ADRs)

  • Medication Errors

  • Incompatibilities

  • Drug Interactions

Clinical Pharmacy (37%)

  • Introduction to Clinical Pharmacy

  • Clinical Pharmacist as Communicator

  • The Medical Chart

  • Diagnostic Laboratory Examination

  • Pharmacist Intervention in Clinical Pharmacy

  • Disease Orientation and Management

  • Top morbidity and mortality in the Philippines

Hospital Pharmacy (21%)

  • Introduction to Hospital Pharmacy

  • Hospital and its Organization

  • Hospital Pharmacy Department

  • Pharmacy and Therapeutics Committee (PTC)

  • Hospital Formulary

  • Management and Control

  • Special Preparations

  • Drug Distribution System

Pharmaceutical Calculations (21%)

  • Fundamentals of Measurement and Calculations

  • Different systems of weights and measurements and conversions

  • Interpretation of the Prescription and Medication Order

  • Density, Specific Gravity and Specific Volume, Weights and Volumes of Liquids

  • Concentration Expressions

  • Calculation of Doses

  • Calculations involving units, microgram/milligram, and other measures of potency

  • Isotonic Solutions

  • Electrolyte Solutions

  • Dilution and Concentration

  • Reducing and Enlarging Formula

  • Body Mass Index and Nutrition Label

  • Thermometry

  • Proof Strength

  • Drug Pricing

Compounding vs. Dispensing

  • Compounding: The sum of processes performed by a pharmacist in drug preparation, including calculations, mixing, assembling, packaging, or labeling of a drug as the result of a prescription or drug order.

  • Dispensing (IRR of RA 10918): The sum of processes performed by a pharmacist from reading, validating, and interpreting prescriptions; preparing; packaging; labeling; record keeping; dose calculations; and counseling.

  • Dispensing (A.O. 62 series of 1989): The act by a validly registered pharmacist of filling a prescription or doctor's order on the patient's chart.

  • Generic Dispensing: Dispensing the patient's/buyer's choice from among generic equivalents.

  • Partial filling of prescription: Dispensing less than the total number of units prescribed.

  • Drug Outlet: Drugstores, pharmacy, and other business establishments which sell drugs or medicines.

  • R.A. 10918: Scope of pharmacy practice includes dispensing pharmaceutical products in situations where supervision is required (EXCLUSIVE).

  • Compounding (IRR of RA 10918): The sum of processes performed by a pharmacist in drug preparation including calculations, mixing, assembling, packaging, or labeling of a drug as the result of a prescription or drug order. Also, for research, teaching, or chemical analysis.

  • Compounded Prescriptions: Require extemporaneous compounding or small-scale mixing of ingredients by the pharmacist to meet specific patient needs.

  • Pharmaceutical Compounding: Involves mixing, assembling, packaging, and labeling a medication on receipt of a prescription order for a specific patient.

  • Compounding vs. Manufacturing: Compounding is NOT manufacturing, which involves large-scale production, packaging, and promotion of drugs for resale.

Dispensing Cycle

  1. Receive and validate prescription.

  2. Understand and interpret prescription.

  3. Prepare and label items for issue.

  4. Make a final check: patient, medicine, dose.

  5. Record action taken.

  6. Issue medicine to patient with clear instructions and advice.

Parts of a Prescription

  1. Prescriber Information

  2. Patient Information

  3. Date of Prescription

  4. Superscription (Take thou, you take, recipe)

  5. Inscription (Medication prescribed)

  6. Subscription (Dispensing direction)

  7. Transcription (Direction for patient)

  8. Special Instructions

Prescription Errors

  • Erroneous Prescription

  • Violative Prescription

  • Impossible Prescription

  • Where the brand name precedes the generic name

  • Where the generic name is the one in parenthesis

  • Where the brand name is not in parentheses

  • Where generic name is not written

  • Where the generic name is not legible and a brand name which is legible is written

  • When the brand name is indicated and instructions added (such as the phrase "no substitution") which tend to obstruct, hinder or prevent proper generic dispensing.

  • When only the generic name is written but it is not legible.

  • When the generic name does not correspond to the brand name.

  • When both the generic name and the brand name are not legible

  • When the drug product prescribed is not registered with FDA

Action on Prescription Errors by Pharmacist

  • Erroneous prescription shall be filled. Such prescription shall be kept and reported by the pharmacist to the nearest DOH office for proper action.

  • Violative or Impossible prescriptions shall not be filled. They shall be kept and reported to the nearest DOH office for appropriate action.

  • Reporting should be done within 3 months.

Special Prescription

  • Used for dangerous drugs issued by the Philippine Drug Enforcement Agency (PDEA).

    • Triplicate copy:

      • Yellow – Pharmacist

      • White – Patient (retains prescription)

      • Blue – Physician

Philippine Schedules for Dangerous Drugs

  • Lists generic names of Philippine FDA-registered drug preparations.

  • See list of brand names on PDEA website (www.pdea.gov.ph)

  • Philippine Schedule I: No currently accepted medical use; lacks accepted safety.

  • Philippine Schedule II: May have accepted medical use; high potential for abuse leading to severe dependence.

    • Examples: Fentanyl, Morphine, Oxycodone, Pethidine, Methylphenidate, Remifentanil

  • Philippine Schedule III: Accepted medical use; potential for abuse less than Schedule I and II drugs, leading to moderate or low physical dependence or high psychological dependence.

    • Examples: Buprenorphine, Pentobarbital

  • Philippine Schedule IV: Accepted medical use; low potential for abuse less than Schedule III drugs, leading to limited physical or psychological dependence.

    • Examples: Alprazolam, Bromazepam, Clonazepam, Clorazepate, Diazepam, Midazolam, Phenobarbital, Phentermine, Zolpidem

  • Philippine Schedule V: Accepted medical use; potential for abuse that may lead to from low to high psychological or physical dependence. (Dangerous Drugs in the Philippines only).

    • Examples: Ephedrine, Ketamine, Nalbuphine

Medication Order

  • The doctor’s order on the patient’s chart for the use of specific drugs.

  • Commonly used in the hospital/institutional setting; considered a prescription in the law.

  • Amount can vary depending on the institution.

Symbols and Abbreviations in Prescriptions

  • Standard abbreviations, acronyms, and symbols are needed to avoid medication errors.

  • The Joint Commission requires healthcare organizations to standardize abbreviations, acronyms, and symbols and to create a do-not-use list.

Common Abbreviations

  • aa: ana, of each

  • a.c.: ante cibos, before meals

  • ad: ad, to; up to

  • a.d.: aurio dextra, right ear

  • ad lib: ad libitum, at pleasure

  • amp: ampula, ampule

  • aq: aqua, water

  • a.s.: auris sinistro, left ear

  • a.u.: auris utrae, each ear

  • add: adde; addatur, add

  • bid: bis in die, twice a day

  • caps: capsula, capsules

  • cong/ c: congius, a gallon

  • cum/ c: cum, with

  • DC or D/C: discontinue medication

  • div.: dividatur, divide

  • d.t.d.: dentur tales doses, give of such dose

  • ft: fiat, make; let it be made

  • gtt: gutta, drops

  • h.s.: hora somni, at bedtime

  • IM: intramuscular

  • IV: intravenous

  • IU: international units

  • M: misce, mix

  • Non rep or NR: non repetatur, do not repeat

  • Noct: at night

  • O: octarius, pint

  • o.d.: oculo dextro, right eye

  • o.s.: oculo sinistro, left eye

  • o.l.: oculo laevus, left eye

  • o.u.: oculo utro, each eye

  • p.c.: post cibum, after meals

  • p.o.: per os, by mouth

  • pr or rect: per rectum, rectally

  • prn: pro re nata, as needed

  • q: quaeque, each; every

  • qd: quotide, every day

  • qid: quarter in die, four times a day

  • qh: quaeque hora, every hour

  • qs: quantum sufficit, a sufficient quantity

  • rept: repetatur, let it be repeated

  • RTC: round the clock

  • s or $\bar{s}$: sine, without

  • sig.: signa, write or mark

  • Solv.: solve, dissolve

  • ss or $\bar{ss}$: semi, one-half

  • stat: statim, immediately

  • sec. art.: secundum artem, according to the art

  • tid: ter in die, three times a day

  • top: topically

  • ung.: unguentum, ointment

  • ut. dict. or ud: ut dict, as directed

  • wk: week

ISMP Error-Prone Abbreviations

  • List of error-prone abbreviations, symbols, and dose designations from the Institute for Safe Medication Practices (ISMP).

  • These abbreviations, symbols, and dose designations should NEVER be used when communicating medical information.

Symbols & Designations to Avoid (Examples):

  • μg: Use mcg

  • AD, AS, AU: Use "right ear," "left ear," or "each ear"

  • OD, OS, OU: Use "right eye," "left eye," or "each eye"

  • BT: Use "bedtime"

  • cc: Use "mL"

  • D/C: Use "discharge" and "discontinue"

  • IJ: Use "injection"

  • IN: Use "intranasal" or "NAS"

  • HS: Use "half-strength" or "bedtime"

  • hs: Use "at bedtime"

  • IU: Use "units"

  • o.d. or OD: Use "daily"

  • OJ: Use "orange juice"

  • Per os: Use "PO," "by mouth," or "orally"

  • q.d. or QD: Use "daily"

  • qhs: Use "nightly"

  • qn: Use "nightly" or "at bedtime"

  • q.o.d. or QOD: Use "every other day"

  • Daily: Use "daily"

  • q6PM, etc.: Use "daily at 6 PM" or "6 PM daily"

  • SC, SQ, sub q: Use "subcut" or "subcutaneously"

  • SS: Spell out "sliding scale;" use "one-half" or "1/2"

  • SSRI: Spell out "sliding scale (insulin)"

  • SSI: Use "1 daily"

  • i/d: Use "3 times weekly"

  • U or u: Use "unit"

  • UD: Use "as directed"

Standardized Dosing Times

Standard times for medication administration:
*Daily: 0900
*2 times a day (BID): 0900, 2100
*3 times a day (TID): 0900, 1400, 2100
*4 times a day (QID): 0800, 1200, 1700 (52 Psych)
*5 times a day: 0900, 1300, 1700, 2100
*Every 3 hours: 0000, 0300, 0600, 0900, 1200, 1500, 1800, 2100
*Every 4 hours: 0100, 0500, 0900, 1300, 1700, 2100
*Every 6 hours: 0600, 1200, 1800, 2400
*Every 8 hours: 0800, 1600, 2400
*Every 12 hours: 0900, 2100
*Every 24 hours: Time will default to hour profiled (i.e. 1st order processed)
*Bedtime: 2100
*With meals: 0800, 1200, 1700
*With meals and at bedtime: 0800, 1200, 1700, 2100
*Injectable antibiotics: Times determined by the time the 1st dose is processed

Incompatibilities

  • Incompatibilities are problems that may arise such as changes in appearance and efficacy when two or more drugs are combined, which may occur during compounding, dispensing, and administration.

Types of Incompatibilities:

  • Physical

    • Most easily detected by visible changes

    • Particulate formation

    • Haze

    • Precipitation

    • Color changes

    • Gas evolution

  • Chemical

    • Result in decomposition of the drug due to oxidation, reduction, hydrolysis, decomposition

    • Can be detected with a suitable analytic method

    • Loss of potency of >10%

    • Can also manifest through turbidity, precipitation, or color changes

  • Therapeutic

    • A drug combination results in undesirable antagonistic or synergistic pharmacologic activity

    • Affect the body when administered.

    • LOCATION: In Vivo

  • Therapeutic Incompatibilities

    • aka Drug Interactions

    • When the effects of one drug are changed by the presence of another drug, herbal medicine, food, drink, or some environmental chemical agent.

Incidence of Drug Interactions

  • More Drugs = More Interactions

  • At-risk groups for Polypharmacy:

    • Elderly + Multiple Medications + Decreased Kidney Function

    • Multiple Conditions = Multiple Medications

Questions to consider

  • Should all interactions be avoided?

Effects of Drug Interactions

  • Harmful

    • Increase in Toxicity

    • Decrease in Efficacy

  • Beneficial

    • Decrease in Toxicity

    • Increase in Efficacy

Examples

  • Harmful:

    • MAOIs + Tyramine-Rich foods (e.g. Cheese) -> Hypertensive Crisis

    • Statins + Azole antifungals -> Muscle Damage

    • Warfarin + Rifampicin -> Decreased anticoagulant effect

    • Tetracycline/Quinolones + Dairy -> Decreased antibiotic activity

  • Beneficial:

    • Anti-hypertensives + Diuretics -> Increased antihypertensive effect

    • Magnesium + Aluminum -> Decreased diarrhea/constipation

Therapeutic Incompatibilities Examples

  • Drug - food (nutrient)

  • Drug - laboratory test

  • Drug - drug

  • Drug - herb

  • Drug - patient

  • Drug - procedure

  • Drug - environment

Drug and Food Interaction

  • Factors affecting Drug-Food Interaction

    1. Formulation characteristics

    2. Type of Food

    3. Ingested relative time of food and drug intake

  • As a general rule, this interaction is minimized if drug is taken 1 hr before a meal and 2 hrs after a meal

Physiological Effects of Food in Drug Interaction

  • Reduce gastric irritation

    • Intervention for drugs that cause gastric irritation (eg NSAIDS)

  • Reduce gastric emptying rate

    • Food and large volume of fluid improves the dissolution characteristics that will stimulate GER and minimizes degradation and improved absorption.

  • Stimulate gastric secretion of digestive enzymes, acids, and bile.

  • Formation of insoluble chelates

    • Tetracycline with Calcium

  • Enhanced hepatic blood flow and increased drug plasma concentration minimizing 1st pass effect

    • Propanolol and metoprolol

  • Increased or decreased bioavailability of drugs

    • Increased:

      • Vit B2: increased bioavailability because it results in a decrease of intestinal transit rate which means drug will stay longer in the absorption site

      • Lipophilic compounds + fatty meal (eg. Griseofulvin, itraconazole, tetracycline, theophylline, rifampicin, and INH)

    • Decreased:

      • Diazepam, clobazepam, Penicillin antibiotics (Ampicillin, Cloxacillin and Pen G oral)

Common Foods that interact with drugs

  • Alcohol/Acoholic Beverages

    • Decreases clearance of drugs (Acute intake)

      • Volume of blood containing the drug that is removed from a particular organ per unit time (closely related to elimination rate)

    • Increases Clearance (Chronic Alcoholism)

      • Stimulates Liver Enzymes/Metabolism

  • Tea and Coffee

    • Caffeine increases bioavailability of drugs

      • Paracetamol

      • Ergotamine

      • Nitrofurantoin

  • Tobacco (cigarette)

    • Polycyclic hydrocarbons particularly benzo-α-pyrene and 3-methyl-cholanthrene are potent enzyme inducers of drug metabolism and increase elimination

      • Diazepam

      • Warfarin

      • Theophyline

      • Propranolol

      • Chlorpromazine

  • Green leafy vegetables vs anticoagulants

    • Vitamin K present on green leafy vegetables would antagonize the effect of anticoagulants such as warfarin.

  • Milk and Dairy products vs cardiac glycosides and tetracyclines

  • Foods with pressor amines vs MAO inhibitors

    • Histamine, serotonin, Tryptamine, Tyramine

    • Antidepressant drug phenelzine, isocarboxazid when taken with foods rich in pressor amines may result in BP fluctuations particularly an increase in BP.

    • Tomatoes, Cheese, Banana, Pineapple, Passion fruit, Lemons, Chicken liver, Red wine

Other Drug-Nutrient Interactions

  • phenytoin + alcohol -> enhanced metabolism of phenytoin

  • tetracycline + dairy products -> impaired tetracycline absorption

  • theophylline + caffeine -> potential for toxic effects

  • warfarin + foods rich in vitamin K -> decreased anticoagulant response

  • drugs + grapefruit juice -> enzyme inhibition

  • disulfiram + alcohol -> hang-over effects: nausea, blurred vision, chest pain, dizziness, fainting

  • 1st gen sulfonylureas + alcohol,

  • metronidazole + alcohol,

  • cephalosphorins + alcohol -> disulfiram-like reactions

  • spironolactone + foods rich in K+ -> hyperkalemia

Other Drug-Herb Interactions

  • St. John’s wort + digoxin -> decrease digoxin levels

  • garlic + warfarin -> may increase INR with warfarin

  • ginseng + warfarin -> decrease INR with warfarin

  • valerian + sedative-hypnotics -> increased sedation

Drug - Lab Test Interaction

  • aka Drug Chemical Substance Interaction

  • Drugs & Metabolites that may color the urine

    • Rifampicin (red)

    • Vit B2 Riboflavin

    • Aminosalicylic acid

    • Anthraquinone derivative

    • Chloroquine

Drugs that interfere with urine glucose determination

  • Penicillin

  • Streptomycin

  • Chloramphenicol

  • INH

  • Vitamin C

    • reacts with copper in Copper sulfate of the benedict’s reagent giving false positive result for sugar.

Drugs that interfere with blood cholesterol levels

  • Increase:

    • Allopurinol, Anabolic steroids, Disulfiram, Estrogen, Furosemide

  • Decrease

    • Ascorbic Acid, Anti-diabetic Drugs, EDTA, Neomycin

Drugs that interfere with thyroid function tests

  • Chlordiazepoxide (antianxiety drug) decreases Iodine uptake

Drug-Drug Interactions

  • Receptor – complex molecule that bind/ interact with an active molecule such as drug or hormone

  • Affinity – Ability to bind with receptors

  • Intrinsic Activity/Efficacy

  • Drug + Receptor → Drug-receptor complex = Response

  • Potency – Amount or concentration of drug to elicit pharmacologic response

Agonist

  • Drug which can combine with the receptor to elicit a pharmacologic response

  • High affinity and high intrinsic activity/efficacy

Antagonist

  • Drugs that combine with the receptor but do not produce pharmacological response

  • High affinity & low intrinsic activity/efficacy

Types of Drug-Drug Interactions

  1. Pharmacodynamic

    • Addition 1+1=2

    • Synergism 1+6=>2

    • Potentiation 1+0 = 2

    • Antagonism 1+1=0 / negative

Chemical Antagonism

  • Agonist and antagonist will react through a chemical reaction, and the antagonist will counter the effect of the agonist.

  • Beneficial for management of overdose and intoxication

    • Heparin overdose + Protamine Sulfate

    • Heavy Metal poisoning + BAL or dimercaprol + EDTA

      • Ring structure encloses metal making it non-toxic and excreted via urine

    • Opioid overdose + Naloxone

Functional Antagonism

  • 2 Agonist drugs that act independently of each other but have opposite effects that cancel out each other’s effects

    • Acetylcholine + Epinephrine

    • Cardiac Glycosides + Peripheral vasodilator Digoxin inc CO + Hydralazine dec CO

    • Levodopa + Neuroleptics/ Antipsychotics

Competitive/ Reversible Antagonism

  • Antagonist combines with receptor but has no intrinsic activity

  • Displacement Effect

  • Surmountable can be reversed by increasing the concentration of the competing molecule

Non-competitive/ Irreversible Antagonism

  • Antagonist binds to an allosteric site causing conformational change on the receptor inhibiting binding and eventually reducing response

  1. Pharmacokinetic

    • Alters the drug’s:

      • Absorption

      • Distribution

      • Metabolism

      • Excretion

Altered Absorption

  • Transport of drug from the cell membrane to the systemic circulation

  • Rate of absorption is significant in management of HTN, MI, Pain relief, poisoning.

  • Rate of absorption may be compromised for long term therapy as long as Total Drug Absorbed is not affected.

  • Does not occur in IV administered drugs

  • Common in multiple GI preparations administered at the same time or period Most common remedy is adjusting of administration times

    • drug adsorption

Altered Distribution

  • Alters the drug’s:

    • Absorption

    • Distribution

    • Metabolism

    • Excretion

  • Transport of drug from the cell membrane to the systemic circulation

  • Common in multiple GI preparations administered at the same time or period Most common remedy is adjusting of administration times

    • drug adsorption

  • Ion exchange resins (cholestyramine/cholestipol) which lowers cholesterol levels (for hyperlipidemia) has high affinity for bile acids and bile salts forming insoluble complexes which can be excreted in the feces → decreases absorption of other drugs ie. digoxin, warfarin, thyroxine

  • chelation / complex formation

    • Mg+2,Al+3,Ca+2,Fe+2 preparations may interact with tetracyclines, chlorpromazine, and cardiac glycosides by forming complexes

    • Remember to avoid dairy, Ca and Iron supplements and Antacids containing the polyvalent ions.

  • Changes in gastric pH

    • In general, the non-ionized form of the drug is more lipid soluble and readily absorbed into systemic circulation

    • Weak acids → absorbed in low pH

    • Weak bases → absorbed in high pH

    • Ex. Antacid + ASA → ?

  • Changes in gastric motility

    • Ex. Propantheline (IV anticholinergic) + Paracetamol

    • Decreased GER therefore delays absorption of paracetamol where rate of drug absorption is important

    • Tricyclic Antidepressants (TCA) vs dicumarol for OC disorder

    • Imipramine, amitryptiline, clomipramine

    • Imipramine, amitryptiline, clomipramine

  • Problems with transport proteins/ enzymes

    • Problems with transport proteins/ enzymes

    • OCP inhibits the intestinal conjugate enzymes that convert polyglutamic folate to its monoglutamate form leading to folic acid deficiency anemia

Altered Distribution

  • protein-binding

    • Albumin + acidic drugs

    • Glycoprotein + basic drugs

    • Lipoprotein + other drugs

  • Competition for plasma protein sites

  • Protein bound drugs are pharmacologically inactive, only the free or unbound drug can reach the site of action

Displacement of protein bound drugs

  • Depends on concentration and affinity of the drug to protein relative to other drug

  • When a free drug has a higher affinity for the protein, it will displace the other drug.

  • Examples:

    • Warfarin + phenylbutazone → Hemorrhage

    • Chloral hydrate + Warfarin → Hemorrhage

Altered Metabolism

  • Transformation of foreign compounds in the body

  • Drug is made more polar/hydrophilic to facilitate excretion.

  • Facilitated by metabolic enzymes (not substrate specific) found in the skin, liver, and pancreas.

  • Hepatic microsomal P450 oxidases/ Cytochrome P450 Metabolic enzymes in the microsomes of the ER of the liver.

Phase I Reactions

  • Oxidation

  • ReductionBizarre

  • Refers to totally abnormal effects, unrelated from the drug’s known pharmacological actions.

  • Characteristics

    • No formal dose-response curve and very small doses of the drug may elicit the reaction once allergy or idiosyncrasy is established i.e. Penicillin Hypersensitivity – anaphylaxis

    • Reaction disappears on discontinuation of the drug

    • Illness is often recognizable as an immunological reaction

    • Undetectable during conventional testing

    • Little o no relation to the usual pharmacological effects of the drug

    • Delay between first exposure to the drug and the occurrence
      Idiosyncrasy is an example of bizarre reaction

Genetically determined abnormal response to a drug

  • Neuroleptic malignant syndrome

  • Although sometimes dose-dependent, such reactions are unpredictable in most instances.

  • Cannot be sometimes attributed to drug allergy

  • SJS

Genetic Abnormality Drugs Idiosyncratic Response

  • Abnormal hemoglobin Phenacetin Sulphonamides Methemoglobinemia Hemolytic Anemia Erythrocyte G6PD-deficiency Asprin Sulphonamides Vitamin C Hemolytic Anemia Low plasma Activity Procaine Local Anesthetic toxicity

Type B

Bizarre Subdivisions

  • Type Description

  • I IgE-mediated anaphylactic reactions

  • II IgG or IgM mediated cytotoxic reactions

  • III IgG-mediated immune complex reactions

*