Rx Pearls for Medical Students

Drugs for Med Students Presented by Eric Campbell & Jen Chen

Allergy vs Intolerance

• Important to get details early (ie before ICU): – Reaction and specific medication (not just ‘sulfa’)

• Intolerance: side effect of medication – erythromycin, NSAIDS

• Allergy: immune mediated – Anaphylaxis, hives, SJS eg. Penicillin

• Why is this important? – Beta lactam allergy means no pen’s or cef’s and we use

these all the time! – ‘sulfa’ allergy: no Lasix, Celebrex etc

Speaking of Antibiotics

• C Diff … it’s everywhere • Think of this with diarrhea and recent abx. Usually not

bloody, but stool may contain mucous • Another reason not to over prescribe abx • Mechanism: abx knocks out normal flora • Common to have GIT colonization in peds, weird - but even if

diarrhea is present it is likely something else. Check for cdiff toxin or toxigenic C. difficile only if high suspicion (eg high fever, duration >5d, previous abx)

• Any abx can cause, but Clindamycin is esp BAD!

Treatment of C Diff

•Tx: PO Vanco or Metronidazole (if NPO: IV metro +/- intracolonic vanco). Remember, PO vanco is NOT absorbed (which is great for treating a GI infection) and so you do NOT check levels, unlike when you give vanco IV and you DO check levels •If recurrent C diff, fecal transplantation works great!

Prescription Writing 101

Optional:

Pt’s DOB

No Substitution (handwrite only; if you want brandname only or pt requests)

John Smith

123 4th St SW, Calgary, AB

Oct 27, 2014

Amoxicillin 500 mg capsule

Sig: i cap PO TID x 10 days

UF

Quantity: 30

Refills: 0

M. Adams PRACID 283049

First, Do No Harm

• Doctors' sloppy handwriting kills more than 7,000 people annually • Many such errors result from unclear abbreviations and dosage

indications and illegible writing on some of the 3.2 billion prescriptions written in the U.S. every year. – A U.S. study found that as high as 61% of medication errors in

hospitals are caused by illegibly or incorrectly written prescriptions.

• Write generics • Avoid abbreviations of drug names and preparations as these can

be misinterpreted • For PRN dosage, state minimum dose interval and maximum total

amount • No trailing 0’s

• 5 • Not 5.0

• Indicate intentional change on your prescription • Communicate change with your patient

Brand name vs Generic name

Tylenol (acetaminophen)

N-Acetyl-P-Aminophenol

Brand name vs Generic name

Tylenol (acetaminophen)

N-Acetyl-P-Aminophenol

Brand name vs Generic name

Tylenol (acetaminophen)

N-Acetyl-P-Aminophenol

Brand name vs Generic name

• Confusing drug names:

– Pradax(a) vs Plavix

– Both are available in 75 mg in US

– Allegra vs Viagra

– Aripiprazole vs Rabeprazole

– Dobutamine vs Dopamine

– Duloxetine vs Fluoxetine

– Methadone vs Metolazone

• Phone orders

• Be clear

• Mention indication

• Read back

Where can I put it?

Intravenous (iv) Rectal (pr) Via PEG tube

Subcutaneous (sc) Vaginal (pv) Otic

Intramuscular (im) Transdermal (patch) Ophthalmic

Oral (po) Topical (top) Buccal

Sublingual (sl) Intrathecal Intracavernous

Inhalational (puff/neb) Intraarticular Intravesical

Nasal Via NG tube Intrauterine

SL, PR (2/3 bypassed), IV, IM, inhalation, transdermal – avoid first pass effect!

Increase drug bioavailability

Psych (IM for depot action) or noncompliant patients

NPO patients, dysphagia

Keep volume low for SC and IM

What does it all mean?

ac Before meal PRN As needed

cc With meal UD Use as directed

pc After meal HS At bedtime

OS Left eye QD, OD Once daily

OD Right eye BID Twice daily

OU Both eyes TID 3x/day

gtt Drop QID 4x/day

supp Suppository BIDAC Twice daily before meals

NPO Nothing by mouth TIDCC 3x/day with meals

ungt Ointment QAM Every morning

UF Until finished Q4-6H PRN Every 4 to 6 hours as needed

Tbsp Tablespoon (15mL) Tsp Teaspoon (5mL)

i, ii, iii 1, 2, 3 (tablet, capsule, application, etc)

What does it all mean?

ac Before meal PRN As needed

cc With meal UD Use as directed

pc After meal HS At bedtime

OS Left eye QD, OD Once daily

OD Right eye BID Twice daily

OU Both eyes TID 3x/day

gtt Drop QID 4x/day

supp Suppository BIDAC Twice daily before meals

NPO Nothing by mouth TIDCC 3x/day with meals

ungt Ointment QAM Every morning

UF Until finished Q4-6H PRN Every 4 to 6 hours as needed

Tbsp Tablespoon (15mL) Tsp Teaspoon (5mL)

i, ii, iii 1, 2, 3 (tablet, capsule, application, etc)

Best to write out exact volumes to prevent error. Parents may use spoons at home to give an inaccurate amount causing over- or under-dosing. Pharmacy will provide measuring spoons.

IV Compatibility

• Usually nurses will sort this out and will contact pharmacy directly, however you may be asked

• Concern is re precipitation of drugs

• Who to ask? Pharmacists have a lot of resources!

• Where to check? Lexi-comp (this is accessible through UpToDate), Micromedex, Trissels

Special dosing • Renal: most new drugs have this information in their

monographs (look at Lexi-comp, Uptodate). When in doubt, look it up!

• Hepatic: trickier, Child-Pugh score? • Geriatric: trickiest? Usually based on liver and kidney

function which decline with age. – Also consider kinetics: may have variable absorption, smaller (or

larger) Vd, altered protein binding, reduced metabolism and elimination.

– High risk meds: Beers criteria (old), STOPP criteria (new)

• Pediatric – weight-based dosing • Pregnancy: MotherRisk: great resource! • Lactation: Lexi-comp, Drugs In Pregnancy & Lactation

Drug Coverage

• What is “covered” and what does that mean? – Provincial plans (Alberta Blue Cross): seniors, Alberta

Works, AISH – National Plans: NIHB, IFH – Private insurance – Hospital Formulary – Special situations: TB, HIV, Chemotherapy, Palliative

• Why is this important? – $$$ -> Patient compliance? – Not all formularies are the same, not all drugs are on all

formularies – However you do it (call pharmacy, social work) make sure

the patient can access the drug before they leave

Special Authorization

• This is specific to Blue Cross (usually) – Provincial plans

• Certain criteria need to be met, and the form needs to be filled out by the MD

• Pharmacy will call you, but it’s really helpful if you know some of the common drugs that need this (don’t worry, you will)

• Coverage usually is for 12-24 months then need to repeat application

Example Special Authorization

• Cholinesterase inhibitors (remember course V?): Need MMSE 10-26

• Most the anticholinergics for OAB: need to try oxybutynin first

• Bisphosphonates: need to try Didrocal (etidronate) first • New oral anticoagulants, aren’t they great? Need to try

warfarin first (unless contraindicated) • How will I remember all these? www.idbl.ab.bluecross.ca

Schedules & Controlled Substances

• This is a big topic but here are some quick tips: • If the drug makes you feel kinda funny, there’s

probably a restriction on it, usually to do with refills: – Narcotics (morphine, hydromorphone, oxycodone etc): NO

REFILLS – Benzodiazepines (Valium – diazepam, and cousins such as

lorazepam, clonazepam): refills allowed but need to specify intervals. But if you’re using them long term the patient should probably just see you regularly

• Part fill: if you really want to, you can do this – Eg Morphine 10mg PO BID #180 tabs, dispense 60 tabs

every 30 days

Triplicates

• Alberta’s provincial program to monitor highly abused drugs.

• Drug list: changes, eg Morphine, Hydromorphone, Oxycodone, Methadone, Fentanyl.

• Benzodiazepines are also being monitored (starting Fall 2015) though they do not require triplicate Rx.

• One copy you keep – two go with the

patient to bring to Pharmacy

•Pharmacy then keeps one, sends the

other to CPSA

• IMPORTANT! Must fill within 72 hours!

• IMPORTANT! Keep your triplicate pads secured! Report ASAP if stolen or missing.

Drugs in Pregnancy & Lactation

• Every woman has a 3–5% risk of having a child with a birth defect or mental retardation.

• Birth defects are the leading cause of infant mortality in the US.

• 2 important factors to consider when assessing the teratogenic potential of a medication

–Stage of pregnancy at which the exposure occurred

–Amount of medication taken.

• It is critical to evaluate each exposure on a case-by-case basis.

Drugs in Pregnancy & Lactation

• If you have a pregnant or breast feeding patient who is currently taking, or considering taking, a medication, the patient needs to be counseled about potential adverse effects the medication could have on her fetus or infant.

• Counseling needs to be documented in the patient’s chart.

Drug Ratings in Pregnancy (FDA) Category Interpretation Example

A Controlled human studies show no risk Controlled studies in pregnant women fail to demonstrate a risk to the fetus in the first trimester with no evidence of risk in later trimesters. The possibility of fetal harm appears remote.

Thiamine, diclectin

B No evidence of risk in studies Either animal reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women, or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester and there is no evidence of a risk in later trimesters.

Cephalexin, amoxicillin, pantoprazole, ranitidine

C Risk cannot be ruled out Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal effects or other) and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefits justify the potential risk to the fetus.

Lamotrigine, levetiracetam, ciprofloxacin, acetaminophen, ibuprofen (C/D ≥30 weeks gestation)

D Positive evidence of risk There is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (eg, if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).

Phenytoin, carbamazepine, tetracycline, ramipril, ibuprofen (C/D ≥30 weeks gestation)

X Contraindicated in pregnancy Studies in animals or human beings have demonstrated fetal abnormalities or there is evidence of fetal risk based on human experience, or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Valproic acid, warfarin, atorvastatin, isotretinoin, thalidomide, methotrexate

Important Teratogens to Remember

• ACE-inhibitors

• Statins

• Warfarin

• Vitamin A derivatives / tretinoins (eg. Accutane)

• Methotrexate

• Valproic acid

• Thalidomide

• Always double check!

Drugs in Lactation

• The amount of drug excreted into milk depends on a number of factors:

– More lipid soluble

– Smaller molecular size

– Weakly basic drugs

– Plasma pH 7.4

– Breast milk pH 7.2

– Higher blood level in maternal circulation

– Lower protein binding in maternal circulation

– vs. higher protein-bound drugs like warfarin, which are excreted into the

breast milk in low amounts and reduces

infant’s exposure

– Oral bioavailability

– Frequency of feeding

– Volume of breast milk

– Long half life

Drugs in Lactation

• Drugs usually contraindicated while BF: –Antineoplastics and immunosuppressants –Lithium Carbonate –Gold –Iodine –Radiopharmaceuticals –Social drugs and drugs of abuse

• Cautions: –Antipsychotics, antidepressants, benzodiazepines –Opioids (yes, even Codeine) –Antibiotics –Antithrombotics

• Always double check!

Resources

• Uptodate • DynaMed • Pregnancy and Lactation • Motherisk.org • LactMed

• Rx Files

• Pharmacists

• PADIS 1-800-332-1414

Interesting Drug Fact

• Penicillin was discovered from mold dropping into a petri dish (1928)

Interesting Drug Fact

• Viagra (sildenafil) was and still is used to treat pulmonary hypertension. A happy side effect resulted in a different marketing strategy.

Interesting Drug Fact

• Thalidomide, a drug that caused devastating fetal abnormalities is currently being studied for its anti tumor effects. The same actions that impaired fetal limb growth (reduced angiogenesis), make it especially effective in reducing the growth of tumors.

Interesting Drug Fact

All natural ...

• Exenatide, a glucagon like peptide (GLP-1) agonist used to treat Type II

Diabetes is found in the saliva of the Gila monsters.

• Premarin (conjugated estrogens): PREgnant, MARe, urINe

• Hirudin, an anticoagulant (direct thrombin inhibitor) found in the saliva of

the medicinal leech Hirudo medicinalis

Interesting Drug Fact

• Chlorpromazine, an old antipsychotic, was being studied in psychiatric patients to assess safety prior to being marketed as an antinauseant. Surprisingly, symptoms of schizophrenia improved dramatically.

Interesting Drug Fact

• Cocaine is used to treat nosebleeds (potent vasoconstrictor).

• It can also cause perforation of nasal septum in long term cocaine users.

Interesting Drug Fact

• Half life matters: – Nitro infusion 1-4 minutes (great for titrating to effect) – Vitamin D tablets (long elimination half life due to large

volume of distribution - can take weekly or even monthly)

Pharmacists

• 33,000 licensed pharmacists in Canada

– 24,000 work in 8,600 community pharmacies

– 5,600 work in hospitals

– Pharmaceutical industry

– Governments

• Primary Care Network

• Alberta Blue Cross

• PADIS

– Colleges and universities and associations

How to Become a Pharmacist

• A bachelor's or doctor of pharmacy degree from 1 of 10 Canadian universities

• To complete a national board examination through the Pharmacy Examining Board of Canada (PEBC) (with the exception of Québec)

• Practical experience through an apprenticeship/internship program

• Fluency in English or French • Optional: 1-year pharmacy residency, 2-year post-graduate

Doctor of Pharmacy degree

Role of Pharmacists • Dispensary

– Drug interactions – Drug information – Dosage adjustments – Chemotherapy – Therapeutic drug monitoring (vancomycin, phenytoin,

valproic acid, lithium, digoxin, carbmazepine, theophylline, gentamicin)

• Immunization • Chronic disease management • Medication review & counseling • Extending refills • Specialized areas: diabetes, asthma, COPD, menopause,

breastfeeding, travel clinic, PADIS • Some have additional prescribing privileges