Transcript Troubleshooting the Antibiotic Prescription

Troubleshooting the
Antibiotic Prescription
Dr. LA Sulz (BSP, PharmD)
Pharmacists’ Association of Saskatchewan Annual Conference
Regina, Sask.
April 26, 2015
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Presentation Overview
Why it’s important to optimize use of
antimicrobials
Optimize antimicrobial use to ensure efficacy
while minimizing resistance development in
common community-acquired infections
Identify management strategies to prevent,
or minimize clinically significant drug
interactions with common antimicrobials
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Consequences of
Antimicrobial Resistance
 At least 2 million Americans fall ill from antibiotic-resistant
bacteria every year; at least 23,000 die (CDC Sept 2013)
 1/9 patients admitted to hospital each year (250,000
Canadians) develop hospital acquired infections; 8,000 die
(Health Canada)
 Greater than the number of fatalities from traffic accidents, AIDS
and breast cancer combined
 Many are resistant to available antibiotics
 Compounding the problem, infections are acquired in other
health care settings, such as LTCFs & increasingly the
community at large
http://www.cihr-irs .gc.ca/e/40485.html accessed Oct 20/13
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Contributors to Antimicrobial
Resistance
 Unnecessary antibiotic use
11 million kilograms prescribed/year in the U.S.
1.1 million kg (Canada)
75% for respiratory tract infections  over 30% not
needed
More than $1.1 billion spent annually on unnecessary
prescriptions for adult respiratory infections (U.S.)
$110 million (Canada)
 Improper use (e.g. too long, wrong dose)
 Lack of rapid diagnostics
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Antimicrobial Resistance
 Antibiotics promote resistance by killing susceptible
organisms so resistant organisms have a survival
advantage and can be passed on to other people
 Studies of changing prescribing patterns to improve
resistance patterns has been shown in the community
setting in regards to S. pneumoniae resistance
 Resistance patterns do not always respond to
prescribing changes
 Proactive approach is best – i.e. Use antimicrobials only
when indicated
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Combating Antimicrobial Resistance
Shorter Duration - Longer not necessarily
better!
Community-acquired pneumonia (CAP) 3d vs 8d
Cellulitis 5d vs 10d
Cystitis 3d vs 7 – 10d
Acute pyelonephritis 7d vs 14d
Higher doses - Generally safe (with
exceptions)
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Antibiotics carry other risks!
 1 in 4 chance of diarrhea...
 1 in 50 chance of a skin reaction...
 1 in 1000 chance of an ER visit . .
For comparison, 2 out of 1000 patients will go to the Emergency
due to ADR associated with warfarin, insulin, or digoxin
Risk of an ED visit due to an antibiotic (80% due to allergic
reactions) is 3X higher than the risk due to antiplatelet agents
(e.g., aspirin), oral hypoglycemic agents (e.g., glyburide), and
narrow therapeutic window drugs (e.g., anticonvulsants)
Shehab N et al. Clin Infect Dis 2008;47:735-43.
Canadian Pharmacist's Letter; April 2012; Vol: 19
 1 in 5000 will have an anaphylactic reaction
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Clostridium difficile Infection
 Most frequent cause of healthcare-associated
infectious diarrhea in Canadian hospitals
 Most common cause of acute infectious diarrheal
illness in LTCFs
 Strongly associated with previous antibiotic use
 Antimicrobial stewardship believed to have a role
in preventing and terminating C. difficile infection
outbreaks
http://www.phac-aspc.gc.ca/nois-sinp/guide/c-dif-ltc-sld/index-eng.php
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Antibiotics & Risk of C. difficile Infection
 Largest risk compared to no antibiotics
 Clindamycin - OR 16.8 (7.5 - 37.8)
 Fluoroquinolones - OR 5.5 (4.3 - 7.1)
 Cephalosporins, carbapenems - OR 5.7 (2.1 - 15.2)
 Lower association with
 Macrolides - OR 2.6 (1.9 - 3.6)
 Penicillins -OR 2.7(1.8 - 4.2)
 Sulfonamides/Trimethoprim - OR 1.8 (1.3 - 2.4)
 No effect noted with tetracyclines - OR 0.9 (0.6 - 1.4)
Antimicrobial Agents and Chemotherapy 2013 (57; 5): 2326–32
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Additional cause for concern:
Dwindling antibiotic pipeline
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Now, let’s troubleshoot a
few cases to see if we can
be ‘Antimicrobial Stewards’
to preserve effectiveness of
our current antibiotics. . . .
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Case
Patient arrives with a Rx for cephalexin
What’s the first thing you do?
What might you ask the patient?
What’s the antibiotic for?
Patient replies, “I was cleaning up the backyard
and cut my finger on something a couple days
ago, and now it’s red, painful and swollen. I think
it’s infected.”
What are the most likely causes of skin & soft
tissue infections?
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Diagnosis – Skin & Soft Tissue Infections
(SSTIs)
Diagnosis & empirical therapy based on
physical findings and clinical setting
Rarely obtain C&S
Most cutaneous infections not associated
with bacteremia
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Prevention - SSTIs
 Good hygienic practices; attention to early therapy
for superficial processes such as dermatophyte
infection
 Reduces risk for cutaneous & soft tissue infection
 Individuals with recurrent cellulitis may benefit from
chronic antibiotic suppression
 3–4 episodes/year despite attempts to treat or control
predisposing factors (weak, moderate)
e.g. oral penicillin , erythromycin b.i.d. for 4–52 weeks, or IM
benzathine penicillin q2–4wks
 Continued as long as predisposing factors persist (strong,
moderate)
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Common Community SSTIs
 Impetigo
 A superficial crusting, and at times, bullous infection of the skin
 Localized progression into the dermis leads to ecthyma  crusting skin
infection caused by pyogenic streptococci, similar to impetigo, but
extends more fully into the epidermis
 Folliculitis
 A localized infection of hair follicles, which can extend into
subcutaneous tissue, resulting in furuncles
 May coalesce, leading to carbuncle formation which are typically
larger and deeper than furuncles
 Most commonly on the back of the neck, especially in individuals with diabetes
 Furuncles often rupture and drain spontaneously or following treatment
with moist heat
 Most large furuncles, all carbuncles should be treated with incision
and drainage
 Systemic antimicrobials usually unnecessary, unless fever or other
evidence of systemic
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Case – Cellulitis
 Vast majority from streptococci, often group A (GAS, S.
pyogenes), but also from groups B, C, F, or G
 Staphylococcus aureus less frequently causes cellulitis
 associated with open wound, previous penetrating trauma,
including sites of illicit drug injection
 What are the antibiotic options?
 Cloxacillin?
 Covers Staph > Strep
 Staph more likely if abscess/pus
 No need for renal dose adjustment
 TMP-SMX?
 No !  Poor GAS coverage
 Suitable antibiotics for most include:
 Penicillin, Amoxicillin, Cloxacillin, Cephalexin, Clindamycin
 5 days as effective as10 days if clinical improvement by day 5
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10 Point Antimicrobial Checklist
1.
2.
3.
4.
5.
6.
7.
8.
9.
Is an antibiotic indicated?  preventative, empiric, directive
Have appropriate specimens been obtained, examined, and
cultured?
What organisms are most likely?
Which antibiotic is best?
Is combination therapy required?
What are the important host factors?
What is the best route of administration?
What is the appropriate dose?
Will initial therapy require modification?
 Consider narrowest spectrum agent; review PK/PD, toxicology, cost,
spectrum, and whether important to be bactericidal vs bacteriostatic
10. What is the appropriate duration of therapy?
 Is resistance going to be a problem?
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5 – Point Antimicrobial Checklist
1.
2.
3.
4.
5.
Is an antibiotic indicated?

Preventative, empiric, or directive?

Most likely organism(s)?


Is combination therapy required?
What is the appropriate duration of therapy?

Allergies, renal function, immune status, elderly, debilitated,
etc.
What is the appropriate dose?
Appropriate specimens obtained?
Which antibiotic is best?
Are there important host factors present?

Will therapy require modification?
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
Another case to
troubleshoot . . .
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Case
Patient comes into your Pharmacy with a
Rx for amoxicillin
He indicates having a very sore throat
with very painful swallowing and trouble
eating
How do you proceed?
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Case
What’s the likely indication?
”strep throat”?
How might you confirm this?
1. Is an antibiotic indicated?
2. Appropriate specimens obtained?
Ask if throat swab done; if so, check e-health
 if negative, NO antibiotic indicated
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Case - Upper Respiratory Tract Infection
(Acute pharyngitis, “Strep throat”)
Upper RTIs more common than lower RTIs
(bronchitis > pneumonia), and . . .
Primarily due to viruses ! !
Large majority self-limiting
Supportive care only  offer appropriate
doses of analgesics, antipyretics
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Case – Diagnosis of Acute Pharyngitis
Presence of 4 centor criteria:
History of fever
Tonsillar exudates
No cough
Tender anterior cervical lymphadenopathy
(lymphadenitis)
Do not treat if none, or only 1 criteria
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Case – Diagnosis Acute Pharyngitis
3. Which antibiotic is best?
What organisms are most likely?
After viruses, most common bacterial cause is Group
A beta hemolytic streptococcus (GABHS)
Limit antibiotics to those with the highest likelihood of
GABHS (4 centor criteria)
 GABHS is 100% susceptible to penicillin
 85% to clindamycin, erythromycin -- local (RQHR)
antibiogram
 Cephalexin (1st gen ceph) if not anaphylactic allergy to
penicillin
 Macrolide (erythro, clarithro, azithromycin) if true penicillin
allergy
 Fluoroquinolone or other broad spectrum agent
(amox/clav) NOT required
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Case – Diagnosis Acute Pharyngitis
4. What are the important host factors?
?Immune status, corticosteroid use, elderly . . . .
?Renal function (check e-GFR)
Pen V 300mg po QID
Pt has Rx for amoxicillin which would be acceptable
Usually x10 days (5 days if azithromycin)
5. Will initial therapy require modification?
 If GABHS  Symptoms improve dramatically
within 1 - 2days! (If not, unlikely bacterial)
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What if another patient comes in
with Rx for amoxicillin. . .
But, it’s for a ‘ head cold’, runny nose
He sounds like he has nasal congestion and says
he coughs, especially at night
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URTI  Rhinosinusitis/Acute Bacterial Sinusitis
 Common problem with 1 / 7 U.S. adults each year1,2
 Translates to  2.6 million cases in Canada yearly3
 Acute bacterial sinusitis 200 times less common than viral
 Resolves without antibiotics in majority of cases
 Symptoms less than 7 days - unlikely to have a bacterial infection
 Consider antibiotics if:
 Persistent signs/symptoms for 10 days without any evidence of clinical
improvement, or severe symptoms such as fever of 39ºC or higher plus
 Purulent nasal discharge, maxillary facial/tooth pain, swelling, or tenderness for 3
to 4 days (when unilateral regardless of duration of illness or facial pain)
 If cold symptoms for 5 to 6 days, got better, now worse
1.
2.
3.
Chow AW, et. al. IDSA guideline Clin Infect Dis 2012;54:e72-e112.
Rosenfeld RM. Clinical practice guideline on adult sinusitis. Otolaryngol Head Neck Surg 2007;137:365-77.
Desrosiers M, et al. Canadian clinical practice guidelines. J Otolaryngol Head Neck Surg 2011;40(Suppl
2):S99-193.
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Rhinosinusitis/Acute Bacterial Sinusitis
 All patients, supportive measures...fluids,
analgesics (ibuprofen, etc), nasal irrigation
 If it is bacterial  S. pneumoniae, H. influenzae
 Amoxicillin/clavulanate for empiric tx adults &
children
RQHR antibiogram: 40% H. influenzae resistant to
amoxicillin alone
Reminder: If using high doses for intermediate resistant
S. pneumonaie, must combine with amoxicillin to not
‘overdose’ clavulanate causing significant diarrhea
 So, amoxicillin, not an optimal choice in this case
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Bronchitis -‘Acute Cough Illness’
 Greater than 90% Non-bacterial
 Coughs associated with bronchitis often prolonged:
 45% will have a cough at 2 weeks
 25% still have a cough at 3 weeks
 In patients with cough more 3 weeks, CXR warranted
in the absence of other known causes
 FYI - OTC cough suppressants have limited efficacy in relief
of cough due to acute bronchitis (Chest 2006; 129:95S103S)
 Routine antibiotic treatment of uncomplicated
bronchitis NOT recommended, regardless of duration
of cough
cdc.gov/getsmart/campaign-materials
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Community-Acquired Pneumonia (CAP)
 Uncommon in healthy, non-elderly adults in absence
of vital sign abnormalities, or asymmetrical lung
sounds
 S. pneumoniae accounts for up to 50% of CAP caused
by bacteria
 Choice of treatment?
 Doxycycline (S. pneumoniae + atypicals)
 Clarithromycin/Azithromycin  susceptibility S. pneumoniae
 2nd generation cephalsporin  cefprozil, cefuroxime
though atypicals not covered
 Reserve FQs for more severe illness, or pts allergic to
alternatives
Always AVOID ciprofloxacin as poor gram positive coverage
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Acute Excerbation COPD
 Etiology – S. pneumoniae, H. influenzae, M. catarrhalis
 NOTE: Don’t require atypical coverage as for CAP so
levofloxacin or moxifloxacin not required
 Empiric Tx?
 Amoxicillin/clavulanate, 2nd gen ceph (cefprozil,
cefuroxime)
 Clarithromycin/Azithromycin if true beta-lactam allergy
 5 - 7 days usually adequate
Cannot eradicate the bacteria due to damaged lung structure
Longer duration only promotes resistance
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
What about the patient who says. .
. . . “I’m allergic to penicillin”
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Penicillin Allergic Patients
 10 - 15% hospitalized patients report a penicillin allergy
 Recent literature suggests up to 95% are negative
 Must I avoid a cephalosporin?
 What’s the likelihood of a cross reaction?
 1 in 500 (0.2%) patients with non-severe reactions to penicillins
 Negligible if -ve penicillin skin test
 2 in100 (2%) patients who have a positive penicillin skin test will
have an IgE-mediated response
 Anaphylaxis is rare  1 - 4 per 10,000 administrations
 Take a thorough history and enter into computer system for
future reference
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Penicillin/Cephalosporin Cross-Reactivity
 Patients who’ve reacted to penicillin; skin testing not
available
 Low risk if penicillin reaction >10y ago and/or not IgEmediated reaction (anaphylaxis, urticaria, angioedema,
hypotension, bronchospasm, laryngeal edema, pruritis)
Give cephalosporin
 Moderate risk if reaction <10 years and/or IgE mediated
reaction
Give cephalosporin by graded challenge  start 1/100
cephalosporin full dose, with ten-fold increasing doses q30-60 minutes
until full dose
Reaction within 24h may occur in less than 1%, but risk of anaphylaxis
is small
 High risk if probable anaphylaxis to penicillin based on history
Desensitize to cephalosporin
UpToDate (Sept 30/14)
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IgE Mediated Reactions
Type I reactions can be life-threatening
Immediate: within 30-60 minutes
Delayed: within 1-72 hours
Clinical features  pruritis, flushing, urticaria,
wheezing, angioedema, hypotension
Symptoms typically appear within four hours
Urticaria associated with raised red intensely
pruritic plaques
Anaphylaxis (most severe form) is rare
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Next case . . .
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Case
Patient comes into your Pharmacy with a
Rx for ciprofloxaxin
What are your next steps?
?Indication
UTI?
Causative organism(s)? . . etc, etc.
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5 – Point Antimicrobial Checklist
1. Is an antibiotic indicated?
 Preventative, empiric, or directive?
2. Appropriate specimens obtained?
 Most likely organism(s)?
3. Which antibiotic(s)?
 Appropriate duration?
4. Important host factors present?
 Allergies, renal function, immune status, elderly,
debilitated, etc.
 Appropriate dose?
5. Therapy modification? – i.e. Monitoring req’d
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Urinary Tract Infections (UTIs)
Incidence, including urethritis, cystitis,
prostatitis, & pyelonephritis
8 - 10 million/year in U.S.
20% (1/5) women symptomatic UTI in lifetime
Many with multiple recurrences (30%)
Men much less until 65yo
 20-30% of infections reported by longterm care facilities (LTCFs)
cdc.gov/nhsn/PDFs/LTC/LTCF-UTI-protocol_FINAL_8-24-2012.pdf
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Landry e et al. Urinary Tract
Infections: Leading Initiatives in
Selecting Empiric Outpatient
Treatment (UTILISE)
CJHP Mar–Apr 2014
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UTIs First Line Therapy
– No EDS/Inexpensive
 Nitrofurantoin (Macrobid) 100mg po bid x 5-7d:
Rule out systemic infection – i.e. upper UTI,
pyelonephritis, bacteremia  limitied/low tissue
penetration
Check renal function Avoid if Clcr <60mL/min
 TMP-SMX 1 DS tablet po q12h
If Clcr 15-30mL/min: 1 SS tablet PO q12h
 Clcr <15mL/min - Avoid
If sulfa allergy  Trimethoprim 100mg po q12h
Possible hyperkalemia if ACEI, ARB, or K+ supplements
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Second Line Therapy – EDS Required
 Amoxicillin/Clavulanate (875mg/125mg po q12h, or
500mg/125mg q8h) unless:
 True penicillin allergy  Anaphylaxis: hives, SOB, throat swelling
 Known resistant organism (i.e. Pseudomonas on C&S result)
 Cefprozil, Cefuroxime (2nd gen cephs) 250mg po q12h
(500mg if upper UTI) unless:
 Severe penicillin allergy  Anaphylaxis: hives, SOB, throat
swelling or, cephalosporin allergy
 Known resistant organism  Check C&S result
 Beta-lactams (cephalexin, amoxicillin) may be less effective
for UTIs
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Last Resort – EDS Required & Resistant
Organisms
Ciprofloxacin 250mg po q12h (500mg if
upper UTI) only if:
Sulfa and severe beta-lactam allergy
Known resistance to all above agents (i.e.
Pseudomonas)
Duration?
3 days effective for most; may need longer in
elderly due to physiological issues (e.g. prolapsed
uterus, prostatitis)
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Case - UTI
 What if when you check a recent e-health record, it
indicates urine C&S result as:
 E. coli resistant to cephalexin, ceftriaxone, ciprofloxacin,
TMP-SMX; only susceptible to gentamicin/tobramycin
 ESBLs (e.g. E. coli, K. pneumonaie resistant to many broad spectrum
agents such as 3rd gen cephs and ciprofloxacin & other FQs)
 Often leaves only aminoglycosides, or broad spectrum parenteral
agents
 How did this patient get such a resistant organism?
 ?Multiple courses of antibiotics
 ?Long-term urinary catheter
 What do you do?
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Case - UTI
 Consider Fosfomycin 3g po x1 dose
Symptoms take longer than a day to disappear
Avoid if pyelonephritis suspected
 What if no C&S result, but a urinalysis report
indicates:
+ve Leukocytes
-ve Nitrates
Bacteria: Scant
 If both leukocyte & nitrate test +ve, higher
likelihood of bacterial infection, but should
confirm with C&S
If NO symptoms, Don’t treat!
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Case
You receive a fax for ciprofloxacin for a
resident in the LTCF for which you provide
service
What do you do?
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5 – Point Antimicrobial Checklist
1.
2.
3.
4.
5.
Is an antibiotic indicated?


Preventative, empiric, or directive?
Symptoms?

Most likely organism(s)?


Appropriate duration?
Check e-health records





Allergies, renal function, immune status, elderly, debilitated, etc.
?catheterized; how long?
Appropriate dose?
Check renal clearance  Be wary if estimated clearance in elderly or debilitated pt
is >80mL/min as calculation is based on creatinine which may be low in those with
low muscle mass
If wt unknown  estimate Clcr = (140-age)x 90/Scr (x 0.85 if female)

FYI – No need for repeat C&S to confirm eradication (except in pregnancy)
Appropriate specimens obtained?
Which antibiotic(s)?
Important host factors present?
Therapy modification? – i.e. Monitor pt for symptom resolution
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Asymptomatic bacteriuria
 Significant bacteriuria (>108/L), but absence of symptoms
 Common, particularly if 65yo or older
 Chronically catheterized patients
 After 10 - 14days, urine will be smelly, cloudy AND always be +ve
 If no symptoms, do not treat
 If symptoms present, catheter must be removed, or symptoms
will return after discontinuation
 Treatment depends on clinical setting
 Usually treat significant bacteriuria (>108 CFU/L) without pyuria
(<10 WBCs) in infants & preschool children
 ?anatomical or mechanical defects
 ?renal tissue damage during growth phase
 May develop pyelonephritis, if confirmed on successive cultures
 Bacteriuria persisting 48h after catheter removal
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Recurrent UTIs
 Recurrent Symptoms/Relapse
 Recurrence within 1 - 2 weeks after treatment; usually same
organisms  Retreat with previous agent for longer duration
 e.g. If used a 3 day regimen, retreat for 7 days; if was 7 day regimen,
retreat for 14 days
  25% of women
 At least 2 episodes within 6 months, or 3 or more +ve urine
cultures within 12 months
 Before starting prophylactic antibiotics, urine C&S 1-2 weeks
after infection to rule out relapse
 Continuous prophylaxis usually given at bedtime
 May give every other night or three nights a week
 Continue prophylaxis for about 6 to 12 months... up to 5 years in
difficult cases
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Recurrent UTIs
 Continuous or post-coital prophylaxis
 Nitrofurantoin 50 mg, or cephalexin 250 mg for women who usually get UTIs
24 - 48h after intercourse
 Take single antibiotic dose after intercourse
 Avoid contraceptives with spermicide  can cause local
irritation and increase chance of bacterial growth
 Acute self-treatment for women you trust to understand and
follow the instructions
 i.e. When they get symptoms, drop off a urine sample at the lab
for culture and start a 3-day course of antibiotics
 If symptoms are not gone within 48 hours, change to a different
antibiotic
 Choose an antibiotic for UTI prophylaxis based on tolerance,
resistance patterns, and cost. . . they usually have similar
outcomes
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Recurrent UTIs
Don't recommend probiotics...there's no
proof they help prevent UTIs
Don’t use prophylaxis if urologic
abnormalities or in asymptomatic elderly
Contributes to resistance
Canadian Prescriber's Letter; February 2011; Vol: 18
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Treatment for UTIs
 Cranberry juice?
 Doesn't TREAT a UTI...but may help PREVENT recurrent infections
 Duration
IDSA. 2011 Guideline (Women) - Clinical Practice Guidelines CID 2011:52 (1 March)
Canadian Prescriber's Letter; April 2011; Vol: 18
Epp A, et Al. J Obstet Gynaecol Can 2010;32:1082-90
 3 - 5 days for uncomplicated UTIs
 7 - 14 days for complicated UTIs
 Many elderly patients due to anatomic abnormalities
 6 - 12 weeks for men with prostate involvement
 Don't screen for, or treat asymptomatic bacteriuria -- There's
no benefit...and it increases resistance
Canadian Prescriber's Letter; December 2011; Vol: 18
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Limit use of FQs for UTIs – Why??
Moxifloxacin doesn't get into the urine
 Increasing gram –ve resistance
 RQHR 15% E. coli resistant to cipro
Ciprofloxacin usually works, but can cause
"collateral damage“ by inducing resistant Staph,
Pseudomonas, Enterococcus, etc.
FQs associated with  C. difficile, MRSA
outbreaks & increasing resistant E. coli
Canadian Prescriber's Letter; April 2011; Vol: 18
Epp A, et. Al. J Obstet Gynaecol Can 2010;32:1082-90
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Let’s troubleshoot this last case . . . .
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Case
 64 yo female presents at your Pharmacy with a Rx for moxifloxacin
 A review of her medication profile includes the following:
 Tiotropium (Spiriva), fluticasone inhaler, salbutamol inhaler for COPD,
and warfarin for stroke prevention d/t Afib
 What are the possible antibiotic-related problems?
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Case
 Aug 1 – INR 1.8
Missed a dose previous week, so cont’d same dose
(80mg/wk) with 13mg x1
 Aug 8 – INR 1.9
14mg x1, incr 84mg/wk – 12mg/d
 Aug 22/13 (Thurs) - INR = 7.2
Aug 17/13, 4 days prior, Rx moxifloxacin x 14 days +
prednisone for AECOPD
Informed pt to hold x 3d (Th, F, Sa) & reume warf
Sunday at reduced dose 10mg/d (70mg/wk = 17%);
repeat INR on Monday, Au 26
 Aug 26 - INR 1.0
Pt held warfarin all 4 days (Th – Sun)
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
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Case
 47yo female with PE discharged from hospital on stabilized
dose of warfarin 10mg/day
 Sept 4 INR 3.1
 Sept 12 = 2.7
 Sept 20 = 5.4 – started herbal med to help thin the blood-advised AGAINST this, but pt refused. No bleeding
 Hold 2 doses, decrease warfarin to 5mg/d x 2 days & repeat INR
 Sept 24 INR 1.3 (0, 0, 5, 5) – no identified changes; pt refused
LMWH; increased back to warfarin 11mg/d
 Sept 26 INR = 6.4 (after 2 doses 11mg); will stop herbal med –
No warfarin today
 Sept 27 INR 7.9 – i.e. cont to rise after 1 held dose
 What are your thoughts?
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Case
Checked PIP  Septra DS x7d Sept 20-26
for UTI 6 days prior to elevated INR
Hold x2days and start wafarin 5mg/d
In the meantime very low INRs and pt
back on 11mg/d
Oct 31 INR = 5.5 – Septra Rx start 30
(again!)
Patient counselling is imperative!
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Drug Interactions - Significant
 Patients on warfarin  Suggest alternative antibiotics (e.g.
amox/clav, cephalosporins)
 May need EDS, but safer, more convenient than increased INR
monitoring, dose adjusting when starting & stopping antibiotics
 Suggestions for empirically  warfarin:
 SMX-TMP: 25 - 40%
 Metronidazole: 25 - 40%
 Miconazole, Fluconazole, Voriconazole: 25 - 30%
 Clarithromycin: 15 – 25%
 Moxifloxacin: 0 – 25%
 Erythromycin: 10 - 15%
 Ciprofloxacin: 10 – 15%
 Levofloxacin: 0 – 15%
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
Bungard, T, Brockelbank, C, CPJ
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Miscellaneous Tips
Antimicrobial Therapy
 Antibiotics are not innocuous  Serious, long-term lifealtering reactions (e.g. CDAD)
 Do NOT dose cephalexin, cloxacillin, penicillin V b.i.d.
 Very short half lives; kills bacteria in TIME-dependent, not
concentration-dependent manner
 So why do patients get better?
 Infection likely due to a virus, not bacteria!
 Suboptimal doses may contribute to development of
resistance
 Cost/EDS
 Remember to remind patients, EDS does not mean free
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Sometimes the best thing you can do
for a patient is NOT fill their antibiotic
Rx!
Remember: Most upper respiratory infections are
due to viruses!
Use the antibiotic check list for a systematic
approach
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5 – Point Antimicrobial Checklist
1.
2.
3.
4.
5.
Is an antibiotic indicated?


Preventative, empiric, or directive?
Symptoms present?

Most likely organism(s)?



Check e-health records for recent C&S results
RQHR: Contact Med Microbiologist for assistance in interpretation
Appropriate duration?




Allergies, renal function, immune status, elderly, debilitated, etc.
?catheterized; how long?
Appropriate dose?
Check renal clearance  Be wary if estimated clearance in elderly or debilitated pt
is >80mL/min as calculation is based on creatinine which may be low in those with
low muscle mass
If wt unknown  estimate Clcr = (140-age)x 90/Scr (x 0.85 if female)
Appropriate specimens obtained?
Which antibiotic(s)?
Important host factors present?

Therapy modification? – i.e. Monitor pt for symptom resolution
Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)
Questions?
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Troubleshooting the Antibiotic Prescription - L Sulz (April 26, 2015)