pharmacology of gbs drugs -...
TRANSCRIPT
Pharmacology of GBS drugs
Presented by Vicki Penwell, CPM, LM, MSM, MA
Indications for Drug Prophyaxis
Positive GBS culture in current pregnancy
GBS bacteria cultured in urine during the current
pregnancy
Any woman who had a previous baby develop
group B strep disease
Signs and symptoms indicating risk in labor
When GBS status unknown
Signs and symptoms indicating risk if status
unknown
Labor starting at less than 37 weeks
Prolonged membrane rupture ( 18 or more
hours before delivery)
Fever during labor
Practices unsupported by research
Informal survey found that many different
treatment modalities are used by midwives for
preventing Early-Onset Group B Strep Disease in
the babies born to GBS positive women.
They include using a variety of treatments,
different antibiotics than what is recommended,
and administering antibiotics in timing other than
recommended
(Penwell et al)
Chlorhexidine Rinse
Birth canal washes with the disinfectant
chlorhexidine (Hibiclens) does not seem to
reduce the risk of a mother spreading group B
strep bacteria to her baby.
Although chlorhexadine reduces the risk of a
newborn being colonized with GBS, it has not
been shown to decrease the risk of actual GBS
infections in newborns.
(Stade et al. 2004)
Treatment before labor
Giving penicillin to women before labor does
not work. Although penicillin temporarily lowered
GBS levels, by the time women went into labor
the GBS levels were back up again.
(Gardner et al. 1979).
Oral or IM Antibiotics
Antibiotics taken by mouth or IM instead of
through IV are not effective at preventing group
B strep disease in babies.
(Easmon,Hastings 1983, CDC 2016)
Treatment after illness has begun
Due to treatment in labor, there has been a large drop in early GBS infection rates in the U.S.—from 1.7 cases per 1,000 births in 1990, to 0.25 cases per 1,000 births today
If a mother who carries GBS is not treated with antibiotics during labor, the baby’s risk of developing a serious, life- threatening GBS infection is 1 to 2%
(Boyer & Gotoff 1985; CDC 2012; Feigin, Cherry et al. 2009)
GBS and antibiotics
. To date, receiving antibiotics through IV during
labor, at least 4 hours before the birth, is the
only proven strategy to protect a baby from
early-onset group B strep disease.
Antibiotics for treating GBS during
labor, in order of recommendation
Penicillin
Ampicillin
If Penicillin allergy, may use:
Cefazolin
Alternative antibiotics include Clindaymycin and Vancomycin (not recommended except in rare cases of Penicillin anaphylaxis)
Know and Follow CDC Guidelines
Again, here we see a wide variance of actual
practice among midwives who treat GBS
positive women in labor with antibiotics.
Various reasons are given…including personal
preference, fear of drug reactions, how often
drug has to be administered, and availability of
drugs
Which Antibiotic to use?
The efficacy of Penicillin and Ampicillin as intravenously administered intrapartum agents for the prevention of early-onset neonatal GBS disease has been demonstrated in clinical trials and large observational studies. The efficacy of alternatives has not been evaluated. However, cefazolin has similar pharmacokinetics and dynamics to penicillin and ampicillin and achieves high intra-amniotic concentrations.
(CDC May 2016)
Microbiome Concerns
Penicillin is the anitbiotic of choice because it is
very specific to kill GBS and less likely to kill other
good bacteria.
Penicillin is recommended by CDC and ACOG
as first line drug to prevent early onset GBS
infections
Serious reactions to Penicillin are actually rare
(about 1 out of every 10,000 women)
Allergy or Anaphylaxis
Women who have a known allergy to Penicllin
can take Cefazolin instead. Cefazolin (like
Penicillin and Ampicillin) crosses the placenta
and reaches the fetus's bloodstream.
If woman has high risk for anaphylaxis with
penicillin, CDC recommends alternative
antibiotics include Clindaymycin and
Vancomycin.
Drawbacks of alternative drugs
Clindamycin and Vancomycin have never been tested in clinical trials for the prevention of early GBS infection.
Clindamycin and Vancomycin barely reach the fetal bloodstream, if at all.
GBS must be specifically tested to know that Clindamycin or Vancomycin will work on a woman’s particular strain of GBS.
Erythromycin should never be used at any time(CDC, 2010; Pacifici 2006)
Timing is everything
The CDC recommends that antibiotics be given every 4 hours, starting more than 4 hours before birth.
When Penicillin or Ampicillin was given more than 4 hours before birth, it was effective 89% of the time.
Giving antibiotics 2-4 hours before birth was effective 38% of the time.
(Fairlie et al., 2013)
Every 4 hours, for more than 4 hours
In another study, more infants whose mothers
received less than 4 hours of antibiotics had a
discharge diagnosis of sepsis when compared to
infants whose mothers received 4 hours or more
of antibiotics (1.4% versus 0.4%.)
(Turrentine et al., 2013)
Antibiotic Details
Indication
Dose
Route
Half Life
Storage
Why (Reason for use)
PenicillinRecommended by CDC, ACOG
Indication: Group B Strep Prophylaxis
Dose: 5 million units initial dose, then 2.5 million
units every 4 hours till birth.
Route: IV in .≥100 ml LR, NS, or D5LR
Half life: 42 minutes
Storage: Below 86 F
Why: Most specific, less “collateral damage”
AmpicillinAlternative if Penicillin not available
Indication: Group B Strep Prophylaxis
Dose: 2 grams initial dose, then 1 gram every 4
hours until birth
Route: IV in ≥ 100 ml NS or LR
Half life: 1 hour
Storage: 68-77 F
Why: Tolerated well if Penicillin not available
CefazolinOnly if Allergy to Penicillin exists
Indication: Group B Strep Prophylaxis
Dose: 2 grams initial dose, then 1 gram every 8
hours until birth
Route: IV in ≥ 100 ml LR, NS, or D5LR
Half life: 2 hours
Storage: 68-77 F
Why: drug of choice for Penicillin allergy with low
risk for anaphylaxis
ClindamycinOnly if anaphylaxis exits
Indication: Group B Strep Prophylaxis only if
absolutely necessary, and test GBS type first
Dose: 900 mg every 8 hours
Route IV in ≥ 100 ml NS only
Half Life: 2-3 hours
Storage: 68-77 F
Why: drug for use when severe penicillin
anaphylaxis exists and there is no other choice
VancomycinOnly if anaphylaxis exits
Indication: Group B Strep Prophylaxis only if
nothing else is possible, and test GBS type first
Dose: 1 g every 12 hours
Route: IV in LR or NS
Half Life: 4-6 hours
Storage: (59° to 86°F)
Why: Rarely ever used; does not seem to work
Anaphylaxis
Characterized by sudden onset of:
Rash/Hives; Flushing; Tissue swelling; Airway
obstruction; Hypotension; Diarrhea;
Brochospasm and Circulatory collaspe
Death from edema obstructing airway
Management of Anaphylactic
Shock
Stop the drug and call for help
Maintain airway, or start CPR
Adrenaline IM in lateral thigh
Repeat dose as necessary while urgently seeking
help from EMS
Epinephrine HCl
1:1000 ( EpiPen)
Indications: Treatment of severe allergic
reactions
Dose: 0.3 ml pre-metered dose
Route of Administration: Subcutaneously or
intramuscularly
Epinephrine HCl
1:1000 ( EpiPen), cont.
Duration of Treatment : Every 20 minutes or until EMS arrives.
Action time or half life : Works in Seconds. Lasts only 20 minutes or less.
Storage: Protect from light. 59-86 F (77 best). Do not refrigerate OR leave in car
Call 911 after administering
New Vaccine on the horizon
Pfizer is set to test a potential vaccine to prevent
GBS infections in Newborns
The Bill & Melinda Gates Foundation has
awarded a grant to support a study evaluating
a vaccine to protect newborns against group B
Streptococcus infection (GBS). The vaccine, still
in early stage development, t is designed to
protect newborns by immunizing their mothers.
Possible future vaccine
Evidence from studies has shown that a
potential conjugate vaccine, incorporating at
least five serotypes of GBS, could prevent
around 95 percent of group B streptococcal
disease in infants younger than three months.
Possible future vaccine, cont.
“We are looking to determine whether our
investigational vaccine could generate levels of
protective antibodies in the mother that, when
passed to her unborn baby, will protect the
baby against deadly GBS infection during a time
when the infant is most vulnerable to infection.”
Kathrin U. Jansen, PhD, head of Vaccine
Research & Development, Pfizer. Oct 2016
In closing– Important to keep
updating our knowledge on GBS
Thank you