Tocolytic
{{Short description|Drugs used to suppress premature births}}
{{Use dmy dates|date=March 2020}}
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| specialty =OB/GYN
| synonyms = Labor suppressants
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Tocolytics (also called anti-contraction medications or labor suppressants) are medications used to suppress premature labor (from Greek τόκος tókos, "childbirth", and λύσις lúsis, "loosening"). Preterm birth accounts for 70% of neonatal deaths.{{Cite journal|date=2016|title=Practice Bulletin No. 171: Management of Preterm Labor|url=https://dx.doi.org/10.1097/AOG.0000000000001711|journal=Obstetrics & Gynecology|language=en-US|volume=128|issue=4|pages=e155–e164|doi=10.1097/AOG.0000000000001711|pmid=27661654|issn=0029-7844|author1=American College of Obstetricians Gynecologists' Committee on Practice Bulletins—Obstetrics|s2cid=5537988|url-access=subscription}} Therefore, tocolytic therapy is provided when delivery would result in premature birth, postponing delivery long enough for the administration of glucocorticoids (which accelerate fetal lung maturity) to be effective, as they may require one to two days to take effect.
Commonly used tocolytic medications include β2 agonists, calcium channel blockers, NSAIDs, and magnesium sulfate. These can assist in delaying preterm delivery by suppressing uterine muscle contractions and their use is intended to reduce fetal morbidity and mortality associated with preterm birth.{{Citation|last1=Mayer|first1=Christopher|title=Tocolysis|date=2021|url=http://www.ncbi.nlm.nih.gov/books/NBK562212/|work=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=32965883|access-date=2021-07-29|last2=Apodaca-Ramos|first2=Irasema}} The suppression of contractions is often only partial and tocolytics can only be relied on to delay birth for a matter of days. Depending on the tocolytic used, the pregnant woman or fetus may require monitoring (e.g., blood pressure monitoring when nifedipine is used as it reduces blood pressure; cardiotocography to assess fetal well-being). In any case, the risk of preterm labor alone justifies hospitalization.
Indications
Tocolytics are used in preterm labor, which refers to when a baby is born too early before 37 weeks of pregnancy. As preterm birth represents one of the leading causes of neonatal morbidity and mortality, the goal is to prevent neonatal morbidity and mortality through delaying delivery and increasing gestational age by gaining more time for other management strategies like corticosteroids therapy that may help with fetus lung maturity.{{Cite book|last1=Ouzounian|first1=Joseph G|title=Management of Common Problems in Obstetrics and Gynecology.|last2=Goodwin|first2=T. Murphy|last3=Paulson|first3=Richard J|last4=Montoro|first4=Martin N|last5=Muderspach|first5=Laila I|last6=Roy|first6=Subir|publisher=Blackwell Publishing Ltd|year=2010|isbn=9781444323030|pages=9–11}}{{Cite journal|last1=Harrison|first1=Margo S.|last2=Goldenberg|first2=Robert L.|date=2016|title=Global burden of prematurity|url=https://pubmed.ncbi.nlm.nih.gov/26740166/|journal=Seminars in Fetal & Neonatal Medicine|volume=21|issue=2|pages=74–79|doi=10.1016/j.siny.2015.12.007|issn=1878-0946|pmid=26740166}} Tocolytics are considered for women with confirmed preterm labor between 24 and 34 weeks of gestation age and used in conjunction with other therapies that may include corticosteroids administration, fetus neuroprotection, and safe transfer to facilities.{{Cite journal|last1=Hanley|first1=Margaret|last2=Sayres|first2=Lauren|last3=Reiff|first3=Emily S.|last4=Wood|first4=Amber|last5=Grotegut|first5=Chad A.|last6=Kuller|first6=Jeffrey A.|date=2019|title=Tocolysis: A Review of the Literature|url=https://pubmed.ncbi.nlm.nih.gov/30648727/|journal=Obstetrical & Gynecological Survey|volume=74|issue=1|pages=50–55|doi=10.1097/OGX.0000000000000635|issn=1533-9866|pmid=30648727|s2cid=58563849}}
Types of agents
There is no clear first-line tocolytic agent.{{Cite journal|vauthors=Tan TC, Devendra K, Tan LK, Tan HK |title=Tocolytic treatment for the management of preterm labour: a systematic review |journal=Singapore Med J |volume=47 |issue=5 |pages=361–6 |date=May 2006 |pmid=16645683 }}{{Cite journal |vauthors=de Heus R, Mol BW, Erwich JJ, etal |title=Adverse drug reactions to tocolytic treatment for preterm labour: prospective cohort study |journal=BMJ |volume=338 |pages=b744 |year=2009 |pmid=19264820 |pmc=2654772 |doi= 10.1136/bmj.b744}} Current evidence suggests that first line treatment with β2 agonists, calcium channel blockers, or NSAIDs to prolong pregnancy for up to 48 hours is the best course of action to allow time for glucocorticoid administration.
Various types of agents are used, with varying success rates and side effects. Some medications are not specifically approved by the U.S. Food and Drug Administration (FDA) for use in stopping uterine contractions in preterm labor, instead being used off-label.{{cn|date=February 2022}}
According to a 2022 Cochrane review, the most effective tocolytics for delaying preterm birth by 48 hours, and 7 days were the nitric oxide donors, calcium channel blockers, oxytocin receptor antagonists and combinations of tocolytics.{{cite journal |last1=Wilson |first1=Amie |last2=Hodgetts-Morton |first2=Victoria A |last3=Marson |first3=Ella J |last4=Markland |first4=Alexandra D |last5=Larkai |first5=Eva |last6=Papadopoulou |first6=Argyro |last7=Coomarasamy |first7=Arri |last8=Tobias |first8=Aurelio |last9=Chou |first9=Doris |last10=Oladapo |first10=Olufemi T |last11=Price |first11=Malcolm J |last12=Morris |first12=Katie |last13=Gallos |first13=Ioannis D |title=Tocolytics for delaying preterm birth: a network meta-analysis (0924) |journal=Cochrane Database of Systematic Reviews |date=10 August 2022 |volume=2022 |issue=8 |pages=CD014978 |doi=10.1002/14651858.CD014978.pub2|pmid=35947046 |pmc=9364967 }}
Calcium-channel blockers (such as nifedipine) and oxytocin antagonists (such as atosiban) may delay delivery by 2 to 7 days, depending on how quickly the medication is administered.
{{Cite journal
|vauthors=Iams JD, Romero R, Culhane JF, Goldenberg RL |year=2008
|title=Primary, secondary, and tertiary interventions to reduce the morbidity and mortality of preterm birth
|journal=The Lancet
|volume=371 |issue=9607 |pages=164–175
|pmid=18191687
|doi=10.1016/S0140-6736(08)60108-7
|s2cid=8204299
}} NSAIDs (such as indomethacin) and calcium channel blockers (such as nifedipine) are the most likely to delay delivery for 48 hours, with the least amount of maternal and neonatal side effects.{{Cite journal|last1=Haas|first1=David M|last2=Caldwell|first2=Deborah M|last3=Kirkpatrick|first3=Page|last4=McIntosh|first4=Jennifer J|last5=Welton|first5=Nicky J|date=2012|title=Tocolytic therapy for preterm delivery: systematic review and network meta-analysis|journal=The BMJ|volume=345|pages=e6226|doi=10.1136/bmj.e6226|issn=0959-8138|pmc=4688428|pmid=23048010}} Otherwise, tocolysis is rarely successful beyond 24 to 48 hours because current medications do not alter the fundamentals of labor activation.
{{Cite journal
|vauthors=Simhan HN, Caritis SN |year=2007
|title=Prevention of Preterm Delivery
|journal=New England Journal of Medicine
|volume=357 |pages=477–487
|pmid=17671256
|doi=10.1056/NEJMra050435
|issue=5
}} However, postponing premature delivery by 48 hours appears sufficient to allow pregnant women to be transferred to a center specialized for management of preterm deliveries, and thus administer corticosteroids for the possibility to reduce neonatal organ immaturity.
The efficacy of β-adrenergic agonists, atosiban, and indomethacin is a decreased odds ratio (OR) of delivery within 24 hours of 0.54 (95% confidence interval (CI): 0.32-0.91) and 0.47 within 48 hours (OR 0.47, 95% CI: 0.30-0.75).
Antibiotics were thought to delay delivery, but no studies have shown any evidence that using antibiotics during preterm labor effectively delays delivery or reduces neonatal morbidity. Antibiotics are used in people with premature rupture of membranes, but this is not characterized as tocolysis.{{Cite journal|last1=Kenyon|first1=Sara|last2=Boulvain|first2=Michel|last3=Neilson|first3=James P.|date=2013-12-02|title=Antibiotics for preterm rupture of membranes|url=https://pubmed.ncbi.nlm.nih.gov/24297389/|journal=The Cochrane Database of Systematic Reviews|issue=12|pages=CD001058|doi=10.1002/14651858.CD001058.pub3|issn=1469-493X|pmid=24297389|pmc=11297390}}
Contraindications to tocolytics
In addition to drug-specific contraindications,{{Cite journal|last1=Rundell|first1=Kristen|last2=Panchal|first2=Bethany|date=2017|title=Preterm Labor: Prevention and Management|url=https://www.aafp.org/afp/2017/0315/p366.html|journal=American Family Physician|volume=95|issue=6|pages=366–372|pmid=28318214|issn=0002-838X}} several general factors may contraindicate delaying childbirth with the use of tocolytic medications.
- Fetus is older than 34 weeks gestation{{cite book | last1=Wong | first1=D. L. | last2=Perry | first2=S. E. | last3=Hockenberry | first3=M. J. | last4=Lowdermilk | first4=D. L. | title=Maternal Child Nursing Care | publisher=Mosby | year=2002 | isbn=978-0-323-01399-4 | url=https://books.google.com/books?id=n_qBQgAACAAJ}}
- Fetus weighs less than 2.5 kg, or has intrauterine growth restriction (IUGR) or placental insufficiency
- Lethal congenital or chromosomal abnormalities
- Cervical dilation is greater than 4 centimeters
- Chorioamnionitis or intrauterine infection is present
- Pregnant woman has severe pregnancy-induced hypertension, severe eclampsia/preeclampsia, active vaginal bleeding, placental abruption, a cardiac disease, or another condition which indicates that the pregnancy should not continue.
- Maternal hemodynamic instability with bleeding
- Intrauterine fetal demise, lethal fetal anomaly, or non-reassuring fetal status
Future direction of tocolytics
Most tocolytics are currently being used off-label. The future direction of the development of tocolytics agents should be directed toward better efficacy in intentionally prolonging pregnancy. This will potentially result in less maternal, fetal, and neonatal adverse effects when delaying preterm childbirth. A few tocolytic alternatives worth pursuing include Barusiban, a last generation of oxytocin receptor antagonists, as well as COX-2 inhibitors.{{Cite journal|last1=Hubinont|first1=C.|last2=Debieve|first2=F.|date=2011|title=Prevention of Preterm Labour: 2011 Update on Tocolysis|journal=Journal of Pregnancy|language=en|volume=2011|page=941057|doi=10.1155/2011/941057|pmid=22175022|pmc=3228310|issn=2090-2727|doi-access=free}} More studies on the use of multiple tocolytics must be directed to research overall health outcomes rather than solely pregnancy prolongation.{{Cite journal|last1=Cole|first1=Stephen|last2=Smith|first2=Roger|last3=Giles|first3=Warwick|date=2004|title=Tocolysis: current controversies, future directions|url=https://pubmed.ncbi.nlm.nih.gov/15134284|journal=Current Opinion in Investigational Drugs |volume=5|issue=4|pages=424–429|issn=1472-4472|pmid=15134284}}
See also
References
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{{Other gynecologicals}}
Category:Chemical substances for emergency medicine