Ritodrine and Isoxsuprine in Management of Preterm Labor

Yogol et al. Ritodrine and Isoxsuprine in Management of Preterm Labor
compared to Isoxsuprine. 11
There are no significant changes in pre- drug and post
drug monitoring parameters with either Isoxsuprine or
Ritodrine. However, uterine contraction was significantly
reduced after administration of drugs in both Ritodrine
and Isoxsuprine group which indicates uterine relaxant
effect of both drugs. Despite this, the rate of diminution
of number of uterine contractions was found to be higher
with Ritodrine than with Isoxsuprine which indicates that
Ritodrine has more rapid onset of action than Isoxsuprine.
This difference in onset of action could be due to the
difference in route of administration as Ritodrine was
initially administered intravenous while Isoxsuprine was
given orally. However, the results of this study suggest
that Ritodrine more effectively suppresses uterine motility
and also has lesser effects on maternal cardiovascular
system.
The direct cost of treatment with Ritodrine is higher than
that with Isoxsuprine; but it is still affordable to the
patient. The study carried out by Roy et al showed the
cost involved in Isoxsuprine treatment as compared to
Ritodrine treatment is in the ratio of 1:3. 7
In that study,
Isoxsuprine was used in injectable form as starting dose
followed by oral tablets after two to three days. In present
study only oral tablets of Isoxsuprine was used, which
could have resulted in the difference in cost of treatment
between the two studies.
The study showed Ritodrine has higher success rate than
Isoxsuprine in preventing preterm deliveries (93.5% vs
73.0%). It is well accepted that the consequences of
failure of tocolysis are neonatal morbidity and mortality,
which cost more than the direct cost of treatment of
preterm labor either with Ritodrine or with Isoxsuprine.
Again the incidences of overall adverse effects including
maternal cardiac side effects such as tachycardia and
hypotension were also significantly higher in Isoxsuprine
(26.7%) than in Ritodrine (6.5%). Several studies have
shown that Isoxsuprine has limited therapeutic value
with unpleasant side effects and efficacy. 7,8,10,12
Hence,
Ritodrine seems to be a much safer tocolytic agent than
Isoxsuprine. Although the direct cost of treatment with
Ritodrine is higher than that with Isoxsuprine, it is still
bearable to the patient. Hence, it could be the more
preferable betamimetic agent used as tocolytic agent
rather than Isoxsuprine.
Since the sample size of this study was small and the
study was conducted in only two hospitals of Nepal for
short duration, the study cannot be delineated to whole
population. Randomized control trials would have produced
more reliable results.
CONCLUSIONS
The study found that Ritodrine was significantly successful
in arresting preterm labor than Isoxsuprine. The study
also found that Ritodrine was comparatively safer than
Isoxsuprine in terms of occurrence of cardiac side effects
as well as extra cardiac maternal side effects. Although
cost of Ritodrine was higher than cost of Isoxsuprine,
it was justifiable in long term in view of increased
economic burden of tocolytic failure and increased adverse
effects.
ACKNOWLEDGEMENTS
Staff of Obstetrics and Gynecology Department of
Dhulikhel Hospital, Maternity Hospital Thapathali and
staffs of Pharmacy Department, Kathmandu University.
REFERENCES
1. Morrison JC. Preterm Labor: Prediction and Treatment.
Obstetrics and Gynecology Clinics of North America.
2005;32(3):369-81.
2. Gabby SG, Niebyl JP, Simpson JL. Preterm birth. Obstetrics,
Normal & Problem Pregnancies, 4th ed. Philadelphia: Churchill
Livingstone; 2002. p. 787-91.
3. Goldenberg RL & Rouse DJ. Prevention of preterm birth. N
Engl J Med 1998;339:313-20.
4. Papatsonis DNM, Van Geijn HP, Ader HJ, Lange FM, Bleker
OP, Dekker GA. Nifedipine and Ritodrine in the management
of preterm labor: a randomized multicenter trial. Obstet
Gynecol. 1997;90:230-4.
5. Gennaro AR, Chase GD, Marderosian AD, Hanson GR, Hussar
DA. Remington: The Science & Practice of Pharmacy. 19th ed.
USA: Mack Publishing Company; 1993. p. 992,998.
6. Sirohiwal D, Sachan A, Bano A, Gulati N. Evaluation of ritodrine
for tocolysis in preterm labor. J Obs Gyn. 2001;51:66-7.
7. Roy V, Prasad GS, Latha K. Tocolysis with Ritodrine: A
Comparative Study in Preterm Labor. Pakistan J Medical Sciences. 2006;22:1.
8. Ikeda S, Tamaoki H, Akahane M, Nebashi Y. Effect of ritodrine
hydrochloride, a beta 2- adrenoreceptor stimulant, on uterine
motilities in late pregnancy. Jpn J Pharmacol. 1984; 35(3):319-
26.
9. Newton ER. Preterm labor, preterm premature rupture of
membranes and chorioamnionitis. Clin Perinatol. 2005 Sep;
32(3):571-600.
10. Kazzi NJ Gross TL Kazzi GM Williams TG. Neonatal
complication following in utero exposure to intravenous
ritodrine. Acta Obstet Gynecol Scand. 1987;66(1):65-9.
11. Merkatz IR, Peter JB, Barden TP. Ritodrine hydrochloride: a
betamimetic agent for use in preterm labor. II. Evidence of
efficacy. Obstet Gynecol. 1980;56(1):7-12.
12. King JF, Grant A, Keirse MJ, Chalmers I. Betamimetics in
preterm labor. An overview of randomized controlled trials.
Br J Obstet Gynaecol. 1998;95:211-22.
268
JNMA I Vol 48 I No. 4 I Issue I176 I Oct-Dec, 2009