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Dr. B.R. Madan, former
Professor and Head of the Department of Pharmacology at
S.P. Medical College, Bikaner is currently the Editor of
'Dear Doctor', published by the Rajasthan Voluntary
Health Association, Jaipur.
There was a case from Germany in 1960 where a pregnant
women named ‘Sigi’ took the drug - thalidomide
- which was advertised as effective, safe, and
non-addictive hypnotic for treatment of her insomnia. She
delivered a monster which had no limps (phocomelia). Her
cherished dream of many years shattered to pieces!
This and many other cases of foetal malformations shook
the conscience of the doctors and awakened the medical
profession to the grim reality of drug-induced
teratogenicity, i.e. the production of structural,
biochemical and behavioural abnormalities in the
offspring when the drug is given to the mother during
pregnancy.
Since the thalidomide disaster, regulatory agencies in
different countries have become very strict in respect of
introducing new drugs until and unless teratogenic
potential has been properly evaluated. This is easier
said than done because there are wide species differences
and the relevance of animal testing for predicting
teratogenic effect in man is highly questionable.
Most physicians are now aware of the concept of
"critical period’ of developmental sensitivity
to drugs. It is between 21 and 35 days of intra-uterine
life. During this period, the main organ systems,
including CNS, heart and gut, differentiate and are most
vulnerable to the deleterious effects of drugs. However,
it is to be clearly understood that it is in the later
stages of pregnancy that histological, biochemical and
functional developments are their most active stages and
drugs may interfere with these. Thus all stages of
pregnancy must be regarded as potentially hazardous for
the foetus, and not just the first semester.
Fortunately, only a few drugs are definitely known to
cause congenital birth defects. But unfortunately,
relatively few drugs are known to be completely safe
during pregnancy.It is again unfortunate that for
most of the currently used drugs definite evidence is not
available regarding their safety or otherwise. That is
why it is ideal if no drug is given to a pregnant woman.
This is impracticable. So
if a drug has to be given, it should be in the smallest
effective dose for the shortest duration. Another dictum
in medical practice should be to avoid newly introduced
drugs since their full teratogenic potential has not been
assessed.
Antibiotics,
Chemotherapeutic Agents in Pregnancy
Anti-Malarials: Malaria in a pregnant woman
should be promptly and effectively treated.
It is recommended that the total dose of chloroquine be
calculated on weight basis, i.e. 25 mg/kg body weight,
and given over a period of 3 days. Quinine should be
reserved for resistant cases. In an attempt to counteract
any stimulant action of quinine on the uterus, some
obstetricians recommend the concurrent use of a tocolytic
agent. Pyrinethamine + sulphadoxine combination is to be
avoided if possible.
Anti-Amoebic
Agents: Metronidazole is safe in recommended
doses. No foetal malformations have been reported.
Diloxanide (for trophozoites in the gut) should be
avoided since its safety status is unclear.
Anti-Tubercular
Drugs: Isoniazid, ethambutol and pyrizinamide
can be safely used. No serious teratogenicity has been
reported with the use of rifampicin. However, there are a
few reports of bleeding in neonates due to
hypopro-thrombinemia. It may, therefore, be advisable to
give Vitamin K to the mother near term.
Anti-Helmintics:
Mebendazole, albendazole, pyrental pamoate etc. are
considered safe for use during pregnancy.
Penicillins:
Benzyle penicillin, ampicillin, amoxycillin,
cloxacillin are not teratogenic but sensitivity reactions
should be watched in the mother which may have
deleterious effect on the foetus.
Celphalosporins:
No foetal toxicity has been reported and they are
widely used during pregnancy.
Sulphanamides: They
can aggravate neonatal jaundice by displacing bilirubin
from serum albumin. They should not be used when labour
is imminent.
Cotrimoxazole:
It interferes with folic acid absorption and metabolism.
Although it has been used in pregnancy without any
apparent harm to the foetus, it is advisable to give
folic acid supplements (5 to 10 mg per day) to the
mother.
Aminoglycosides:
Gentamycin, streptomycin, neomycin and kanamycin
(amikacin) are ototoxic (eighth nerve damage) and
nephrotoxic for the foetus and are
Chloramphenicol:
Gray-baby syndrome can occur in neonates and it is a
dangerous complication. Avoid this antibiotic at term.
Cleft lip or palate has also been suspected due to
chloramphenicol.
Tetracyclines: Tooth
discolouration and dysplacia as well as inhibition of
bone growth may occur. Contraindicated in pregnancy.
Erythromycins,
Lincomycins, Vancomycin: They can be safely used.
Quinolones
(Ciprofloxacin, norfloxacin) : Since
there is insufficient information available regarding
their teratogenic potential, they are best avoided in
pregnancy.
Anti-Fungals: Nystatin,
micanazol and amphotericin are considered to be safe.
There is some evidence of teratogenicity in animals with
the use of ketoconazole and griseofulvin but the
significance of this in humans is uncertain.
Drugs Taken by the
Father
It must be stressed that severe maternal
disorders such as hyperemesis, toxaemias or epileptic
fits may be more dangerous than the potentially
teratogenic drugs used in their treatment. It is also
relevant to mention here that teratogenic effect on the
foetus may occur if some drugs are taken by the father as
well. Finasteride, a drug used to treat prostatic
hypertrophy, is excreted in the semen and may do damage
to the foetus. Men taking the drug are advised to use
condom lest their partner be comes pregnant with a
malformed foetus. Griseofulvin may damage sperm cells
and, therefore, men are advised not to father children
during, or for 6 months after, treatment.
For further information,
please write to:
Rajasthan Voluntary Health Association, 147 Milap Nagar,
Tonk Road, Jaipur - 302 018 Tel. 512021, 510178).
RVHA has recently set up an Obstetric Drug Information
Cell, with a computerized data-base on the safety status
of drugs in pregnancy and lactation. This Cell provides
relevant information to doctors as well as the patients.
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