Drugs and Radiation during Pregnancy

Drugs and Radiation in Pregnancy

Medications

Analgesics

APAP(A) or morphine(C)

Can use NSAIDs except ASA (B) but no reason to use them.

ABX

PCNs (B), no reported problems

Erythromycin (B), except EES which can cause liver toxicity

Metronidazole (B), considered safe any trimester by OB, can use single dose regimen

Aminoglycosides (B), especially gentamycin and vancomycin, are safe. Must use higher doses b/c of serum expansion during pregnancy

Sulfa (C) meds are safe in all of preg but third trimester

Antiemetics

Prochlorperazine/Compazine (C) Promethazine/Phenergan (C) Metoclopramide/Reglan (C) Trimethobenzamide/Tigan (C) Ondansetron (Zofran) (B)

All are safe at any stage

Anticoagulants

Heparin-UFH or LMH are safe.

Anticonvulsants

Benzodiazepines (D) are indicated, just as in the nonpregnant state, to stop active seizures. Otherwise, consult OB.

Asthma Medications

Albuterol (C) and Ipatropium (B) are safe.

Steroids (B) are especially safe. Predinisone is probably best choice.

Antidysrhythmics

Lidocaine (B), Amiodarone (D), & Direct current cardioversion-considered safeAdenosine (C) also safe

Magnesium sulfate (A) is primarily used in pregnancy for tocolysis, treatment of hypomagnesemia and seizures and in the treatment of ventricular arrhythmias.

Any drug is safe in ACLS situation, save mother first.

Anti-Hypertensives

ACE inhibitors (D)-unsafe and should not be used.

B blockers (C) cross the placenta, but there is extensive experience with these medications and they all appear safe. Especially Labetalol (C)

Hydralazine (C) is the most commonly used of the antihypertensives. It is considered safe and has traditionally been considered the drug of choice for moderate to severe hypertension in patients with preeclampsia.

Methyldopa (B) is considered safe and is currently the drug of choice in pregnant patients for long-term therapy of hypertension. It can be combined with other agents, if indicated.

Substance Abuse in pregnancy

Opiates-neonatal withdrawl

Cocaine-placental abruption

Diagnostic Imaging in Pregnancy

As far as shielding is concerned, this is helpful in plan X-ray studies to reduce scattered radiation. Its effect during CT scanning is limited. This is because the CT bean is like a pencil beam, with little scattering. The main scattering from an abdominal CT, for example, is from radiation scattered off the spine which is obviously unaffected by shielding. It is generally accepted that exposures of less that 5 rads do not expose the fetus to risk. Other authors are willing to state that no significant risk exists up to doses of 10 rads. These doses should be considered cumulative for the duration of the specific pregnancy, but as the table below demonstrates, even multiple diagnostic X-ray procedures will rarely result in ionizing radiation exposure to this degree. As the table below demonstrates, even multiple diagnostic X-ray procedures will rarely result in ionizing radiation exposure to this degree.

C spine <0.001 rad Chest X-ray (2 view) 0.02-0.07 rad Abdominal film (single view) 0.1-0.5 rad Pelvic X-ray 0.15-0.5 rad CT head or chest <1 rad CT abdomen and lumbar spine 3.5 rad

The other imaging modality we frequently order is a V·Q (ventilation perfusion) nuclear scan for pulmonary embolus. In this study, the ventilation portion is performed first with either technetium 99 diethylenetriaminepentaacetic acid (DTPA) or xenon gas. Most centers still use DTPA, since this gas persists long enough to enable the technician to obtain the same 6 views that will be obtained in the next step, the perfusion scan. When xenon gas is used, only one image can be obtained. Following ventilation imaging, macroaggregated albumin (MAA) labeled with technetium 99 is injected intravenously to assess perfusion. The patient is then scanned and six views of the lungs in various planes are obtained and compared to the ventilation imaging for correlation. The V·Q scan is adapted to special situations such as pregnancy. In pregnancy, one half of the normal dose of the MAA is used. This is done because of the anatomy of the lung in pregnant patients, wherein less alveoli are ventilated and perfused due to the elevated diaphragms. It is not done to reduce the dose of radiation to the fetus, as this is considered to be minimal even at normal doses of MAA and DTPA. Scanning time with the gamma camera is minimally lengthened with this technique. It is sometimes suggested that only the perfusion portion of the V·Q scan be performed since if this is abnormal, the diagnosis will be made with less radiation exposure. This is acceptable but somewhat problematic. This is because the MAA used in the perfusion portion of the scan persists for some time in the vascular bed and as such the ventilation scan must be done first. If this technique is pursued and the perfusion scan is equivocal, there will be no ventilation images with which to compare and the test will be compromised. Given the very low radiation doses used normally and the potential additional confusion over the test result, I would not recommend this technique. There is no known risk from the actual technetium, DTPA or xenon and the radiation dose from the full ventilation and perfusion phases of the scan are considered safe. This is because the uterus, embryo or fetal exposure from the average procedure is between 0.05 rads and 0.5 rads. Failure to diagnose pulmonary embolus in this case is the much greater risk, especially considering the hypercoaguable status of the pregnant female and the ability to intervene in this disease and significantly affect morbidity and mortality. There are no known adverse fetal affects from ultrasound, which is widely used and considered safe. There are no documented adverse fetal affects from MRI, which uses magnets to alter the energy state of the bodys hydrogen protons. Despite this, the National Radiological Protection Board advises against its use in the 1st trimester. This is a totally unsupported recommendation. There is little data available data on gadolinium, the most common contrast material used with MRI scanning. This is generally considered safe in pregnancy.

All above from Emedhome.com Article

Winer-Muram HT, Boone JM, Brown HL, Jennings SG, Mabie WC, Lombardo GT. Pulmonary embolism in pregnant patients: fetal radiation dose with helical CT. Radiology 2002;224:487-92. PURPOSE: To calculate mean fetal radiation dose from helical chest computed tomography (CT) by using maternal-fetal geometries obtained from healthy pregnant women and to compare the calculated CT doses with the fetal doses reported with scintigraphy. MATERIALS AND METHODS: Maternal-fetal geometries were determined in 23 pregnant women with varying body mass index and fetal gestational age. Monte Carlo techniques were used to estimate the dose that would be received by each fetus from CT scanning performed with the following parameters: 120 kVp; 100 mA; scanning time, 1 second per section; collimation, 2.5 mm; pitch of 1. Craniocaudal extent of the scan was 11 cm, with the most caudal section edge being 5 mm inferior to the xiphoid process. RESULTS: For helical CT, estimated mean fetal doses in micrograys at varying gestational ages were as follows: 3.3-20.2 microGy, first trimester; 7.9-76.7 microGy, second trimester; and 51.3-130.8 microGy, third trimester. These values were all less than mean fetal doses reported with scintigraphy, with 37-74 MBq of macroaggregates of human serum albumin labeled with technetium 99m. If 200 mAs (pitch of 1.8) was used, the mean fetal doses were still less than those with scintigraphy. CONCLUSION: The average fetal radiation dose with helical CT is less than that with ventilation-perfusion lung scanning during all trimesters. Copyright RSNA, 2002

PE Imaging in Pregnancy

Imaging in Pregnancy

Up to 5 rads is tolerated

Start with Ultrasound of Legs

CTA-2 rads

Pulmonary Angiogram .045-.050 Rads

Perfusion Scanning .006-.018 Rads

Ventilation Scanning .001-.019 Rads

C-XR .001 Rads

BMJ 2005;331:350 (6 August), doi:10.1136/bmj.331.7512.350 Letter Radiation from CT and perfusion scanning in pregnancy EDITORIn her news article Eaton notes that most of the rise in medical radiation exposure is due to computed tomography.1 However, the whole body effective dose given for computed tomography may not reflect the increased risk to individual exposed body areas. Last year we assessed the risks for pregnant women undergoing investigation for possible pulmonary embolism.2 The British Thoracic Society guidelines 2003 recommend computed tomography for pulmonary angiography as the modality of choice for non-massive pulmonary emboli.3 It is also recommended for pregnant women because of the low fetal dose compared with low dose (50 milliBequerel) technetium-99m perfusion lung scans. According to our local data, the maternal whole body effective dose for computed tomography for pulmonary angiography was 2 milliSievert (mSv) compared with 0.6 mSv for a low dose perfusion scan. The absorbed doses to the fetus were 0.01 milliGray (mGy; risk of fatal cancer to the age of 15 years is < 1/1 000 000) for computed tomography for pulmonary angiography and 0.12 mGy (risk of 1/280 000) for the perfusion scan. This shows a distinct advantage to the fetus of performing computed tomography for pulmonary angiography. However, the absorbed doses to the breast were 10 mGy for computed tomography for pulmonary angiography and 0.28 mGy for a perfusion scan, about 40 times the dose to the breast at a time when proliferating, pregnant breast tissue would be expected to be at greater risk. When available and appropriate, lung perfusion scans should be considered the investigation of first choice for any young woman. Pregnant women with a family history of breast cancer or who have had previous computed tomography for pulmonary angiography may wish to elect for lung perfusion scans, despite the slightly higher risk to the fetus. Computed tomography is a valuable, but high dose, investigation. Although the overall risk is very small and usually completely outweighed by the benefits of obtaining a prompt diagnosis, it is still important to choose the technique that entails the least risk. J Valmai Cook, consultant radiologist Epsom and St Helier University NHS Trust, Carshalton, Surrey SM5 1AA Valmai.cook@epsom-sthelier.nhs.uk John Kyriou, radiation protection adviser Radiological Protection Centre, St George’s Hospital, London SW17 0QT John.kyriou@stgeorges.nhs.uk Competing interests: None declared. References Eaton L. UK agency reports slight increase in radiation exposure. BMJ 2005;330: 1229. (28 May.)[Free Full Text] Potter K, Kyriou J, Cook JV. Comparison of the radiation dose to the breast during CT pulmonary angiography and lung perfusion scanning. Implications for the diagnosis of pulmonary embolism during pregnancy. London: Royal College of Radiologists, 2005. (Ansell poster prize.) British Society Standards of Care Committee. British Thoracic Society guidelines for the management of suspected acute pulmonary embolism. Guideline Development Group. Thorax 2003;58: 470-83.[Free Full Text]

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