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The use of drugs and vitamins during pregnancy |
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The use of drugs and vitamins during pregnancy
14 January 2000 -- Tan Lai-Lee
Pharmacist
The use of medications in pregnancy has always been a subject of concern among many would-be mothers. From conception to delivery, most pregnant women suffer from some form of minor ailment such as nausea and vomiting.
Although, it seems easy to recommend that no medication be taken at all during pregnancy unless the potential benefits outweighs any risk, this is very often not possible. Treatment is usually necessary to provide relief for the symptoms which these ailments inflict. At other times, treatment is indicated to treat potentially dangerous conditions during pregnancy.
Your doctor is probably the best person to diagnose and to treat you during this period. This article, however, serves to provide information to allow you to be actively involved in self-care during pregnancy and to provide you with a level of confidence in the use of medications during pregnancy.
Guidelines on the safe use of medications during pregnancy
The following are some guidelines for using medications during pregnancy. They are by no means to replace the advice and care provided by your doctor. Under no circumstance should you stop the medications prescribed by your doctor without proper consultation!
1. When using over-the-counter medications, always consult your doctor or your pharmacist.
2. Medications should only be used if the benefits of the treatment outweigh the potential risks.
3. Consider non-drug therapies if the condition permits, such as relief of minor muscular aches with warm baths or massage.
4. Where possible, use only one medication at each time.
5. The lowest possible dose for any medication should be used.
6. Use a topical preparation (e.g. creams) where available and where the condition permits.
7. Ideally and where possible, medications should be avoided during the first trimester.
8. Choose medications that have been widely used in pregnancy for years over the latest drugs.
Risk classification of drugs used during pregnancy
The U.S. Food and Drug Administration has classified drugs into five pregnancy categories. Most drugs are classified based on available clinical safety data and clinical experience with the drug potential benefits to the patients. Although the classification serves as a useful guide in the use of medications during pregnancy, it has its limitations. For instance, if the definitions of the various categories were to be strictly applied, many drugs would be relegated to Category C where "risk cannot be ruled out".
Category A: "Controlled studies show no risk. Adequate, well-controlled studies in pregnant women failed to demonstrate risk to the foetus."
Category B: "No evidence of risk in humans. Either animal findings show risk, but human findings do not; or, if no adequate human studies have been done, animal findings are negative."
Category C: "Risk cannot be ruled out. Human studies are lacking, and animal studies are either positive for foetal risk or lacking as well. However, potential benefits may justify the potential risk."
Category D: "Positive evidence of risk. Investigational or post-marketing data show risk to the foetus. Nevertheless, potential benefits may outweigh the potential risk."
Category X: "Contraindicated in pregnancy. Studies in human, animals, and investigational or post-marketing reports, have shown foetal risk, which clearly outweighs any possible benefit to the patient.
A subscript m after the category (e.g. Bm) is used to denote that the pregnancy category is listed in the manufacturer's product literature.
Use of medications during pregnancy
1. Treatment of nausea and vomiting
- First-line pharmacological treatment of nausea and vomiting in pregnancy is usually pyridoxine (pregnancy category A). Promethazine, an antihistamine has also been used, although the agent falls under pregnancy category C. Dimenhydrinate (pregnancy category Bm) and metoclopramide (pregnancy category Bm), both second-line pharmacological agents, have also been used in the treatment of nausea and vomiting.
2. Treatment of Cough
- Cough preparations commonly contain cough suppressants such as dextromethorphan (pregnancy category C) or codeine phosphate (pregnancy category C). Guafenesin (pregnancy category C), an expectorant is another commonly found agent in cough preparations.
Most of these agents may be used in the treatment of cough during pregnancy, although medications like codeine phosphate has been known to cause codeine withdrawal in the neonate. - Cough preparations that are alcohol-free are preferred over the alcoholic mixtures.
3. Treatment of Colds/Fever
- Antihistamines are commonly used in the management of colds (e.g. runny nose). First generation antihistamines such as chlorpheniramine (pregnancy category B) have been extensively used due to a long history of clinical experience. Others in this class include dexchlorpheniramine (pregnancy category Bm) and diphenhydramine (pregnancy category Bm). There is a relative lack of safety data with second-generation antihistamines such as loratidine (pregnancy category Bm); this is due mainly to their short product life in the market and thus a lack of clinical experience with them3.
- Pseudoephedrine (pregnancy category C), a common ingredient in cold preparations, is used commonly as a decongestant, despite controversial reports.
- Paracetamol/Acetaminophen (pregnancy category B) is used as an antipyretic and a painkiller. Due to its long history of use, paracetamol can be considered one of the safest medications that may be used during pregnancy.
4. Treatment of constipation - Non-drug therapies such as increasing the intake of fibre-containing foods and fluids are usually recommended for the pregnant women. Laxatives, when considered during pregnancy, usually belong to the class of bulk laxatives e.g. Ispaghula. Lactulose (pregnancy category Bm) may also be used.
5. Treatment of diarrhoea - If the use of anti-diarrhoeals is indicated during pregnancy, loperamide (pregnancy category Bm) is considered a safe option. Diphenoxylate (pregnancy category Cm) is not as highly recommended.
6. Treatment of infections - Antibiotics remain the main mode of pharmacological treatment for infections during pregnancy. Many antibiotics are used out of necessity during pregnancy. Virtually all are known to cross the placental barrier.
- Most antibiotics are classified as pregnancy category B (e.g. penicillins and cephalosporins), and are used rather extensively in pregnancy with a good safety record.
- Antibiotics that are not usually recommended due to their teratogenic potential (potential to cause foetal abnormality) include the tetracyclines (pregnancy category D) and the quinolones. Others that have been labelled pregnancy category C include vancomycin (pregnancy category Cm), trimethoprim (pregnancy category Cm), and the anti-tuberculosis agents isoniazid and rifampicin (pregnancy category C).
Use of vitamins during pregnancy
Multivitamin supplements are routinely prescribed for pregnant women, despite controversial reports with regard to its role in protecting the foetus against congenital anomalies. However, when used within the recommended limits, supplements are extremely safe for consumption during pregnancy and are essential to ensure that the pregnant mother receives adequate nutrition.
Generally, fat-soluble vitamins (vitamin A, D and E) are considered more toxic when consumed in doses above the recommended dietary allowance (RDA) as compared to their water-soluble counterparts (vitamin B and C).
Table 1. American (National Academy of Sciences) RDA for pregnant women as of 1989
| Vitamin A |
800 RE (retinol equivalent) |
| Vitamin D |
400 IU |
| Vitamin E |
10 IU |
| Vitamin B1 (Thiamine) |
1.5 mg |
| Vitamin B2 (Riboflavin) |
1.6 mg |
| Vitamin B3 (Niacinamide) |
17 mg |
| Vitamin B6 (Pyridoxine) |
2.2 mg |
| Vitamin B12 (Cyanocobalamin) |
2.2 m g (microgram) |
| Vitamin C |
70 mg |
| Folic acid |
0.4 mg |
References
- Sannerstedt R, Lundberg P, Danielsson BR, Kihlstrom I, Alvan G, Prame B, Ridley E. Drugs during pregnancy; An issue of risk classification and information to prescribers. Drug Safety 1996 (Feb);14(2):69-77
- Mangurten HH, Benawra R. Neonatal2 codeine withdrawal in infants of nonaddicted mothers. Pediatrics 1980;65:159-160
- Mazzotta P, Loebstein R, Koren G. Treating allergic rhinitis in pregnancy; safety considerations. Drug Safety 1999 (Apr);20(4):361-375
- Dashe JS, Gilstrap LC. Antibiotic use in pregnancy. Obstet Gynecol Clin North Am 1997 (Sep);24(3):617-629
Recommended Reading:
- Briggs GC: Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 5th Edition. 1998.
Date reviewed: 14 January 2000
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