The first generation antihistamines include drugs such as diphenhydramine, cyproheptadine, promethazine, chlorpheniramine, and hydroxyzine. They have a very potent effect with high lipophilicity but are short acting. They are metabolized in the liver by the microsomal cytochrome P system. The common side effects of this category of antihistamines include sedation and anticholinergic effects—dryness of the mouth, blurring of vision, constipation and urinary retention.
FDA has categorized the first generation antihistamines according to the pregnancy complications [ Table 1 ]. Michigan Medicaid Birth Defects study has linked hydroxyzine to cleft palate in new borns. Pregnancy category B means the drug has failed to demonstrate a risk to the fetus in animal reproduction studies and there is a lack of well-controlled studies in pregnant women or animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.
Pregnancy category C means that animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant the use of the drug in pregnant women despite potential risks. The second generation antihistamines include drugs such as loratadine, fexofenadine, cetirizine, and azelastine.
They have a high therapeutic index, with highly selective actions and are nonsedating. They are long acting, but are poorly lipophilic and hence have no entry to the central nervous system.
Side effects of the second generation antihistamines include photosensitivity, tachycardia, and prolongation of the Q—T interval. FDA has categorized the second generation antihistamines as shown in [ Table 2 ].
Fexofendine and desloratidine have been classified as pregnancy category C. Reduction in pup weight and survival were observed with fexofenadine. There are no human data on fexofenadine and loratadine for them to be categorized as safe during pregnancy. Loratadine had previously been proposed as a possible factor for the increased incidence of hypospadiasis in infants born to mothers who had taken loratadine during pregnancy.
FDA pregnancy category classification for second-generation antihistamines[ 10 ]. Although pruritus is not a life-threatening medical condition, it can be extremely troublesome for pregnant women. Because of potential effects on the fetus, the treatment of pruritus in pregnancy requires prudent consideration. At one point, the physician will have to use the antihistamines and weigh the benefits against the teratogenic effects of the antihistamines.
Physicians must decide whether to select an older, better-studied antihistamine, thought to be relatively safe during pregnancy, or a newer agent that has less adverse effect on quality of life but has a potential teratogenic effect.
Various recommendations and studies favor the use of first generation antihistamines for use during pregnancy. More data are available about the various effects of the first generation antihistamines in pregnancy. In , the National Asthma Education and Prevention Program NAEPP Working Group on Asthma and Pregnancy recommended the first-generation agents chlorpheniramine and tripelennamine as the antihistamines of choice during pregnancy, based on duration of availability as well as reassuring animal and human data.
In general, second-generation antihistamines are more potent, have a longer duration of action, and produce minimal sedation. Other studies suggest that there is insufficient evidence to support the first-line use of cetirizine and loratadine during pregnancy and recommend first considering chlorpheniramine, tripelennamine, or hydroxyzine if an antihistamine is needed during pregnancy.
In every pregnant case with pruritus the basic cause of pruritus should first be sought out before starting the antihistamines. Appropriate investigations should also be done. The patient should be explained the fact that though no definite teratogenic effects have been reported to be associated with the intake of antihistamines in pregnancy, they are not licensed by the FDA as category A or the safe group. Also it is important to mention that in India no definitive guidelines have been given or followed by the government to prevent the use of H1-antihistamines as over the counter medicines.
Even for prescription purposes, no definitive guidelines have been given by the government and practitioners generally follow the FDA criteria. If possible the pruritus and other allergic manifestations in the first trimester of pregnancy should be managed using topical medications like bland emollients and systemic antihistamines should be avoided as none of the antihistamines are categorized as safe by the FDA and in India no specific guidelines exist regarding their use in pregnancy.
If antihistamines have to be prescribed then first generation agents should be preferred and among them chlorpheniramine, dexchlorpheniramine and hydroxyzine should be the first choice of agents. The patient should also be advised to drink plenty of water when taking antihistamines during pregnancy to overcome the anticholinergic side effects.
They should also be advised to take immediate gynecological consultation if they find any change in the frequency of baby's movement or increased contractions after taking the drugs. If a second generation agent has to be used then loratadine or cetirizine should be preferred as they have been widely studied for possible teratogenic effects and have been found to be nonteratogenic till date.
Both these agents are pregnancy category B agents. Second generation agents are preferably used after the first trimester if it has to be and preferably avoided in the early pregnancy when organogenesis takes place. To conclude first generation antihistamines such as chlorpheniramine, hydroxyzine, and dexchlorpheniramine are the safest among antihistamines to be used in pregnancy.
Histamine is produced by the body in response to foreign substances which the body is allergic to. Ask your doctor or pharmacist if you have any questions about why Polaramine has been prescribed for you. Some of the symptoms of an allergic reaction may include skin rash, difficulty in breathing or faintness. Taking Polaramine together with a MAOI may exaggerate the effects of Polaramine and cause a severe drop in your blood pressure.
If you are not sure whether you should start using Polaramine, talk to your doctor or pharmacist. Tell your doctor or pharmacist if you have allergies to any other medicines, any other substances such as foods, dyes or preservatives. Tell your doctor or pharmacist if you are pregnant or intend to become pregnant. If you are in the third trimester of pregnancy, you must tell your doctor you are taking Polaramine because newborn babies may have severe reactions to antihistamine.
Tell your doctor or pharmacist if you are breast-feeding or plan to breast-feed. Polaramine may be transferred in breast milk to your baby. Tell your doctor or pharmacist if you have or have had any medical conditions, especially the following:. If you have not told your doctor or pharmacist about any of the above, tell them before you start taking Polaramine.
Tell your doctor or pharmacist if you are taking any other medicines, including medicines that you buy without a prescription from a pharmacy, supermarket or health food shop. Some medicines should not be taken with Polaramine. These include: monoamine oxidase inhibitor MAOI. These medicines may be affected by Polaramine and may cause a decrease in blood pressure. These medicines may be affected by Polaramine, or may affect how well it works. You may need different amounts of your medicine, or you may need to take different medicines.
Your doctor or pharmacist will advise you. Your doctor or pharmacist has more information on medicines to be careful with or avoid while taking Polaramine. Take Polaramine exactly as your doctor or pharmacist has told you to. If you take the wrong dose, Polaramine may not work as well and you may not get relief from your symptoms. If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to.
If there is still a long time to go before your next dose, take it as soon as you remember, and then go back to taking your medicine as you would normally. Immediately telephone your doctor, pharmacist or Poisons Information Centre 13 11 26 for advice, or go to casualty at your nearest hospital, if you think that you or anyone else may have taken too much Polaramine.
Do this even if there are no signs of discomfort or poisoning. You may need urgent medical attention. If you take too much Polaramine, you may feel dizzy or light-headed and may have difficulty breathing. Tell all doctors, dentists and pharmacists who are treating you that you are taking Polaramine.
Do not take Polaramine to treat any other complaints unless your doctor or pharmacist says to. Do not drink alcohol while taking Polaramine. The effects of alcohol can be increased by some antihistamine medicines, including Polaramine.
If you drink alcohol, the drowsiness, dizziness or light-heade dness may become worse. If you feel tired, drowsy, dizzy or light-headed, do not drive a vehicle or operate machinery. As with some other antihistamine medicines, Polaramine may cause tiredness, drowsiness, dizziness or light-headedness in some people. Polaramine may cause your skin to be more sensitive than it is normally.
If your mouth continues to feel dry for more than 2 weeks check with your doctor or dentist. Read more on Sleep Health Foundation website. Measles is a highly infectious disease caused by a virus. It is most common in children and is spread by coughing, sneezing or sometimes kissing.
Find out what products are available for measles. Read more on myDr website. A major cause of eye problems is allergic, bacterial or viral conjunctivitis inflammation of the 'wet' surfaces of the eye. Find out what products are available for conjunctivitis. Chickenpox is a highly contagious disease caused by a viral infection. Most children with chickenpox develop an itchy rash that lasts for about 10 days. Antihistamines work fast and are good at treating mild symptoms of hay fever, such as sneezing and runny nose, whereas corticosteroid nasal sprays may take several days to work.
Most sinus problems are due to allergy, infection, or a foreign substance inhaled up the nose. Find out what products are available for sinus and nasal problems. Healthdirect Australia is not responsible for the content and advertising on the external website you are now entering.
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