Pharmacy

Zyrtec – General Information:

A potent second-generation histamine H1 antagonist that is effective in the treatment of allergic rhinitis, chronic urticaria, and pollen-induced asthma. Unlike many traditional antihistamines, it does not cause drowsiness or anticholinergic side effects.

Pharmacology:
Zyrtec, the active metabolite of the piperazine H1-receptor antagonist hydroxyzine, is used to treat chronic idiopathic urticaria, perennial allergic rhinitis, seasonal allergic rhinitis, allergic asthma, physical urticaria, and atopic dermatitis.
Zyrtec for patients

What is cetirizine?
- Cetirizine is an antihistamine. Cetirizine blocks the actions of the naturally occurring chemical histamine in the body. Cetirizine is less likely than some other antihistamines to cause side effects such as drowsiness and dizziness.
- Cetirizine is used to treat the symptoms of allergies such as sneezing; runny nose; itching, tearing, and redness of the eyes; and hives.
- Cetirizine may also be used for purposes other than those listed in this medication guide.

What should I discuss with my healthcare provider before taking cetirizine?
- Do not take cetirizine without first talking to your doctor if you have had an allergic reaction to it or to the medication hydroxyzine (Atarax, Vistaril).
- Before taking cetirizine, tell your doctor if you have kidney or liver disease. You may need a dosage adjustment or special monitoring during treatment.
- Cetirizine is in the FDA pregnancy category B. This means that it is not expected to be harmful to an unborn baby. Do not take cetirizine without first talking to your doctor if you are pregnant or could become pregnant during treatment.
- Cetirizine passes into breast milk and may affect a nursing baby. Do not take cetirizine without first talking to your doctor if you are breast-feeding a baby.
- If you are over 65 years of age, you may be more likely to experience side effects from cetirizine. Your doctor may prescribe a lower dose of this medication.

How should I take cetirizine?
- Take cetirizine exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.
- Take the tablets with a full glass of water.
- Chew the chewable tablets thoroughly before swallowing.
- To ensure you get the correct dose, measure the liquid form of cetirizine with a dose-measuring spoon, cup, or dropper, not with a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist where you can get one.
- Cetirizine can be taken with or without food.
- Store cetirizine at room temperature away from moisture and heat.
Zyrtec Interactions

Pharmacokinetic interaction studies with cetirizine in adults were conducted with pseudoephedrine, antipyrine, ketoconazole, erythromycin and azithromycin. No interactions were observed. In a multiple dose study of theophylline (400 mg once daily for 3 days) and cetirizine (20 mg once daily for 3 days), a 16% decrease in the clearance of cetirizine was observed. The disposition of theophylline was not altered by concomitant cetirizine administration.

Drug-Drug Interactions: No clinically significant drug interactions have been found with theophylline at a low dose, azithromycin, pseudoephedrine, ketoconazole, or erythromycin. There was a small decrease in the clearance of cetirizine caused by a 400-mg dose of theophylline; it is possible that larger theophylline doses could have a greater effect.
Zyrtec Contraindications

Cetirizine is contraindicated in those patients with a known hypersensitivity to it or any of its ingredients or hydroxyzine.

Periactin – General Information:

A serotonin antagonist and a histamine H1 blocker used as antipruritic, appetite stimulant, antiallergic, and for the post-gastrectomy dumping syndrome, etc.

Pharmacology:
Periactin is a piperidine antihistamine. Unlike other antihistamines, this drug also antagonizes serotonin receptors. This action makes Periactin useful in conditions such as vascular headache and anorexia. Periactin does not prevent the release of histamine but rather competes with free histamine for binding at HA-receptor sites. Periactin competitively antagonizes the effects of histamine on HA-receptors in the GI tract, uterus, large blood vessels, and bronchial smooth muscle. Most antihistamines possess significant anticholinergic properties, but Periactin exerts only weak anticholinergic actions. Blockade of central muscarinic receptors appears to account for Periactin’s antiemetic effects, although the exact mechanism is unknown. Periactin also competes with serotonin at receptor sites in smooth muscle in the intestines and other locations. Antagonism of serotonin on the appetite center of the hypothalamus may account for Periactin’s ability to stimulate appetite. Periactin also has been used to counter vascular headaches, which many believe are caused by changes in serotonin activity, however it is unclear how Periactin exerts a beneficial effect on this condition.
Periactin for patients

Antihistamines may diminish mental alertness; conversely, particularly, in the young child, they may occasionally produce excitation. Patients should be warned about engaging in activities requiring mental alertness and motor coordination, such as driving a car or operating machinery.
Periactin Interactions

MAO inhibitors prolong and intensify the anticholinergic effects of antihistamines. Antihistamines may have additive effects with alcohol and other CNS depressants, e.g., hypnotics, sedatives, tranquilizers, antianxiety agents.

Periactin Contraindications

Newborn or Premature Infants

This drug should not be used in newborn or Premature infants.

Nursing Mothers

Because of the higher risk of antihistamines for infants generally and for newborns and prematures in particular, antihistamine therapy is contraindicated in nursing mothers.

Other Conditions

Hypersensitivity to cyproheptadine and other drugs of similar chemical structure. Monoamine oxidase inhibitor therapy
Angle-closure glaucoma
Stenosing peptic ulcer
Symptomatic prostatic hypertrophy
Bladder neck obstruction
Pyloroduodenal obstruction
Elderly, debilitated patients