The action of the drug on the human body is called Pharmacodynamics in Medical terminology. To produce its effect and to change the pathological process that is happening the body and to reduce the symptom or cure the disease, the medicine has to function in a specific way. The changes it does to the body at cellular level gives the desired result of treating a disease. Drugs act by stimulating or inhibiting a receptor or an enzyme or a protein most of the times. Medications are produced in such a way that the ingredients target the specific site and bring about chemical changes in the body that can stop or reverse the chemical reaction which is causing the disease.
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Zalastin hydrochloride, a phthalazinone derivative, exhibits histamine H1-receptor antagonist activity in isolated tissues, animal models, and humans. Zalastin hydrochloride nasal solution (nasal spray) is administered as a racemic mixture with no difference in pharmacologic activity noted between the enantiomers in in vitro studies. The major metabolite, desmethylAzelastine, also possesses H1-receptor antagonist activity.
How should I take Zalastin?
Administration of drug is important to know because the drug absorption and action varies depending on the route and time of administration of the drug. A medicine is prescribed before meals or after meals or along with meals. The specific timing of the drug intake about food is to increase its absorption and thus its efficacy. Few work well when taken in empty stomach and few medications need to be taken 1 or 2 hrs after the meal. A drug can be in the form of a tablet, a capsule which is the oral route of administration and the same can be in IV form which is used in specific cases. Other forms of drug administration can be a suppository in anal route or an inhalation route.
Use Zalastin only as directed by your doctor. Do not use more of it and do not use it more often than your doctor ordered. To do so may increase the chance of side effects.
Zalastin usually comes with patient information insert. Read and follow the instructions carefully. Ask your doctor if you have any questions.
Zalastin is for use only in the nose. Do not get any of it in your eyes or on your mouth. If it does get on these areas, rinse it off with water and call your doctor right away.
Do not use Zalastin for any other nose problem without checking with your doctor first.
To use the spray:
When you use the Zalastin nasal spray for the first time, you must prime the spray. Press down fully the top of the pump 6 times or until a fine spray comes out. Prime again with 2 sprays if it has not been used for 3 or more days.
Gently blow your nose before using the spray. Tilt your head back slightly and insert the tip of the nose piece into your nostril.
Close the opposite nostril with a finger. Release 1 spray and at the same time, breathe in gently through the nostril.
Hold your breath for a few seconds then breathe out slowly through your mouth.
Spray the opposite nostril using the same steps.
Do not blow your nose or tip your head back after using the spray.
Wipe the tip of the outside of the nose piece with a clean, dry tissue or cloth and put the cap back on.
Throw Zalastin away after you use 200 sprays.
Dosing
The dose of Zalastin will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of Zalastin. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
For nasal dosage form (spray):
For treatment of perennial allergic rhinitis:
Adults and children 12 years of age—2 sprays in each nostril two times a day. Each spray contains 137 or 205.5 micrograms (mcg) of Zalastin.
Children 6 to 11 years of age—1 spray in each nostril two times a day. Each spray contains 137 or 205.5 mcg of Zalastin.
Children 6 months to 5 years of age—1 spray in each nostril two times a day. Each spray contains 137 mcg of Zalastin.
Children younger than 6 months of age—Use and dose must be determined by your doctor.
For treatment of seasonal allergic rhinitis:
Adults and children 12 years of age—1 or 2 sprays in each nostril two times a day, or 2 sprays in each nostril once a day. Each spray contains 137 or 205.5 micrograms (mcg) of Zalastin.
Children 6 to 11 years of age—1 spray in each nostril two times a day. Each spray contains 137 or 205.5 mcg of Zalastin.
Children 2 to 5 years of age—1 spray in each nostril two times a day. Each spray contains 137 mcg of Zalastin.
Children younger than 2 years of age—Use and dose must be determined by your doctor.
Missed Dose
If you miss a dose of Zalastin, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Storage
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Store the bottle upright with the pump tightly closed.
Zalastin pharmacology
Pharmacokinetics of a drug can be defined as what body does to the drug after it is taken. The therapeutic result of the medicine depends upon the Pharmacokinetics of the drug. It deals with the time taken for the drug to be absorbed, metabolized, the process and chemical reactions involved in metabolism and about the excretion of the drug. All these factors are essential to deciding on the efficacy of the drug. Based on these pharmacokinetic principles, the ingredients, the Pharmaceutical company decides dose and route of administration. The concentration of the drug at the site of action which is proportional to therapeutic result inside the body depends on various pharmacokinetic reactions that occur in the body.
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Mechanism of Action
Zalastin hydrochloride, a phthalazinone derivative, exhibits histamine H1-receptor antagonist activity in isolated tissues, animal models, and humans. Zalastin hydrochloride nasal solution (nasal spray) is administered as a racemic mixture with no difference in pharmacologic activity noted between the enantiomers in in vitro studies. The major metabolite, desmethylAzelastine, also possesses H1-receptor antagonist activity.
Pharmacodynamics
Cardiac Electrophysiology:
In a placebo-controlled study (95 subjects with allergic rhinitis), there was no evidence of an effect of Zalastin hydrochloride nasal solution (nasal spray) (2 sprays per nostril twice daily for 56 days) on cardiac repolarization as represented by the corrected QT interval (QTc) of the electrocardiogram. Following multiple dose oral administration of Zalastin 4 mg or 8 mg twice daily, the mean change in QTc was 7.2 msec and 3.6 msec, respectively.
Interaction studies investigating the cardiac repolarization effects of concomitantly administered oral Zalastin hydrochloride and erythromycin or ketoconazole were conducted. These drugs had no effect on QTc based on analysis of serial electrocardiograms. At a dose approximately 8 times the maximum recommended dose, Zalastin hydrochloride does not prolong the QTc interval to any clinically relevant extent.
Pharmacokinetics
Absorption: After intranasal administration, the systemic bioavailability of Zalastin hydrochloride is approximately 40%. Maximum plasma concentrations (Cmax) are achieved in 2-3 hours.
Zalastin hydrochloride administered intranasally at doses above two sprays per nostril twice daily for 29 days resulted in greater than proportional increases in Cmax and area under the curve (AUC) for Zalastin.
Distribution: Based on intravenous and oral administration, the steady-state volume of distribution is 14.5 L/kg. In vitro studies with human plasma indicate that the plasma protein binding of Zalastin and its metabolite, desmethylAzelastine, are approximately 88% and 97%, respectively.
Metabolism: Zalastin is oxidatively metabolized to the principal active metabolite, desmethylAzelastine, by the cytochrome P450 enzyme system. The specific P450 isoforms responsible for the biotransformation of Zalastin have not been identified. After intranasal dosing of Zalastin hydrochloride to steady-state, plasma concentrations of desmethylAzelastine range from 20-50% of Zalastin concentrations. Limited data indicate that the metabolite profile is similar when Zalastin hydrochloride is administered via the intranasal or oral route.
Elimination: Based on intravenous and oral administration, the elimination half-life and plasma clearance are 22 hours and 0.5 L/h/kg, respectively. Approximately 75% of an oral dose of radiolabeled Zalastin hydrochloride was excreted in the feces with less than 10% as unchanged Zalastin.
Special Populations:
Hepatic Impairment: Following oral administration, pharmacokinetic parameters were not influenced by hepatic impairment.
Renal Impairment: Based on oral, single-dose studies, renal insufficiency (creatinine clearance <50 mL/min) resulted in a 70-75% higher Cmax and AUC compared to normal subjects. Time to maximum concentration was unchanged.
Age: Following oral administration, pharmacokinetic parameters were not influenced by age.
Gender: Following oral administration, pharmacokinetic parameters were not influenced by gender.
Race: The effect of race has not been evaluated.
Drug-Drug Interactions:
Erythromycin: No significant pharmacokinetic interaction was observed with the co-administration of orally administered Zalastin (4 mg twice daily) with erythromycin (500 mg three times daily for 7 days). In this study, co-administration of orally administered Zalastin with erythromycin resulted in Cmax of 5.36 ± 2.6 ng/mL and AUC of 49.7 ± 24 ng∙h/mL for Zalastin, whereas, administration of Zalastin alone resulted in Cmax of 5.57 ± 2.7 ng/mL and AUC of 48.4 ± 24 ng∙h/mL for Zalastin.
Cimetidine and Ranitidine: In a multiple-dose, steady-state drug interaction trial in healthy subjects, cimetidine (400 mg twice daily) increased orally administered mean Zalastin (4 mg twice daily) concentrations by approximately 65%. No pharmacokinetic interaction was observed with co-administration of orally administered Zalastin (4 mg twice daily) with ranitidine hydrochloride (150 mg twice daily).
Oral co-administration of Zalastin with ranitidine resulted in Cmax of 8.89 ±3.28 ng/mL and AUC of 88.22 ± 40.43 ng∙h/mL for Zalastin, whereas, Zalastin when administered alone resulted in Cmax of 7.83 ± 4.06 ng/mL and AUC of 80.09 ± 43.55 ng∙h/mL for Zalastin.
Theophylline: No significant pharmacokinetic interaction was observed with the co-administration of an oral 4 mg dose of Zalastin hydrochloride twice daily and theophylline 300 mg or 400 mg twice daily.
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References
EPA DSStox. "Azelastine: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).
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