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ACTION AND MECHANISM - Antiallergic. Fexofenadine is the carboxylated metabolite of terfenadine. It is a piperidine derivative that potently, competitively, and specifically blocks H1 receptors, thus prolonging the systemic effects of histamine. Receptor unblocking is very slow, so the antagonism is practically irreversible, depending on the administered dose. It causes vasoconstriction and decreased vascular permeability, reducing the redness and edema associated with allergies. It partially alleviates symptoms associated with allergic processes, such as eye redness and nasal congestion. It also produces a mild bronchodilator effect and reduces skin itching. Clinical experience also suggests that fexofenadine can inhibit the release of histamine from mast cells. Fexofenadine barely crosses the blood-brain barrier, so it has virtually no significant sedative effects. It exhibits high selectivity for H1 receptors and lacks significant anticholinergic effects. Fexofenadine has been shown not to block potassium channels involved in cardiac fiber repolarization, and therefore has no cardiotoxic effects. SPECIAL WARNINGS Due to the anti-allergic effects of this medication, it may produce false negatives in skin tests for hypersensitivity to antigenic extracts. It is recommended to discontinue administration of this medication at least 72 hours before the test. SENIORS No specific problems have been described in the elderly that would require a dosage adjustment. PATIENT ADVICE Take your medication at approximately the same time every day. If you miss a dose, take the next one at the usual time. Do not double a dose to make up for a missed one. CONTRAINDICATIONS - Hypersensitivity to fexofenadine or any component of the medication. Cross-reactions with other antihistamines may occur; therefore, the use of any H1 antihistamine is not recommended in patients who have experienced hypersensitivity to any compound in this group. EFFECTS ON DRIVING It does not appear likely to cause significant effects. However, drowsiness, dizziness, or headache are common. PREGNANCY Animal safety : Fexofinadine was not teratogenic in rats and rabbits (Cp 4-31 times higher than in humans). Administration of 150 mg/kg in rats (Cp 3 times higher than in humans) was associated with decreased birth weight and neonatal survival of offspring. Safety in humans : There are no adequate and well-controlled studies in humans. Its administration is only acceptable if there are no safer therapeutic alternatives, and the benefits outweigh the potential risks. Effects on fertility : No specific studies have been conducted in humans. Fexofenadine did not affect fertility in mice. PHARMACOKINETICS Linear pharmacokinetics at doses up to 120 mg twice daily. At higher doses (240 mg twice daily) the AUC increases by 8.8% above normal. - Absorption: Fexofenadine is rapidly absorbed from the intestine after oral administration. The Cmax obtained after administering a dose of 120 mg and 180 mg is 427 ng/ml and 494 ng/ml, respectively. The Tmax is 2.6 h. The antihistamine effect appears after 1 h, is maximal at 6 h, and lasts for 24 h. Effect of food : Administration of fexofenadine with food may result in a 17% decrease in Cmax, which is not clinically significant. - Distribution: 60-70% binding to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. It is widely distributed throughout tissues, although it does not appear to cross the blood-brain barrier. It is unknown whether it crosses the placenta. Fexofenadine appears to be excreted in breast milk, although the amount eliminated via this route is unknown. Fexofenadine is a substrate of P-gp. - Metabolism: minimal (< 5%), resulting in small amounts of inactive compounds. - Elimination: in feces (80%, mostly unchanged) by biliary excretion. Small amounts (10%) in urine. The t1/2 is 11-15 h. Pharmacokinetics in special situations : - Children: AUC is 56% higher in children aged 7-12 years than in adults. - Elderly: Cmax is 99% higher in those > 65 years old than in those between 19-45 years old. AUC is also higher in elderly patients, but these values are considered within acceptable limits. - Renal insufficiency: in mild to moderate insufficiency (ClCr 41-80 ml/min) and in those with severe renal insufficiency (ClCr 11-40 ml/min) Cmax was 87% and 111% higher respectively, while Clr was 59% and 72% higher, compared with patients with normal renal function. INDICATIONS PRESENTATIONS 120 mg - Relief of symptoms associated with [SEASONAL ALLERGIC RHINITIS] in adults and adolescents from 12 years of age. INTERACTIONS - Antacids. Taking fexofenadine with antacids containing magnesium or aluminum may decrease the absorption of fexofenadine. It is recommended to separate the administration of both medications by at least 2 hours. - Erythromycin and ketoconazole: administering either of these two drugs together with fexofenadine can lead to an organic accumulation of the antihistamine, resulting in toxic effects. - Grapefruit juice: may decrease fexofenadine absorption. - Pollen: a loss of reliability of the diagnostic test with pollen may occur. It is recommended to leave an interval of 2-3 days after the last dose of short-acting antihistamines and 8 weeks with long-acting antihistamines. - Rifampicin: possible decrease in organic levels of fexofenadine and, consequently, in its therapeutic activity. - Cabozantinib: co-administration with P-glycoprotein substrates, including fexofenadine, may result in an increase in adverse reactions. LACTATION Animal safety : no data available. Safety in humans : Fexofenadine is excreted in breast milk, although there are no data regarding the amount of drug excreted. Its administration during breastfeeding is not recommended. CHILDREN Fexofenadine can be used in adolescents from 12 years of age, at the same doses as in adults. Safety and efficacy have not been evaluated in children < 12 years, therefore its use is not recommended. GUIDELINES FOR PROPER ADMINISTRATION Swallow the tablets with water. Administration with food : administer before a meal. POSOLOGY - Adults: 1 tablet, once a day. - Children and adolescents under 18 years of age: * Adolescents aged 12 and over: same as adults. * Children < 12 years: not recommended. - Elderly: no dosage adjustment required. Missed dose : Take the next dose at the usual time. Do not double the next dose. DOSAGE IN HEPATIC INSUFFICIENCY No dosage adjustment is required. DOSAGE IN RENAL INSUFFICIENCY No dosage adjustment is required. PRECAUTIONS - [CARDIAC ARRHYTHMIA]. Antihistamines have been associated with the onset of tachycardia and palpitations. - Limitations in clinical experience. Its efficacy and safety have not been evaluated in patients with renal or hepatic impairment. Although specific dosage recommendations have not been established, caution is advised. ADVERSE REACTIONS Adverse reactions are described according to each frequency interval, being considered very common (>10%), common (1-10%), uncommon (0.1-1%), rare (0.01-0.1%), very rare (<0.01%) or of unknown frequency (cannot be estimated from the available data). - Immune system disorders: frequency unknown [HYPERSENSITIVITY REACTIONS] with manifestations such as [ANGIOEDEMA], [CHEST PRESSURE], [DYSPNEA], [HOT FLASHES] and [ANAPHYLAXIS]. - Psychiatric disorders: frequency unknown [INSOMNIA], [NERVOUSNESS], [SLEEP DISORDERS] or [NIGHTMARES]/excessive dreams ([PARANOIA]). - Nervous system disorders: frequent [HEADACHE], [DROWSY], [DIZZINESS]. - Cardiac disorders: frequency unknown [TACHYCARDIA], [PALPITATIONS]. - Gastrointestinal disorders: frequent [NAUSEA]; frequency unknown [DIARRHEA]. - Skin and subcutaneous tissue disorders: frequency not known [SKIN RASHES], [URTICARIA], [PRURITUS]. - General disorders and administration site conditions: infrequent [FATIGUE]. OVERDOSE Symptoms : Dizziness, drowsiness, fatigue, and dry mouth have been reported following fexofenadine overdose. Single doses of up to 800 mg, and doses of up to 690 mg twice daily for one month or 240 mg once daily for one year have been administered to healthy adults without the development of clinically significant adverse effects compared to placebo. The maximum tolerated dose of fexofenadine has not been established. Measures to be taken : - Antidote: there is no specific antidote. - General elimination measures: standard measures to remove unabsorbed drug. Hemodialysis does not effectively remove fexofenadine from the blood. - Monitoring: monitoring the patient does not appear to be necessary. - Treatment: symptomatic.
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