XERIN

Indications

• Prophylaxis of asthma
• Management of seasonal allergic rhinitis
• Symptomatic relief of seasonal allergic rhinitis in patients with asthma

Dosage

Adults: 10 mg once daily, taken in the evening.

Mechanism of action

Montelukast binds with high affinity and selectivity to the cysteinyl leukotriene receptor type-1 (CysLT1). This action inhibits the physiological effects of cysteinyl leukotrienes (like LTC4, LTD4, and LTE4), which include bronchoconstriction, mucus secretion, and eosinophil recruitment. By blocking these receptors, montelukast effectively reduces the bronchoconstriction and other symptoms associated with asthma and allergic rhinitis.

Pharmacodynamics

Montelukast exhibits significant affinity for the CysLT1 receptor, preferentially blocking the effects of leukotriene LTD4 at doses as low as 5 mg. Clinical studies have shown that montelukast can inhibit both early and late phase bronchoconstriction due to antigen exposure by approximately 75% and 57%, respectively. The onset of bronchodilation can occur within 2 hours of oral administration, and its effects can be additive when used with beta agonists. However, doses above 10 mg daily do not provide additional clinical benefits in adults.

Pharmacokinetics

Montelukast is well absorbed following oral administration, with peak plasma concentrations occurring within 3 to 4 hours. It is extensively metabolized in the liver, primarily via cytochrome P450 enzymes. The half-life of montelukast is approximately 2.7 to 5.5 hours, allowing for once-daily dosing. It is eliminated via bile, with a small percentage excreted unchanged in urine. Special populations, such as those with hepatic impairment, may require caution, although specific dosage adjustments have not been established.

Adverse effects

• Headache
• Abdominal pain
• Dizziness
• Fatigue
• Nausea
• Rash
• Changes in mood or behavior
• Sleep disturbances

Interactions

• Opicapone: Severe (increases exposure)
• Selpercatinib: Severe (increases exposure)
• Deferasirox: Unknown (increases exposure)
• Leflunomide: Unknown (increases exposure)
• Mifepristone: Unknown (increases exposure)
• Mitotane: Unknown (decreases exposure)
• Teriflunomide: Unknown (increases exposure)
• Rifampicin: Unknown (decreases exposure)

Precautions

• Caution in patients with hepatic impairment
• Use with caution in patients with renal impairment
• Consider risk of mood changes and behavioral side effects

Pregnancy

Manufacturer advises to avoid use during pregnancy due to limited information available.

Breast-feeding

Manufacturer advises to avoid during breastfeeding, especially in the first few days after birth due to potential transfer of antibodies to the infant.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Tablets: 10 mg (adults and children over 15 years)
• Chewable tablets: 5 mg (children 6–14 years)
• Granules: 4 mg (children 6 months–5 years)

Indications

• Seasonal allergic rhinitis
• Chronic idiopathic urticaria

Dosage

Children: For children aged 6 to 11 years, the dose is 30 mg twice daily. For children aged 12 to 17 years, the dose is 120 mg once daily.

Adults: For adults, the recommended dose is 180 mg once daily.

Mechanism of action

Levocetirizine is an active enantiomer of cetirizine and functions as a selective antagonist of the peripheral H1 receptor. By blocking the action of histamine, a key mediator in allergic responses, it reduces symptoms such as sneezing, itching, and runny nose. It also prevents the activation of sensory neurons, thereby mitigating pruritus and swelling associated with allergic reactions.

Pharmacodynamics

Levocetirizine exhibits antihistaminic effects with a rapid onset of action. Its affinity for peripheral H1 receptors allows it to effectively reduce the symptoms of allergic rhinitis and urticaria. While it is termed 'non-sedating', some degree of sedation may still occur in sensitive individuals, although this is generally minimal compared to first-generation antihistamines.

Pharmacokinetics

Levocetirizine is well absorbed after oral administration, with peak plasma concentrations typically reached within 0.9 hours. The drug has a volume of distribution of approximately 0.4 L/kg and is primarily excreted unchanged in urine. It has a half-life of about 8 hours, allowing for once-daily dosing. In patients with renal impairment, dose adjustments may be necessary due to altered drug clearance.

Contra-indications

• Acute porphyrias

Adverse effects

• Asthenia
• Constipation
• Drowsiness
• Dry mouth
• Abdominal pain
• Aggression
• Agitation
• Angioedema
• Appetite increased
• Arthralgia
• Depression
• Diarrhoea
• Dizziness
• Fatigue
• Hallucination
• Hepatitis
• Myalgia
• Nausea
• Oedema
• Palpitations
• Paraesthesia
• Seizure
• Skin reactions
• Sleep disorders
• Suicidal ideation
• Syncope
• Tachycardia
• Taste altered
• Tremor
• Urinary disorders
• Vertigo
• Vision disorders
• Vomiting
• Weight increased

Interactions

• Other antihistamines
• Alcohol (may increase sedation)
• CNS depressants

Precautions

• Caution in renal impairment
• Patients should be advised about potential drowsiness affecting driving and skilled tasks

Pregnancy

Most manufacturers of antihistamines advise avoiding their use during pregnancy; however, there is no evidence of teratogenicity.

Breast-feeding

Most antihistamines are present in breast milk in varying amounts; although not known to be harmful, most manufacturers advise avoiding their use in mothers who are breastfeeding.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Oral suspension
• Oral solution
• Tablets

Indications

• Allergic rhinitis
• Chronic urticaria

Dosage

Children: For children aged 6 to 11 years, the recommended dose is 5 mg once daily. For children aged 2 to 5 years, the dose is 1.25 mg once daily.

Adults: The usual dose for adults is 5 mg once daily.

Mechanism of action

Levocetirizine selectively inhibits histamine H1 receptors. This action prevents histamine from activating the receptor and causing effects such as smooth muscle contraction, increased permeability of vascular endothelium, histidine uptake in basophils, stimulation of cough receptors, and stimulation of flare responses in the nervous system.

Pharmacodynamics

As a second-generation histamine H1 antagonist, levocetirizine effectively reduces various allergic symptoms. It possesses a long duration of action, allowing for once-daily dosing. The therapeutic index is favorable, with studies showing that the maximal nonlethal dose is significantly higher than the therapeutic dose. Caution is advised for activities requiring full alertness and in patients predisposed to urinary retention.

Pharmacokinetics

Levocetirizine is well absorbed after oral administration, with peak plasma concentrations typically reached within approximately 1 hour. It has a volume of distribution of about 0.4 L/kg and is primarily excreted unchanged in the urine. The elimination half-life is approximately 8 to 9 hours, allowing for once-daily dosing.

Contra-indications

• Hypersensitivity to levocetirizine or any of its components
• Severe renal impairment

Adverse effects

• Drowsiness
• Fatigue
• Dry mouth
• Headache
• Gastrointestinal disturbances

Interactions

• CNS depressants may enhance sedative effects
• Alcohol may increase sedation

Precautions

• Caution in patients with a history of urinary retention
• Caution in patients with severe renal impairment
• Avoid operating machinery or driving until you know how levocetirizine affects you

Pregnancy

Levocetirizine should be used in pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Levocetirizine is excreted in breast milk; caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Tablets
• Oral solution

Mechanism of action

Cysteinyl leukotrienes (CysLT) like LTC4, LTD4, and LTE4, among others, are eicosanoids released by a variety of cells like mast cells and eosinophils. When such CysLT bind to corresponding CysLT receptors like CysLT type-1 receptors located on respiratory airway smooth muscle cells, airway macrophages, and on various pro-inflammatory cells like eosinophils and some specific myeloid stem cells activities that facilitate the pathophysiology of asthma and allergic rhinitis are stimulated. In particular, CysLT-mediated airway bronchoconstriction, occluding mucous secretion, vascular permeability, and eosinophil recruitment are all types of effects that facilitate asthma. Alternatively, in allergic rhinitis, CysLTs are released by the nasal mucosa when exposed to allergens during both early and late phase reactions and participate in eliciting symptoms of allergic rhinitis like a congested nose and airway. Subsequently, montelukast is a leukotriene receptor antagonist that binds with high affinity and selectivity to the CysLT type 1 receptor, which consequently assists in inhibiting any physiological actions of CysLTs like LTC4, LTD4, and LTE4 at the receptor that may facilitate asthma or allergic rhinitis. Montelukast inhibits bronchoconstriction due to antigen challenge. Montelukast is a selective leukotriene receptor antagonist of the cysteinyl leukotriene CysLT1 receptor. The cysteinyl leukotrienes (LTC4 , LTD4, LTE4) are products of arachidonic acid metabolism that are released from various cells, including mast cells and eosinophils. They bind to cysteinyl leukotriene receptors (CysLT) found in the human airway. Binding of cysteinyl leukotrienes to leukotriene receptors has been correlated with the pathophysiology of asthma, including airway edema, smooth muscle contraction, and altered cellular activity associated with the inflammatory process, factors that contribute to the signs and symptoms of asthma. Montelukast binding to the CysLT1, receptor is high-affinity and selective, preferring the CysLT1 receptor to other pharmacologically important airway receptors, such as the prostanoid, cholinergic, or beta-adrenergic receptor. Montelukcast inhibits physiologic actions of LTD4 at the CysLT1 receptors, without any agonist activity. Because of the role of leukotrienes in the pathogenesis of asthma, modification of leukotriene activity may be used to reduce airway symptoms, decrease bronchial smooth muscle tone, and improve asthma control. Inhibition of leukotriene-mediated effects may be achieved by drugs that interrupt 5-lipoxygenase activity and prevent formation of leukotrienes (e.g., zileuton) or by antagonism of leukotriene activity at specific receptor sites in the airway (e.g., montelukast, zafirlukast). The antagonist activity of montelukast is selective, competitive, and reversible. Montelukast competitively inhibits the action of LTD4 at a subgroup of CysLT receptors (CysLT1) in airway smooth muscle. In vitro, montelukast possesses affinity for the CysLT1 receptor that is similar to that of LTD4. In in vitro studies, montelukast antagonized contraction of isolated animal smooth muscle produced by LTD4, but did not antagonize contraction produced by LTC4. In animal studies, montelukast antagonized contraction of airway smooth muscle produced by LTD4 or antigen.

Pharmacodynamics

Montelukast is a leukotriene receptor antagonist that demonstrates a marked affinity and selectivity to the cysteinyl leukotriene receptor type-1 in preference to many other crucial airway receptors like the prostanoid, cholinergic, or beta-adrenergic receptors. As a consequence, the agent can elicit substantial blockage of LTD4 leukotriene-mediated bronchoconstriction with doses as low as 5 mg. Moreover, a placebo-controlled, crossover study (n=12) demonstrated that montelukast is capable of inhibiting early and late phase bronchoconstriction caused by antigen challenge by 75% and 57% respectively. In particular, it has been documented that montelukast can cause bronchodilation as soon as within 2 hours of oral administration. This action can also be additive to the bronchodilation caused by the concomitant use of a beta agonist. Nevertheless, clinical investigations performed with adults 15 years of age and older revealed that no additional clinical benefit is obtained when doses of montelukast greater than 10 mg a day are used. Additionally, in clinical trials with adults and pediatric asthmatic patients aged 6 to 14 years, it was also determined that montelukast can reduce mean peripheral blood eosinophils by about 13% to 15% from baseline in comparison to placebo during double-blind treatment periods. At the same time, in patients aged 15 years and older who were experiencing seasonal allergic rhinitis, the use of montelukast caused a median reduction of 13% in peripheral blood eosinophil counts when compared to placebo as well.

Mechanism of action

Levocetirizine selectively inhibits histamine H₁ receptors. This action prevents histamine from activating this receptor and causing effects like smooth muscle contraction, increased permeability of vascular endothelium, histidine uptake in basophils, stimulation of cough receptors, and stimulation of flare responses in the nervous system.

Pharmacodynamics

Levocetirizine is a second generation histamine H₁ antagonist used to treat various allergic symptoms. It has a long duration of action as it is generally taken once daily, and a wide therapeutic window as animal studies show the maximal nonlethal dose is over 100x a normal dose. Patients are cautioned to avoid tasks that require complete alertness, avoid alertness, and use caution in patients with factors predisposing urinary retention.