Montelukast
Absorption: is quickly absorbed following administration by the oral route
Volume of distribution: 8 to 11 litres
Protein binding: 99%
Half life: 2.7-5.5 hours
Metabolism: highly metabolized and typically so by the cytochrome P450, 3A4, 2C8, and 2C9 isoenzymes.
Excretion: about 86% of Montelukast and its metabolites are almost exclusively excreted in the bile and into the feces.

Levocetirizine
Absorption: rapidly and extensively absorbed following oral administration. In adults, peak plasma concentrations are achieved 0.9 hour after administration of the oral tablet
Volume of distribution: approximately 0.4 L/kg
Protein binding: 91-92%
Metabolism: poorly metabolized and mostly excreted via the urine
Route of elimination: renal excretion
Half life: 8-9 hours
Clearance: 0.63 mL/kg/min

PHARMACODYNAMICS
Montelukast
Montelukast is a highly selective leukotriene receptor antagonist that binds with high affinity to the cysteinyl leukotriene receptor for leukotrienes D4 and E4 which inhibits leukotriene physiologic effects (such as airway edema, smooth muscle contraction and impairment of normal cellular activity).

Levocetirizine
Levocetirizine is the active enantiomer of cetirizine. It's principal effects are mediated via selective inhibition of H1 receptors.

- Seasonal and perennial allergic rhinitis
- Allergic dermatitis
- Chronic urticaria
- Atopic eczema
- Excercise- induced asthma
- Add on therapy to chronic persistent asthma

DOSAGE
This medication is taken orally with or without food usually once daily in the evening.

Montelukast
Skin rash, mood changes, tremors, headache, stomach pain, heart burn, upset stomach, nausea, diarrhoea, tooth pain, tiredness, fever, stuffy nose, sore throat, cough & hoarseness.

Levocetirizine
Dry mouth, fatigue, runny or stuffy nose, sore throat, central nervous system depression, drowsiness, sedation, dizziness, insomnia, blurred vision, impotence, hypertension, wheezing, sweating, ECG changes & tinnitus.

Montelukast should not be used during sudden asthma attack, to treat status asthmaticus. It should not be used in place of inhaled/ oral corticosteroids. This drug also may increase risk of mental health problems.

Levocetirizine should not be used if you are allergic to any of its ingredient and should be kept out of the reach of children.