VALOID ADULT

Indications

• Postoperative nausea and vomiting
• Motion sickness
• Vertigo associated with labyrinth disorders

Dosage

Children: For children aged 1 month to 5 years: 0.5–1 mg/kg up to 3 times a day (maximum per dose 25 mg). For children aged 6 to 11 years: 25 mg up to 3 times a day. For children aged 12 to 17

Adults: 50 mg up to 3 times a day, administered by mouth or intravenous injection over 3-5 minutes.

Mechanism of action

Cyclizine acts by blocking histamine H1 receptors in the vomiting center of the brain, specifically the chemoreceptor trigger zone (CTZ). It also inhibits muscarinic cholinergic receptors, which are involved in the transmission of signals from the vestibular apparatus to the vomiting center. This dual action helps to alleviate nausea and vomiting by dampening the overstimulation of these pathways, particularly in cases of motion sickness.

Pharmacodynamics

Cyclizine exhibits antiemetic and antivertigo effects through its central anticholinergic properties, which help to depress labyrinth excitability and vestibular stimulation. It has antihistaminic properties that contribute to its effectiveness in managing nausea and vomiting. The drug also possesses CNS depressant effects, which can enhance its efficacy in treating symptoms of motion sickness and vertigo.

Pharmacokinetics

Cyclizine is well absorbed after oral administration, with peak plasma concentrations usually occurring within 1 to 2 hours. It is extensively metabolized in the liver, and its elimination half-life ranges from 20 to 30 hours. The drug is primarily excreted in urine as metabolites. Factors such as age, liver function, and concurrent medications can influence its pharmacokinetic profile.

Adverse effects

• Drowsiness
• Dry mouth
• Blurred vision
• Constipation
• Urinary retention
• Tachycardia
• Dizziness

Interactions

• Alcohol may enhance sedative effects
• CNS depressants may increase sedation
• Anticholinergic drugs may enhance adverse effects

Precautions

• Caution in patients with glaucoma
• Caution in patients with prostate hypertrophy
• Avoid in patients with severe liver disease

Pregnancy

Cyclizine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Consult healthcare professionals.

Breast-feeding

Cyclizine is excreted in breast milk; caution is advised when administering to nursing mothers.

Storage

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

Formulations

• Tablets
• Injection

Mechanism of action

Vomiting (emesis) is essentially a protective mechanism for removing irritant or otherwise harmful substances from the upper GI tract. Emesis or vomiting is controlled by the vomiting centre in the medulla region of the brain, an important part of which is the chemotrigger zone (CTZ). The vomiting centre possesses neurons which are rich in muscarinic cholinergic and histamine containing synapses. These types of neurons are especially involved in transmission from the vestibular apparatus to the vomiting centre. Motion sickness principally involves overstimulation of these pathways due to various sensory stimuli. Hence the action of cyclizine which acts to block the histamine receptors in the vomiting centre and thus reduce activity along these pathways. Furthermore since cyclizine possesses anti-cholinergic properties as well, the muscarinic receptors are similarly blocked. .../IT SEEMS/ THAT STIMULATION OF VESTIBULAR APPARATUS IS NECESSARY & SUFFICIENT...& THAT VESTIBULAR CEREBELLAR MIDBRAIN "INTEGRATIVE VOMITING CENTER" & MEDULLARY CHEMORECEPTIVE TRIGGER ZONE ARE...INVOLVED /IN MOTION SICKNESS/. IT IS...PROBABLE THAT EFFECTIVE ANTIHISTAMINES EXERT.../ACTION/ IN THESE CENTERS. /ANTIHISTAMINE/

Pharmacodynamics

Cyclizine is a piperazine-derivative antihistamine used as an antivertigo/antiemetic agent. Cyclizine is used in the prevention and treatment of nausea, vomiting, and dizziness associated with motion sickness. Additionally, it has been used in the management of vertigo in diseases affecting the vestibular apparatus. Although the mechanism by which cyclizine exerts its antiemetic and antivertigo effects has not been fully elucidated, its central anticholinergic properties are partially responsible. The drug depresses labyrinth excitability and vestibular stimulation, and it may affect the medullary chemoreceptor trigger zone. It also possesses anticholinergic, antihistaminic, central nervous system depressant, and local anesthetic effects.