Gefapix45 mg

Gefapix is indicated for the treatment of refractory or unexplained chronic cough in adults. This includes:

• Refractory chronic cough: Chronic cough (lasting more than 8 weeks) that persists despite guideline-based treatment of an identifiable underlying condition (e.g. asthma, gastro-oesophageal reflux disease, upper airway cough syndrome).
• Unexplained chronic cough: Chronic cough for which no underlying cause can be identified despite a thorough diagnostic work-up.

Gefapix is an established, guideline-supported treatment option specifically for this indication and is not intended for acute cough due to common cold, other short-term respiratory infections, or cough with a treatable identified cause that has not yet been adequately managed. It is not an antibiotic and has no role in treating infections.

Each film-coated tablet contains Gefapixant Citrate equivalent to 45 mg of gefapixant base, along with pharmaceutically acceptable excipients that ensure tablet stability and controlled release. Strength and formulation may vary by manufacturer; always check the product label for exact composition.

Gefapix is an orally administered, non-narcotic, non-opioid medicine belonging to a novel class of cough therapeutics called P2X3 receptor antagonists. It was specifically developed to address chronic cough that does not respond to treatment of an underlying cause, or for which no cause can be found, filling an important treatment gap since most traditional antitussives are not effective or approved for this population.

Gefapix works by selectively blocking overactive signalling in the airway sensory nerves that drive the persistent urge to cough, rather than by suppressing the central cough reflex or by any anti-inflammatory or antimicrobial mechanism.

Gefapix belongs to the therapeutic class of antitussives (cough suppressants), specifically P2X3 receptor antagonists — a distinct pharmacological category from opioid-based, antihistamine-based, or mucolytic cough medicines.

Mechanism of Action

Gefapixant Citrate is a selective antagonist of the P2X3 receptor, an ATP-gated ion channel expressed on vagal sensory (C-fibre) nerve endings in the airways. In chronic cough, these nerves become hypersensitised, and ATP released from airway tissue activates P2X3 receptors, triggering excessive and inappropriate cough signals to the brain. By blocking ATP-mediated activation of these P2X3 receptors, Gefapixant Citrate reduces this hypersensitivity and decreases cough frequency and severity without depressing the central nervous system or respiratory drive.

Pharmacokinetics

Gefapixant Citrate is well absorbed after oral administration, undergoes minor hepatic metabolism, and is eliminated primarily via renal excretion, largely as unchanged drug. Because hepatic metabolism is a minor elimination pathway, hepatic impairment has limited effect on drug exposure, whereas renal function significantly affects clearance.

Gefapix tablets should be swallowed whole with a glass of water, with or without food, at approximately the same times each day to maintain consistent blood levels. Do not crush, chew, or split the tablet unless specifically advised by a physician or pharmacist. If a dose is missed, take it as soon as remembered unless it is close to the next scheduled dose, in which case the missed dose should be skipped — do not double the dose.

Formal drug-interaction studies with Gefapix have not identified any clinically meaningful pharmacokinetic interactions, as hepatic metabolism via cytochrome P450 and UGT enzymes is a minor elimination pathway and transporter-mediated interactions observed in vitro have not translated into clinically significant effects in vivo.

As a precaution, patients should inform their physician of all prescription medicines, over-the-counter products, and herbal supplements they are taking, particularly other drugs affecting renal clearance, before starting Gefapix, so that the physician can assess the overall clinical picture.

The most common adverse effect of Gefapix is taste disturbance (dysgeusia), reported very commonly and described by patients as a bitter, metallic, or salty taste; related complaints of reduced taste (hypogeusia) or complete loss of taste (ageusia) also occur. Taste disturbance is the leading reason patients discontinue treatment and typically resolves within about 5 days of stopping the medicine, although rare cases of prolonged taste changes lasting beyond a year have been reported.

Very Common (may affect more than 1 in 10 people)

• Dysgeusia, hypogeusia, ageusia (taste disturbance/loss)

Common (may affect up to 1 in 10 people)

• Nausea
• Dry mouth
• Diarrhoea, upper abdominal pain, dyspepsia (indigestion)
• Headache and dizziness
• Insomnia
• Cough exacerbation, oropharyngeal (throat) pain
• Upper respiratory tract infection
• Decreased appetite

Uncommon

• Urinary tract, kidney, or bladder calculi (stones)

Patients should contact their physician if side effects are severe, persistent, or bothersome, particularly if taste disturbance affects appetite, nutrition, or quality of life.

Pregnancy: Data on the use of Gefapix in pregnant women are limited. As a precaution, it is preferable to avoid Gefapix during pregnancy and in women of childbearing potential who are not using effective contraception. Gefapix should be used during pregnancy only if clearly needed and if the potential benefit to the mother justifies the potential risk to the fetus; a physician should always be consulted before use in pregnancy.

Lactation: Available data indicate that gefapixant is excreted into milk in animal studies, and a risk to the breastfeeding infant cannot be excluded. A decision should be made, in consultation with a physician, whether to discontinue breastfeeding or discontinue Gefapix therapy, taking into account the benefit of breastfeeding for the child and the benefit of therapy for the mother.

• Taste disturbance: Very commonly reported; see Side Effects for details. Patients should be counselled about this possibility before starting treatment.
• Obstructive sleep apnoea (OSA): Higher doses of Gefapix have been associated with reduced oxygen saturation during sleep in some patients. Suspected or diagnosed OSA should be appropriately managed before and during Gefapix therapy.
• Sulfonamide sensitivity: Gefapix contains a sulfonamide-like chemical structure; although cross-reactivity has not been established, it should be used with caution in patients with a history of sulfonamide allergy, with clinical judgement applied.
• Acute lower respiratory tract infection: Cough due to an acute lower respiratory infection should be evaluated and treated appropriately; use of Gefapix in this setting should be individualised.
• Renal impairment: Dose adjustment is required in severe renal impairment (see Dosage and Administration); data are insufficient in end-stage renal disease on dialysis.
• Gefapix does not treat the underlying cause of cough and should be used only after appropriate diagnostic evaluation, under medical supervision.

In cases of known or suspected overdose with Gefapix, seek immediate medical attention or contact a poison control centre / emergency services without delay. In clinical studies, doses substantially higher than the recommended dose were associated with crystalluria (crystals in urine) without evidence of kidney injury; no other serious adverse events have been reported with overdose. Management of overdose should be supportive and symptomatic, and gefapixant is partially removed by haemodialysis. Do not attempt to manage a suspected overdose at home without professional medical guidance.

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Elderly

No overall differences in safety or efficacy have been identified between elderly and younger adult patients; no dose adjustment is required based on age alone, though renal function should be assessed as it commonly declines with age.

Renal Impairment

No dose adjustment is needed for mild-to-moderate renal impairment. In severe renal impairment, the dose of Gefapix should be reduced to once daily. Data are insufficient to recommend use in end-stage renal disease requiring dialysis.

Hepatic Impairment

No dose adjustment of Gefapix is required in patients with hepatic impairment of any severity, as hepatic metabolism is a minor route of elimination.

Pediatric Population

The safety and efficacy of Gefapix in children and adolescents below 18 years of age have not been established; see Pediatric Use.

The duration of treatment with Gefapix should be determined by the prescribing physician based on clinical response and tolerability. Chronic cough is typically a long-term condition, and treatment may be continued as long as it remains effective and well tolerated; the physician should periodically reassess the ongoing need for therapy. Patients should not stop or continue treatment on their own without medical advice.

Antitussive; P2X3 receptor antagonist.

Gefapixant Citrate selectively blocks the P2X3 receptor, an ATP-gated ion channel on airway sensory nerve fibres, thereby reducing ATP-mediated activation of the hypersensitive cough reflex pathway that underlies chronic refractory or unexplained cough.

The safety and efficacy of Gefapix in pediatric patients under 18 years of age have not been established, and there is currently no relevant approved use of Gefapix in this population. Gefapix should not be used in children or adolescents outside of a clinical trial setting unless specifically directed by a specialist physician.