Human health and medicine

Pharyngeal reflex

Pharyngeal reflex (gag reflex): involuntary throat contraction protecting the airway, mediated by CN IX afferent and CN X efferent limbs; poorly predictive of dysphagia despite traditional bedside use.

Pharyngeal-cervical-brachial variant of Guillain-Barré syndrome

Pharyngeal-cervical-brachial (PCB) variant of Guillain-Barré syndrome, also called PCB-GBS: a rare localized axonal GBS subtype causing oropharyngeal, neck, and arm weakness with areflexia, linked to anti-GT1a IgG antibodies.

Pharyngectomy

Pharyngectomy: surgical removal of all or part of the pharynx (throat), mainly for throat cancer; ranges from oropharyngectomy to circumferential pharyngolaryngectomy with flap reconstruction.

Pharyngitis

Pharyngitis, inflammation of the pharynx causing sore throat, is mostly viral (about 80% of cases); group A streptococcus causes 20-30% of pediatric and 5-15% of adult cases, diagnosed by Centor criteria, RADT, or throat culture, and treated with penicillin.

Pharyngoplasty

Pharyngoplasty is surgery on the soft palate and pharyngeal walls, with variants that enlarge the velopharynx to treat sleep apnea or narrow it to correct velopharyngeal insufficiency.

Pharyngostomy

Pharyngostomy: surgical creation of an external opening into the pharynx for feeding, drainage, or salivary diversion; an alternative to nasogastric tubes now largely displaced by gastrostomy.

Pharynx

Pharynx (throat): funnel-shaped muscular tube from skull base to C6, shared by digestive and respiratory tracts, divided into nasopharynx, oropharynx, and laryngopharynx; constrictor muscles, vagus and glossopharyngeal innervation, pharyngeal arch embryology.

Phase I/II trial

A Phase I/II trial is a clinical trial design that combines dose escalation and safety evaluation with early evidence of treatment efficacy, aiming to find the optimal biological dose.

Phase II/III trial

A Phase II/III trial, often called a seamless or adaptive seamless design, combines Phase II and Phase III objectives in one protocol, selecting doses at an interim analysis while controlling type I error.

Phase IV trial

A Phase IV trial, also called Phase 4, is a study of a drug after marketing approval, measuring safety, effectiveness, and optimal use in broader patient populations.

Oct 22, 2026

Phase-change perfluorocarbon nanodroplets

Phase-change perfluorocarbon nanodroplets (PFCnDs) are submicrometer liquid perfluorocarbon particles that ultrasound or laser light converts into gas microbubbles, enabling on-demand contrast imaging and drug delivery.

Phase-contrast magnetic resonance imaging

Phase-contrast magnetic resonance imaging, also known as phase-contrast MRI, is an MRI technique that measures blood flow noninvasively by encoding fluid velocity into the signal phase.

Phase–amplitude coupling

Phase–amplitude coupling (PAC) is a signal-analysis method quantifying how the amplitude of fast neural oscillations is modulated by the phase of slower ones, used to study cognition and diseases like Parkinson's.

Phases of clinical research

Phases of clinical research: the staged testing of new drugs and health products in humans, from Phase 0 microdosing (10–15 people, <100 micrograms) through Phase I safety (20–100), Phase II dosing, Phase III pivotal trials, to Phase IV post-marketing surveillance.

Phelan-McDermid syndrome

Phelan-McDermid syndrome, or 22q13.3 deletion syndrome, is a rare neurodevelopmental disorder caused by SHANK3 haploinsufficiency, featuring developmental delay, absent speech, hypotonia, and autism spectrum disorder.

Phenacemide

Phenacemide (Phenurone), phenylacetylurea, a 1948 ureide anticonvulsant for refractory psychomotor epilepsy, FDA-approved 1951, withdrawn 2004 due to liver and bone marrow toxicity.

Phenazopyridine

Phenazopyridine (Pyridium, AZO) is an azo-dye urinary analgesic for dysuria, not an antibiotic. Dosed 200 mg three times daily, limited to 2 days; risks include methemoglobinemia and renal or hepatic toxicity.

Phencyclidine

Phencyclidine (PCP, angel dust), 1-(1-phenylcyclohexyl)piperidine, is a dissociative anesthetic and NMDA receptor antagonist synthesized in 1956, abandoned for human use, now a Schedule II drug of abuse.

Phendimetrazine

Phendimetrazine (Bontril PDM, Plegine) is a DEA Schedule III sympathomimetic anorectic, FDA-approved since 1959/1960 for short-term obesity treatment with caloric restriction; 35 mg tablets, tolerance within weeks, over 3 million US prescriptions 2008-2011.

Phenelzine

Phenelzine (Nardil) is an irreversible, nonselective MAO-A/MAO-B inhibitor antidepressant, a hydrazine derivative available since 1960, used mainly for atypical depression, with tyramine dietary restrictions and hypertensive crisis risk.

Phenibut (Фенибут)

Phenibut (Фенибут, fenibut, PhGABA, β-phenyl-γ-aminobutyric acid) is a Russian-developed 1960s GABA_B agonist anxiolytic, not FDA-approved in the US, sold online as a nootropic, with dependence, overdose, and severe withdrawal risks.

Phenicarbazide

Phenicarbazide (1-phenylsemicarbazide, anilinourea, Kryogenin), C7H9N3O, CAS 103-03-7: a phenylhydrazine urea derivative, former INN drug (withdrawn), IARC Group 3, GHS harmful/irritant, found in Heimia plants.

Oct 15, 2026

Phenindione

Phenindione is an oral anticoagulant of the indandione class that acts as a vitamin K antagonist, similar to warfarin but now rarely used because of hypersensitivity reactions.

Pheniramine

Pheniramine (pheniramine maleate, Avil) is a first-generation alkylamine H1 antihistamine, FDA approved in 1948, used for allergy, hay fever, colds, motion sickness, and allergic conjunctivitis eye drops; largely supplanted by second-generation antihistamines.