Progabide is an analog and prodrug of gamma-aminobutyric acid. It is commonly used in the treatment of epilepsy. It has agonistic activity for both the GABAA and GABAB receptors. Progabide has been investigated for many diseases besides epilepsy, including Parkinson's disease, schizophrenia, clinical depression and anxiety disorder with varying success.

Proflavine hemisulfate is an Acridine derivative, which is a slow-acting disinfectant with bacteriostatic action against many Gram-positive bacteria but less effective against Gram-negative organisms. Proflavine Hemisulfate has little antifungal activity.

Procyclidine hydrochloride is a muscarinic antagonist that crosses the blood-brain barrier and is used in the treatment of drug-induced extrapyramidal disorders and in Parkinsonism.

Procaterol hydrochloride is a specific and very potent β2-AR agonist. It acts as a vasodialator for long term treatment of asthma.

Procainamide hydrochloride is the hydrochloride salt preparation of Procainamide, a potent blocker of Na+ channels. Procainamide demonstrates antiarrhythmic effects correlated with blockade of the Na+ channels. Procainamide hydrochloride is an inhibitor of DNA methyltransferase.

Primaquine is an established antimalarial drug used in the treatment of persistent liver forms of P. vivax or P. ovale infection for its ability to kill late-stage gametocytes and hypnozoites. In historical terms, this aminoquinoline was the stimulus for the discovery of glucose-6-phosphate (G6P) dehydrogenase deficiency as it induced hemolytic anemia in patients lacking the G6P-metabolizing enzyme.

Priolocaine Hydrochloride is used as local nerve blocker and for spinal anesthesia. It is a local anesthetic of the amino amide type. Its pharmacological properties are similar to those of lidocaine.

Prednicarbate is a Corticosteroid. The mechanism of action of prednicarbate is as a Corticosteroid Hormone Receptor Agonist. Prednicarbate is a synthetic non-halogenated double-ester derivative of the corticosteroid prednisolone with anti-inflammatory, antipruritic and vasoconstrictive properties. This agent also decreases the number of circulating lymphocytes by suppression of the production of vasodilators such as prostacyclin and nitric oxide.

Pravastatin Sodium is an antilipemic fungal metabolite isolated from cultures of Nocardia autotrophica. It acts as a competitive inhibitor of HMG CoA reductase Pravastatin competitively inhibits hepatic hydroxymethyl-glutaryl coenzyme A reductase, the enzyme which catalyzes the conversion of HMG-CoA to mevalonate, a key step in cholesterol synthesis. This agent lowers plasma cholesterol and lipoprotein levels, and modulates immune responses by suppressing MHC II on interferon gamma-stimulated, antigen-presenting cells such as human vascular endothelial cells.

Practolol is a selective beta blocker that has been used in the emergency treatment of cardiac arrhythmias. Practolol is no longer used as it is highly toxic despite the similarity of its chemical formula to propranolol.

Pivampicillin Hydrochloride is the hydrochloride salt form of an orally active pivalate ester of ampicillin with antibacterial activity. Pivampicillin is hydrolyzed into its active form ampicillin by esterases. Ampicillin binds to and inactivates penicillin-binding proteins (PBPs) located on the inner membrane of the bacterial cell wall. Inactivation of PBPs interferes with the cross-linkage of peptidoglycan chains necessary for bacterial cell wall strength and rigidity. This interrupts bacterial cell wall synthesis and results in the weakening of the bacterial cell wall, eventually causing cell lysis.

Pirbuterol Acetate is a short-acting β2 adrenoreceptor agonist with bronchodilating action used in the treatment of asthma as a breath-activated metered-dose inhaler.

Piperazine is an organic compound that consists of a six-membered ring containing two nitrogen atoms at opposite positions in the ring. Piperazine exists as small alkaline deliquescent crystals with a saline taste. Piperazine exists as small alkaline deliquescent crystals with a saline taste. Piperazine was introduced to medicine as a solvent for uric acid.

Piperacillin sodium is an antibiotic related to penicillin. Piperacillin binds to and inactivates penicillin-binding proteins (PBPs), enzymes located on the inner membrane of the bacterial cell wall, resulting in the weakening of the bacterial cell wall and cell lysis.

Pilocarpine hydrochloride is a slowly hydrolyzed muscarinic agonist with no nicotinic effects. Systemic administration of (+)-pilocarpine is typically used as an animal model for temporal lobe epilepsy and can mimic the generation of complex partial seizures by producing changes in hippocampal neuron morphology, membrane properties, and synaptic responses. Pilocarpine is used as a miotic and in the treatment of glaucoma.

Phensuximide is an anticonvulsant in the succinimide class. It suppresses the paroxysmal three cycle per second spike and wave EEG pattern associated with lapses of consciousness in petit mal seizures. The frequency of attacks is reduced by depression of nerve transmission in the motor cortex.

Perphenazine is a phenothiazine derivative and a dopamine antagonist with antiemetic and antipsychotic properties. Perphenazine blocks postsynaptic dopamine 2(D2) receptors in the mesolimbic and medullary chemoreceptor trigger zone (CTZ), thereby preventing the excess of dopamine in the brain. This leads to reduction in psychotic symptoms, such as hallucinations and delusions.

Permethrin is a widely-used pesticide of the pyrethroid family. Permethrin interacts with voltage-gated Na+ channels and inhibits their natural deactivation, causing the channels to remain open for a long time and destroying equilibrium of the neuronal system. Pyrethroids are also thought to interact with GABA receptors and associated pathways.

Pentamidine isethionate inhibits constitutive NOS1 in the brain and acts as a NMDA Glu antagonist. Pentamidine isethionate is an antimicrobial and neuroprotective agent.

Pentagastrin is a synthetic polypeptide that has effects like gastrin when given parenterally. It stimulates the secretion of gastric acid, pepsin, and intrinsic factor, and has been used as a diagnostic aid as the pentagastrin-stimulated calcitonin test. Pentagastrin binds to the cholecystokinin-B receptor, which is expressed widely in the brain. Activation of these receptors activates the phospholipase C second messenger system.

Penbutolol Sulfate is a medication in the class of beta blockers, used in the treatment of high blood pressure. Penbutolol is able to bind to both beta-1 adrenergic receptors and beta-2 adrenergic receptors, thus making it a non-selective β blocker. Penbutolol is a sympathomimetic drug with properties allowing it to act as a partial agonist at β adrenergic receptors. Penbutolol has also been found to be one of very few compounds that are 5-HT1A antagonists. 5-HT1A receptors are activated by serotonin, which have many different actions in different species. This makes it difficult to create generalizations about serotonin and its effects.

Pefloxacin mesylate dihydrate is a synthetic broad-spectrum fluoroquinolone antibacterial agent active against most gram-negative and gram-positive bacteria.

Paroxetine hydrochloride is a serotonin uptake inhibitor that is effective in the treatment of depression. It is a highly potent and selective ST (serotonin transporter/5-HT) uptake inhibitor. It acts by binding to ST (serotonin transporter/SERT) with high affinity. Paroxetine binds to the pre-synaptic serotonin transporter complex resulting in negative allosteric modulation of the complex thereby blocking reuptake of serotonin by the pre-synaptic transporter. Paroxetine HCl has also displayed a high affinity for muscarinic acetylcholine receptors.

Paramethadione is an anticonvulsant agent in the oxazolidinedione class.

Paramethasone Acetate is a fluorinated glucocorticoid with anti-inflammatory and immunosuppressant properties.

Oxytetracycline Hydrochloride is the hydrochloride salt form of oxytetracycline, a tetracycline derivative produced by Streptomyces rimosus exhibiting antimicrobial activity. Oxytetracycline Hydrochloride is an antibacterial compound isolated from the elaboration products of the actinomycete, Streptomyces rimosus, when grown on a suitable medium. Oxytetracycline hydrochloride interferes with binding of aminoacyl-tRNA to the mRNA-ribosome complex, thereby preventing peptide elongation and inhibiting protein synthesis. It is often used to treat skin conditions.

Oxybutynin is an anticholinergic medication used to relieve urinary and bladder difficulties, including frequent urination and inability to control urination (urge incontinence), by decreasing muscle spasms of the bladder. It is also given to help with symptoms associated with kidney stones.

Oxtriphylline is a cough medicine derived from xanthine that acts as a bronchodilator to open up airways in the lung. Chemically, it is a salt of choline and theophylline. It classifies as an expectorant.

Oxaprozin is a non-steroidal anti-inflammatory drug (NSAID), used to relieve the inflammation, swelling, stiffness, and joint pain associated with osteoarthritis and rheumatoid arthritis. Chemically, it is a propionic acid derivative.

Oxacillin is a narrow-spectrum beta-lactam antibiotic of the penicillin class. It is similar to methicillin, and has replaced methicillin in clinical use. Other related compounds are nafcillin, cloxacillin, dicloxacillin, and flucloxacillin. Since it is resistant to penicillinase enzymes, such as that produced by Staphylococcus aureus, it is widely used clinically in the US to treat penicillin-resistant Staphylococcus aureus.