Cosyntropin (ACTH (1–24)) is a synthetic peptide that is identical to the 24-amino acid segment at the N-terminal of adrenocorticotropic hormone. It is intended for use as a diagnostic agent in the screening of patients presumed to have adrenocortical insufficiency. Cosyntropin may bind to sites located on the adrenergic nerve endings associated with the cardiac tissue, and such binding would interfere with the neuronal reuptake of the catecholamines

Glucagon is a polypeptide hormone identical to human glucagon that increases blood glucose and relaxes smooth muscle of the gastrointestinal tract. Glucagon is synthesized in a special non-pathogenic laboratory strain of Escherichia coli bacteria that has been genetically altered by the addition of the gene for glucagon. Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis. Glucagon also decreases fatty acid synthesis in adipose tissue and the liver, as well as promoting lipolysis in these tissues, which causes them to release fatty acids into circulation where they can be catabolised to generate energy in tissues such as skeletal muscle when required. Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan (a polymer made up of glucose molecules). Liver cells (hepatocytes) have glucagon receptors. When glucagon binds to the glucagon receptors, the liver cells convert the glycogen into individual glucose molecules and release them into the bloodstream, in a process known as glycogenolysis. As these stores become depleted, glucagon then encourages the liver and kidney to synthesize additional glucose by gluconeogenesis. Glucagon turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis. Glucagon also regulates the rate of glucose production through lipolysis. Glucagon induces lipolysis in humans under conditions of insulin suppression (such as diabetes mellitus type 1). Glucagon increases blood glucose concentration and is used in the treatment of hypoglycemia. Glucagon administered through a parenteral route relaxes smooth muscle of the stomach, duodenum, small bowel, and colon. Glucagon is also indicated as a diagnostic aid in the radiologic examination of the stomach, duodenum, small bowel, and colon when diminished intestinal motility would be advantageous.

Corticotropin is a polypeptide hormone produced and secreted by the pituitary gland. Corticotropin acts through the stimulation of cell surface the adrenocorticotropic hormone (ACTH) receptors, which are primarily located on the adrenocortical cells. Corticotropin stimulates the cortex of the adrenal gland and boosts the synthesis of corticosteroids, mainly glucocorticoids but also sex steroids (androgens). Corticotropin is indicated as monotherapy for the treatment of exacerbations of multiple sclerosis in adults and infantile spasms in infants and children under 2 years of age. Controlled clinical trials have shown Corticotropin to be effective in speeding the resolution of acute exacerbations of multiple sclerosis. However, there is no evidence that it affects the ultimate outcome or natural history of the disease. The mechanism of action of Corticotropin in the treatment of infantile spasms is unknown.

Argipressin is a neurohypophysial hormone from the vasopressin hormone family. Its two primary functions are to retain water in the body and to constrict blood vessels. The antidiuretic action of Argipressin is ascribed to increase in reabsorption of water by the renal tubules. Argipressin can cause contraction of smooth muscle of the gastrointestinal tract, gall bladder, urinary bladder and all parts of the vascular bed, especially the capillaries, small arterioles and venules with less effect on the smooth musculature of the large veins. Agripressin for injections is used for use in diabetes insipidus, when this is not of nephrogenic origin and control of bleeding from oesophageal varices. In addition, argipressin is indicated to increase blood pressure in adults with vasodilatory shock (e.g., post-cardiotomy or sepsis) who remain hypotensive despite fluids and catecholamines.

More than a century ago, Sir Henry Dale demonstrated that a component of the pituitary causes contractions of the mammalian uterus, hence his coining the term “oxytocic,” derived from the Greek for “quick birth,” for its activity. The discovery that a component of the pituitary causes milk secretion followed within a few years. By 1930, oxytocin was separated from vasopressin into pitocin and pitressin, respectively, at Parke Davis and made available for research. That a single peptide was responsible for these uterine and mammary actions was definitively confirmed upon the sequencing and synthesis of the peptide, 9 amino acids in length. Vincent du Vigneaud was awarded a Nobel Prize for this work. Oxytocin is indicated for the initiation or improvement of uterine contractions, where this is desirable and considered suitable for reasons of fetal or maternal concern, in order to achieve vaginal delivery. Oxytocin is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage. Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2+- dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contractions by increasing the intracellular Ca2+. Oxytocin has specific receptors in the myometrium and the receptor concentration increases greatly during pregnancy, reaching a maximum in early labor at term. The Oxytocin receptor is a typical class I G protein-coupled receptor that is primarily coupled via G(q) proteins to phospholipase C-beta. The high-affinity receptor state requires both Mg(2+) and cholesterol, which probably function as allosteric modulators. The agonist-binding region of the receptor has been characterized by mutagenesis and molecular modeling and is different from the antagonist binding site. The function and physiological regulation of the Oxytocin system is strongly steroid dependent.

Sinapultide is a synthetic peptide used to mimic human lung surfactant protein B, the most important surfactant protein for a proper functioning of the respiratory system. Protein B lowers surface tension at the air-liquid interface of the alveolar surfaces during respiration and stabilizes the alveoli against collapse at resting transpulmonary pressures. A deficiency of pulmonary surfactant in premature infants results in respiratory distress syndrome. Sinapultide compensates for the deficiency of surfactant and restores surface activity to the lungs of these infants. Sinapultide was originally developed in the Scripps Research Institute and then licensed to Windtree Therapeutics (formerly Discovery Laboratories, Inc.). Sinapultide is the active ingredient of Lucinactant, a liquid medication to treat infant respiratory distress syndrome. Lucinactant was approved by the FDA in 2012 and sold under the trademark Surfaxin, but in 2015 it was discontinued by Discovery Laboratories, Inc in favor of Aerosurf, another drug containing Sinapultide.

Peginesatide (trade name Omontys, formerly Hematide), developed by Affymax and Takeda, is an erythropoietic agent, a functional analog of erythropoietin. It was approved by the U.S. Food and Drug Administration for treatment of anemia associated with chronic kidney disease (CKD) in adult patients on dialysis. Peginesatide is a synthetic peptide, attached to polyethylene glycol ("PEGylated"). It mimics the structure of erythropoietin, the human glycoprotein which promotes red blood cell development. Peginesatide binds to and activates the human erythropoietin receptor and stimulates erythropoiesis in human red cell precursors in vitro.

Enfuvirtide is a linear 36-amino acid synthetic peptide that inhibits the fusion of HIV-1 with CD4 cells. Enfuvirtide works by disrupting the HIV-1 molecular machinery at the final stage of fusion with the target cell, preventing uninfected cells from becoming infected. Enfuvirtide interferes with the entry of HIV-1 into cells by inhibiting fusion of viral and cellular membranes. Enfuvirtide binds to the first heptad-repeat (HR1) in the gp41 subunit of the viral envelope glycoprotein and prevents the conformational changes required for the fusion of viral and cellular membranes. Enfuvirtide is indicated for the treatment of HIV-1 infection, in combination therapy with other antiretrovirals, in patients where all other treatments have failed. Common adverse drug reactions associated with enfuvirtide therapy include: injection site reactions (pain, hardening of skin, erythema, nodules, cysts, itch; experienced by nearly all patients, particularly in the first week), peripheral neuropathy, insomnia, depression, cough, dyspnoea, anorexia, arthralgia, infections (including bacterial pneumonia) and/or eosinophilia.

Desirudin (Iprivask), a recombinant hirudin, is a parenteral direct thrombin inhibitor approved to prevent venous thromboembolism in patients undergoing elective hip replacement surgery. Desirudin is a potent inhibitor of both clot-bound and freely circulating thrombin. Desirudin acts independently of anti-thrombin, forming a noncovalent irreversible complex with both the active site of thrombin as well as the fibrinogen binding site. This Desirudin–thrombin complex prevents fibrinogen cleavage and other thrombin catalyzed reactions such as the activation of clotting factors V, VIII and XIII, and thrombininduced platelet activation, resulting in a dose-dependent prolongation of activated partial thromboplastin time (aPTT). Desirudin is highly selective and has no effect on plasmin, factors IXa and Xa, tissue plasminogen activator, activated protein C, trypsin, chymotrypsin or complement activation pathways. Bleeding complications reported with the use of desirudin in patients undergoing hip-replacement surgery are similar to those reported with heparin and enoxaparin.

Nesiritide is the recombinant form of the 32 amino acid human B-type natriuretic peptide (BNP), which is normally produced by the ventricular myocardium. Human BNP binds to the particulate guanylate cyclase receptor of vascular smooth muscle and endothelial cells, leading to increased intracellular concentrations of guanosine 3'5'-cyclic monophosphate (cGMP) and smooth muscle cell relaxation. Cyclic GMP serves as a second messenger to dilate veins and arteries. Nesiritid was sold under brand name Natrecor for the intravenous treatment of patients with acutely decompensated congestive heart failure who have dyspnea at rest or with minimal activity.