Dyclonine Hydrochloride is an oral local anesthetic. Dyclonine reversibly binds to activated sodium channels on the neuronal membrane, thereby decreasing the neuronal membrane's permeability to sodium ions, leading to an increased threshold for excitation. This reversibly stabilizes the membrane and inhibits depolarization, leading to the failure of a propagated action potential and subsequent conduction blockade. This results in a transient and reversible loss of sensation in a localized area of the body.

Droperidol is a D1DR and D2DR inhibitor, an antidopaminergic drug used as an antiemetic and antipsychotic. Droperidol is also often used for neuroleptanalgesic anesthesia and sedation in intensive-care treatment. It has also been used as an antipsychotic in doses ranging from 5 to 10 mg given as an intramuscular injection, generally in cases of severe agitation in a psychotic patient who is refusing oral medication. Its use in intramuscular sedation has been replaced by intramuscular preparations of haloperidol, midazolam, clonazepam and olanzapine.

Doxycycline Hyclate is the hyclate salt form of a synthetic, broad-spectrum tetracycline antibiotic exhibiting antimicrobial activity. It is an antimicrobial tetracycline that acts as an inhibitor of a wide range of matrix metalloproteinases (MMPs) of MMP-1 and MMP-8. Doxycycline hyclate binds reversibly to the 30S ribosomal subunit, possibly to the 50S ribosomal subunit as well, thereby blocking the binding of aminoacyl-tRNA to the mRNA-ribosome complex. This leads to an inhibition of protein synthesis.

Doxazosin is an α-1 adrenergic receptor blocker that inhibits the binding of norepinephrine, which is released from sympathetic nerve terminals, to the α-1 receptors on the membrane of vascular smooth muscle cells. Blockages of the alpha-1 adrenergic action on the vascular smooth muscles lead to a decrease in vascular resistance and antihypertensive activity. This agent also shows high affinity to alpha-1c adrenoceptor, the predominant functional type in the prostate, which may partially attribute to its effect in treatment of benign prostatic hyperplasia.

Dorzolamide is a carbonic anhydrase inhibitor. It is an anti-glaucoma agent, and acts by decreasing the production of aqueous humour. It is administered as a topical ophthalmic in the form of a 2% solution.

Dolasetron is a serotonin 5-HT3 receptor antagonist used to treat nausea and vomiting following chemotherapy. Its main effect is to reduce the activity of the vagus nerve, which is a nerve that activates the vomiting center in the medulla oblongata. It does not have much antiemetic effect when symptoms are due to motion sickness. This drug does not have any effect on dopamine receptors or muscarinic receptors.

Dobutamine is a sympathomimetic drug used in the treatment of heart failure and cardiogenic shock. Its primary mechanism is direct stimulation of β1 receptors of the sympathetic nervous system.

Disopyramide is an antiarrhythmic medication used in the treatment of Ventricular Tachycardia. It is a sodium channel blocker and therefore classified as a Class 1a anti-arrhythmic agent. Disopyramide has a negative inotropic effect on the ventricular myocardium, significantly decreasing the contractility.

Diphenylpyraline is a first-generation antihistamine with anticholinergic effects of the diphenylpiperidine class.

Diphenhydramine is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties that is mainly used to treat allergies. It is also used in the management of drug-induced parkinsonism and other extrapyramidal symptoms.

Dimenhydrinate is an over-the-counter antiemetic used for the treatment of the symptoms of motion sickness.

Diltiazem is a nondihydropyridines (non-DHP) calcium channel blocker used in the treatment of hypertension, angina pectoris, and some types of arrhythmia. It relaxes the smooth muscles in the walls of arteries, which opens (dilates) the arteries, allows blood to flow more easily, and lowers blood pressure.

Diloxanide is a luminal amebicide used in the treatment of amebiasis. It is considered the luminal agent of choice for mild intestinal amebiasis or asymptomatic cyst carriers. It can also be added to metronidazole (active drug in luminal and extraintestinal amebiasis) in acute amebic dysentery as well as hepatic abscess (In hepatic abscess it is for the control of cysts in the lumen which may cause relapse).

Dihydrotachysterol is a synthetic vitamin D analog activated in the liver that does not require renal hydroxylation like vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). DHT has a rapid onset of action (2 hours), a shorter half-life, and a greater effect on mineralization of bone salts than does vitamin D.

Dienestrol is a synthetic, non-steroidal estrogen structurally related to stilbestrol. It is used, usually as the cream, in the treatment of menopausal and postmenopausal symptoms. It is an estrogen receptor agonist. Estrogens work partly by increasing a normal clear discharge from the vagina and making the vulva and urethra healthy. Using or applying an estrogen relieves or lessens: dryness and soreness in the vagina, itching, redness, or soreness of the vulva. Conditions that are treated with vaginal estrogens include a genital skin condition (vulvar atrophy), inflammation of the vagina (atrophic vaginitis), and inflammation of the urethra (atrophic urethritis).

Dicyclomine is an anticholinergic that blocks muscarinic receptors. Dicyclomine is used to treat intestinal hypermotility and the symptoms of irritable bowel syndrome (also known as spastic colon). It relieves muscle spasms and cramping in the gastrointestinal tract by blocking the activity of acetylcholine on cholinergic (or muscarinic) receptors on the surface of muscle cells. It is a smooth muscle relaxant.

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) taken or applied to reduce inflammation and as an analgesic reducing pain in certain conditions. It is supplied as or contained in medications under a variety of trade names. As a nonsteroidal anti-inflammatory drug (NSAID), Diclofenac binds and chelates both isoforms of cyclooxygenase (COX-1 and-2), thereby blocking the conversion of arachidonic acid to pro-inflammatory-proprostaglandins. This agent also may inhibit COX-2-mediated tumor angiogenesis. When inhibiting COX-2, Diclofenac may be effective in relieving pain and inflammation; when inhibiting COX-1, it may produce unacceptable gastrointestinal side effects. This agent may be more active against COX-2 than several other carboxylic acid-containing NSAIDs.

Dibucaine (USAN) is an amide local anesthetic. Dibucaine reversibly binds to and inactivates sodium channels in the neuronal cell membrane. Inhibition of sodium channels prevents the depolarization of nerve cell membranes and inhibits subsequent propagation of impulses along the course of the nerve, thereby limiting the excitation of nerve endings. This results in loss of sensation. Among the most potent and toxic of the long-acting local anesthetics, current use of dibucaine is generally restricted to spinal and topical anesthesia. It is sold under the brand names Cincain, Nupercainal, Nupercaine and Sovcaine. (Source: https://en.wikipedia.org/wiki/Cinchocaine).

Diatrizoic acid (or its anionic form, diatrizoate), also known as amidotrizoic acid, or 3,5-diacetamido-2,4,6-triiodobenzoic acid, is a radiocontrast agent containing iodine. Trade names include Hypaque, Gastrografin and Urografin, the latter being a combination of the sodium and meglumine salts. Diatrizoate is considered a high-osmolality contrast agent.

Dextrothyroxine (trade name Choloxin) saw research as an cholesterol-lowering drug but was pulled due to cardiac side-effects. It also increases hepatic lipase which in turn improves utilization of triglycerides, improving apolipoprotein E cholesterol particles. (Source: https://en.wikipedia.org/wiki/Dextrothyroxine).

Dexmedetomidine, sold under the trade names Precedex and Dexdor, among others, is an anxiolytic, sedative, and analgesic medication. Similar to clonidine, it is an agonist of α2-adrenergic receptors in certain parts of the brain. Dexmedetomidine is notable for its ability to provide sedation without risk of respiratory depression (unlike other commonly used sedatives such as propofol, fentanyl, and midazolam) and can provide cooperative or semi-arousable sedation. Dexmedetomidine hydrochloride is also used in veterinary medicine for dogs and cats. The drug was developed by Orion Pharma. (Source: https://en.wikipedia.org/wiki/Dexmedetomidine).

Desvenlafaxine (brand name: Pristiq, Desfax), also known as O-desmethylvenlafaxine, is an antidepressant of the serotonin-norepinephrine reuptake inhibitor (SNRI) class developed and marketed by Wyeth (now part of Pfizer). Desvenlafaxine is a synthetic form of the major active metabolite of venlafaxine (sold under the brand names Effexor and Efexor). It is being targeted as the first non-hormonal based treatment for menopause. Desvenlafaxine is a synthetic phenethylamine bicyclic derivative with antidepressant activity. Desvenlafaxine is a selective reuptake inhibitor of serotonin and norepinephrine due to its high binding affinities to the pre-synaptic serotonin and norepinephrine transporters. By blocking both transporters, this agent prolongs neurotransmitter activities of both serotonin and norepinephrine, thereby alleviating depressive state. (Source: https://en.wikipedia.org/wiki/Desvenlafaxine).

Demeclocycline (INN, BAN) (brand names Declomycin, Declostatin, Ledermycin, Bioterciclin, Deganol, Deteclo), also known as demeclocycline hydrochloride (USAN) (brand names Detravis, Meciclin, Mexocine, Clortetrin), is a semisynthetic tetracycline antibiotic which was derived from a strain of Streptomyces aureofaciens. Demeclocycline binds to bacterial 30S ribosomal subunit and prevents binding of aminoacyl-tRNA to the mRNA-ribosome complex, thereby inhibiting protein synthesis. Demeclocycline also inhibits the effect of vasopressin on the renal tubules, thereby causing diuresis. (Source: https://en.wikipedia.org/wiki/Demeclocycline).

Deferoxamine is a bacterial siderophore produced by the Actinobacteria Streptomyces pilosus. It has medical applications as a chelating agent used to remove excess iron from the body. The mesylate salt of DFO-B is commercially available. It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. Deferoxamine acts by binding free iron in the bloodstream and enhancing its elimination in the urine.

Decamethonium (Syncurine) is a depolarizing muscle relaxant or neuromuscular blocking agent, and is used in anesthesia to induce paralysis. Decamethonium, which has a short action time, is similar to acetylcholine and acts as a partial agonist of the nicotinic acetylcholine receptor. In the motor endplate, it causes depolarization, preventing further effects to the normal release of acetylcholine from the presynaptic terminal, and therefore preventing the neural stimulus from affecting the muscle.

Debrisoquine is a derivative of guanidine. It is an antihypertensive drug similar to guanethidine. Debrisoquine is frequently used for phenotyping the CYP2D6 enzyme, a drug metabolizing enzyme.

Dantrolene sodium is a postsynaptic muscle relaxant that lessens excitation-contraction coupling in muscle cells. It achieves this by inhibiting Ca2+ ions release from sarcoplasmic reticulum stores by antagonizing ryanodine receptors. It is the primary drug used for the treatment and prevention of malignant hyperthermia, a rare, life-threatening disorder triggered by general anesthesia. It is also used in the management of neuroleptic malignant syndrome, muscle spasticity (e.g. after strokes, in paraplegia, cerebral palsy, or patients with multiple sclerosis), and 2,4-dinitrophenol poisoning.

Dalfampridine is a potassium channel blocker used to help multiple sclerosis patients walk. This is the first drug that was specifically approved to help with mobility in these patients. It has been approved by the FDA for use as a treatment for multiple sclerosis.

Cyclopentolate is a parasympatholytic anticholinergic used solely to obtain mydriasis or cycloplegia. It is commonly used during pediatric eye examinations to dilate the eye (mydriatic), prevent accommodation of the eye to different distances (cycloplegic), and block specific receptors called muscarinic receptors (muscarinic antagonist). Cyclopentolate is also administered as an atropine substitute to reverse muscarinic and central nervous system effects of indirect cholinomimetic (anti-AChase) administration.

Cyclandelate is a direct-acting smooth muscle relaxant vasodilator used in the treatment of claudication, arteriosclerosis and Raynaud's disease. It is also used to treat nighttime leg cramps, and has been investigated for its effect against migraine. It is orally administered.