Hydroquinone, aka benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2. Its chemical structure features two hydroxyl groups bonded to a benzene ring in a para position. It is a white granular solid. Substituted derivatives of this parent compound are also referred to as hydroquinones. The name "hydroquinone" was coined by Friedrich Wöhler in 1843. In human medicine, hydroquinone is used as a topical application in skin whitening to reduce the color of skin. It does not have the same predisposition to cause dermatitis as metol does. In 2006, the United States Food and Drug Administration revoked its previous approval of hydroquinone and proposed a ban on all over-the-counter preparations. The FDA stated that hydroquinone cannot be ruled out as a potential carcinogen. This conclusion was reached based on the extent of absorption in humans and the incidence of neoplasms in rats in several studies where adult rats were found to have increased rates of tumours, including thyroid follicular cell hyperplasias, anisokaryosis (variation in nuclei sizes), mononuclear cell leukemia, hepatocellular adenomas and renal tubule cell adenomas. One of the components in TRI-LUMA Cream, hydroquinone, is a depigmenting agent, and may interrupt one or more steps in the tyrosine-tyrosinase pathway of melanin synthesis. However, the mechanism of action of the active ingredients in TRI-LUMA Cream in the treatment of melasma is unknown.

Succimer is an analogue of dimercaprol, and has replaced dimercaprol as one of the main antidotes used in the management of poisoning by lead and other heavy metals. The advantages of succimer are that it is effective by oral administration because it is soluble in water, it is well-tolerated, has relatively low toxicity and can be given at the same time as iron supplements to treat iron deficiency anaemia. It does not cause significant increase in urinary excretion of essential minerals unlike the other widelyused lead chelating agent, sodium calcium EDTA.

Pindolol was developed at Sandoz at 1960s. Pindolol is a nonselective beta-adrenergic antagonist (beta-blocker) which possesses intrinsic sympathomimetic activity (partial agonist activity) in therapeutic dosage ranges but does not possess quinidine-like membrane stabilizing activity. The partial beta-adrenergic agonistic activity of pindolol in the heart appears to be completely restricted to the sinoatrial pacemaker. In standard pharmacologic tests in man and animals, Pindolol attenuates increases in heart rate, systolic blood pressure, and cardiac output resulting from exercise and isoproterenol administration, thus confirming its beta-blocking properties. In addition to beta-adrenergic activity pindolol demonstrates mixed agonist-antagonist activity at central 5-HT receptors. Although in accordance with the hypothesis that pindolol increases the antidepressant effects of selective serotonin reuptake inhibitors by antagonism of 5-HT at inhibitory 5-HT1A autoreceptors, pindolol possesses partial agonist activity at 5-HT1A receptors. Pindolol tablets are indicated in the management of hypertension.

Econazole (commonly used as the nitrate salt) is an antifungal medication of the imidazole class. It is a broad spectrum antimycotic with some action against Gram positive bacteria. It is used topically in dermatomycoses also orally and parenterally. Sold under the brand name Ecoza among others, it is indicated for the treatment of interdigital tinea pedis caused by Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosum in patients 12 years of age and older. Econazole interacts with 14-α demethylase, a cytochrome P-450 enzyme necessary to convert lanosterol to ergosterol. As ergosterol is an essential component of the fungal cell membrane, inhibition of its synthesis results in increased cellular permeability causing leakage of cellular contents. Econazole may also inhibit endogenous respiration, interact with membrane phospholipids, inhibit the transformation of yeasts to mycelial forms, inhibit purine uptake, and impair triglyceride and/or phospholipid biosynthesis.

Nadolol is a nonselective beta-adrenergic receptor antagonist with a long half-life, and is structurally similar to propranolol. Clinical pharmacology studies have demonstrated beta-blocking activity by showing (1) reduction in heart rate and cardiac output at rest and on exercise, (2) reduction of systolic and diastolic blood pressure at rest and on exercise, (3) inhibition of isoproterenol-induced tachycardia, and (4) reduction of reflex orthostatic tachycardia. Nadolol has no intrinsic sympathomimetic activity and, unlike some other beta-adrenergic blocking agents, nadolol has little direct myocardial depressant activity and does not have an anesthetic-like membrane-stabilizing action. Like other beta-adrenergic antagonists, nadolol competes with adrenergic neurotransmitters such as catecholamines for binding at sympathetic receptor sites. Like propranolol and timolol, nadolol binds at beta(1)-adrenergic receptors in the heart and vascular smooth muscle, inhibiting the effects of the catecholamines epinephrine and norepinephrine and decreasing heart rate, cardiac output, and systolic and diastolic blood pressure. It also blocks beta-2 adrenergic receptors located in bronchiole smooth muscle, causing vasoconstriction. By binding beta-2 receptors in the juxtaglomerular apparatus, nadolol inhibits the production of renin, thereby inhibiting angiotensin II and aldosterone production. Nadolol therefore inhibits the vasoconstriction and water retention due to angiotensin II and aldosterone, respectively. Nadolol is used in cardiovascular disease to treat arrhythmias, angina pectoris, and hypertension.

Trimipramine is a tricyclic antidepressant similar to imipramine, but with more antihistaminic and sedative properties. It was sold under brand name surmontil for the relief of symptoms of depression. Endogenous depression is more likely to be alleviated than other depressive states. In studies with neurotic outpatients, the drug appeared to be equivalent to amitriptyline in the less-depressed patients but somewhat less effective than amitriptyline in the more severely depressed patients. In hospitalized depressed patients, trimipramine and imipramine were equally effective in relieving depression. Trimipramine has been reported to differ from other typical tricyclic antidepressant drugs in several aspects, for instance it does not inhibit neuronal transmitter uptake and does not cause down-regulation of beta-adrenoceptors. Moreover, it may possess antipsychotic activity in schizophrenic patients. In addition, was found that it did not antagonize the inhibitory effect of noradrenaline and 5-hydroxytryptamine on the release of transmitter, mediated by presynaptic auto receptors. In radioligand binding studies, trimipramine showed fairly high affinities for some dopamine (DA), noradrenaline and 5-hydroxytryptamine (5-HT) receptor subtypes (5-HT2 receptors = alpha 1A/B-adrenoceptors greater than or equal to D2 receptors), intermediate affinities for D1 receptors, alpha 2B-adrenoceptors and 5-HT1C receptors but only low affinities for alpha 2A-adrenoceptors, 5-HT1A, 5-HT1D and 5-HT3 receptors. It may thus be classified as an atypical neuroleptic drug.

Verapamil is a FDA approved drug used to treat high blood pressure and to control chest pain. Verapamil is an L-type calcium channel blocker that also has antiarrythmic activity. The R-enantiomer is more effective at reducing blood pressure compared to the S-enantiomer. However, the S-enantiomer is 20 times more potent than the R-enantiomer at prolonging the PR interval in treating arrhythmias. Verapamil inhibits voltage-dependent calcium channels. Specifically, its effect on L-type calcium channels in the heart causes a reduction in ionotropy and chronotropy, thuis reducing heart rate and blood pressure. Verapamil's mechanism of effect in cluster headache is thought to be linked to its calcium-channel blocker effect, but which channel subtypes are involved is presently not known.

Cimetidine is a histamine H2-receptor antagonist. It reduces basal and nocturnal gastric acid secretion and a reduction in gastric volume, acidity, and amount of gastric acid released in response to stimuli including food, caffeine, insulin, betazole, or pentagastrin. It is used to treat gastrointestinal disorders such as gastric or duodenal ulcer, gastroesophageal reflux disease, and pathological hypersecretory conditions. Cimetidine inhibits many of the isoenzymes of the hepatic CYP450 enzyme system. Other actions of Cimetidine include an increase in gastric bacterial flora such as nitrate-reducing organisms. Cimetidine binds to an H2-receptor located on the basolateral membrane of the gastric parietal cell, blocking histamine effects. This competitive inhibition results in reduced gastric acid secretion and a reduction in gastric volume and acidity.

Prazosin (trade names Minipress, Vasoflex, Lentopres, and Hypovase) is a selective α-1-adrenergic receptor antagonist used to treat hypertension. Prazosin acts by inhibiting the postsynaptic alpha-1-adrenoceptors on vascular smooth muscle. This inhibits the vasoconstrictor effect of circulating and locally released catecholamines (epinephrine and norepinephrine), resulting in peripheral vasodilation. Prazosin is orally active and has a minimal effect on cardiac function due to its alpha-1 receptor selectivity. However, when prazosin is started, heart rate and contractility go up in order to maintain the pre-treatment blood pressures because the body has reached homeostasis at its abnormally high blood pressure. The blood pressure lowering effect becomes apparent when prazosin is taken for longer periods of time. The heart rate and contractility go back down over time and blood pressure decreases. The antihypertensive characteristics of prazosin make it a second-line choice for the treatment of high blood pressure. Prazosin is also useful in treating urinary hesitancy associated with prostatic hyperplasia, blocking alpha-1 receptors, which control constriction of both the prostate and urethra. Although not a first line choice for either hypertension or prostatic hyperplasia, it is a choice for patients who present with both problems concomitantly. Common (4–10% frequency) side effects of prazosin include dizziness, headache, drowsiness, lack of energy, weakness, palpitations, and nausea. Less frequent (1–4%) side effects include vomiting, diarrhea, constipation, edema, orthostatic hypotension, dyspnea, syncope, vertigo, depression, nervousness, and rash.