Luminal

LUMINAL, Luminal, phenylethylbarbituric acid, C₁₂H₁₂N₂O₃, is a white crystalline powder, odorless, with a bitter taste, melting at 170–172°, poorly soluble in cold water (1:1000), better in hot water, and well soluble in organic solvents, fats, and oils. Solubility in water increases upon the addition of alkalis (e.g., sodium bicarbonate) due to the formation of a readily soluble sodium salt. Luminal is absorbed slowly and is excreted almost completely in an unchanged form slowly by the kidneys. Luminal accumulates, which is why a break of 1–2 days should be taken after several days of administration. Differing from Veronal by the substitution of one of the ethyl groups with a phenyl group, Luminal, due to the presence of the latter, possesses a significantly more pronounced depressant effect on the central nervous system. Its hypnotic effect therefore occurs at lower doses (0.1–0.2), and due to slow absorption (it is recommended to wash down Luminal with a sufficient amount of warm or hot water), sleep occurs only after 1–1.5 hours. Sleep is sufficiently deep and lasts 6–8 hours; after waking, weakness, dizziness, and headache are often observed. Because of the complications just mentioned, it is not recommended to use Luminal for ordinary insomnia, replacing it with other derivatives of barbituric acid, e.g., Veronal; Luminal is prescribed only in those cases where insomnia is associated with a state of anxiety and agitation. In connection with this, Luminal is more often prescribed as a hypnotic in psychiatric practice, all the more so because the phenomena complicating the hypnotic effect of Luminal and impairing performance have less significance here than in mentally healthy subjects. In smaller doses (0.05), Luminal acts as a sedative and is used for various neuroses. A good therapeutic effect has been obtained when prescribing Luminal for migraine, chorea, paralysis agitans, eclampsia, and states of agitation in neuropathic children. Luminal has particular significance in the treatment of epilepsy (Hauptmann, 1912), as it prevents persistent seizures that do not respond to other therapeutic agents. In such cases, it is prescribed twice a day at 0.05 with a gradual increase of the single dose to 0.2 and its subsequent reduction. According to clinical observations, Luminal leads in ordinary therapeutic doses to a clear lowering of blood pressure (in experiments on animals, this effect at average doses of Luminal is expressed unclearly), and it is therefore sometimes prescribed in the treatment of hypertension. Habituation to Luminal is almost not observed. The side effect of Luminal, besides the above-mentioned symptoms from the central nervous system, is expressed in the frequent occurrence of rashes (scarlatiniform erythema, urticaria). Luminal poisoning is characterized by a state of stupor, phenomena of ataxia, and in more severe cases, visual disturbances, miosis with the absence of pupillary reaction to light, coma, and Cheyne-Stokes respiration. Toxic doses begin from 0.5–0.75, and one should take into account individual variations in sensitivity to the drug; in connection with this, it is recommended, when starting treatment with Luminal, to prescribe it first in smaller doses (0.05–0.1). Treatment of poisoning has nothing specific and boils down mainly to measures stimulating the central nervous system (caffeine, camphor) and to combating the lowering of blood pressure (infusion of physiological saline with adrenaline). The maximum single dose of Luminal is 0.4; the maximum daily dose is 0.8; for children of school age, the maximum single dose is 0.1. Luminal-sodium, as a readily soluble preparation, is prescribed subcutaneously (1 cm³ of a 20% solution of Luminal-sodium) or in an enema. Solutions must be prepared ex tempore, as they give a precipitate upon storage. When administered per os, Luminal-sodium has no advantages.