Marihuana
Marihuana is unique among the controlled substances. It has some analgesic proper ties, albeit mild, and was, at one time, classified as a narcotic for pharmacologic and political reasons. It also has some sedative properties, also mild. It is most famous for its mild hallucinogenic effects and here is where it seems to be best classified. Marihuana leaves are shown in Figure 13.8. Unlike the other hallucinogens discussed in this section, marihuana has been purported to have beneficial medical effects. These include antiemetic (relieves nausea and upset stomach) effects for symptoms caused by anticancer drugs. It has also been linked to the reduction of eye pressure caused by glaucoma. It is important to note that as of now, the FDA does not recognize any of these or other medical effects of marihuana and therefore, the Federal Government maintains the position that marihuana has no accepted medical use. The marihuana plant grows worldwide. It belongs to the genus Cannabis. In the 1960s, there was controversy over how many species there are in this genus. Some botanists felt that there was evidence for 4 species; sativa, indicus, gigantis, and ruderalis. Others believed that there is only one species, sativa, and the others are regional variants of this plant. When the Federal Government first controlled marihuana, the legal literature and statutes referred to it as Cannabis sativa. In the 1960s and 1970s there were many legal problems with prosecutions of marihuana cases in state and federal courts because it is virtually impossible to determine which species is present if one is presented with dried, chopped up leaves. Forensic scientists were being challenged to prove that what was seized met the requirements of the law, namely that it was C. sativa and not a different species. To respond to these challenges, Congress and state legislatures took note that all marihuana, no matter what species it might be, contains the active ingredients that give the plant its hallucinogenic properties; the cannabinoid alkaloids, chiefly ∆9-tetrahydrocannabinol (THC). They changed the legal description of marihuana to include all members of the genus Cannabis, and that ended the legal skirmishing. Marihuana is currently controlled as a Federal Schedule I substance. For many years there has been an active legalization lobby in the United States and elsewhere. In the United States, the most enduring group is called the National Organization for the Reform of Marihuana Laws (NORML). They advocate and lobby for decriminalization and legalization of marihuana. Marihuana has been used for thousands of years. The bark of the plant is especially useful for making a type of rope called hemp and marihuana is sometimes called the hemp plant. In some countries (e.g., Japan), marihuana is still grown for its hemp. In the United States colonial times, George Washington was known to cultivate marihuana for hemp! Some “counterculture” shops in the United States and elsewhere sell clothing that is woven out of hemp. The THC content of marihuana varies regionally. In some low-grade plants it is less than 1%. With careful breeding and cultivation and removal of male plants a form of female, seedless marihuana called sinsemilla, can be grown with THC content as high as 10%. There is also a Federal Government that supported experimental farm in Mississippi, where marihuana with THC content over 30% has been cultivated. The THC in marihuana is concentrated in the resin, which is most abundant in the flowering tops and leaves of the plant. The stalks, seeds, and roots contain almost no THC and are generally removed. The leaves and flowers are dried and then smoked. In many jurisdictions, marihuana stems and stalks are not controlled and seeds are only controlled if they are viable (they can be germinated). Concentrated forms of marihuana are prepared in various ways and known by different names all over the world. In the United States, the plant material can be boiled in methyl alcohol, filtered, and then evaporated down to a thick, gooey liquid known as hashish (hash) oil. High quality hash oil may contain more than 50% THC. Another preparation, hashish (hash) is prepared by collecting the resin from the live plants with leather straps and cloths. It consists of resin and hairs from the plant. It is a solid and is often sold in bricks. Hash oil and hash are generally smoked in small pipes that are designed for this purpose. The dish in the center of Figure 1 shows some pieces of hashish. Marihuana has some interesting effects on some people in that it appears that smoking and enjoying the drug involves a learning process. This consists of learning just how long to keep the smoke in the lungs before exhaling and learning how to recognize and cultivate the mild hallucinogenic effects. These behavioral characteristics may lead to a type of “reverse tolerance” whereby the effects seem to be stronger as one gets more experienced in smoking. Some of this reverse tolerance may be due to a very long half-life for THC, which has been found in some tissues for months after the last ingestion. Marihuana also seems to have an appetite stimulating effect on many people, especially inexperienced users who report that they get the “munchies” and want to eat great quantities of food after smoking marihuana.
FIGURE 1 Hashish (in dish in center), marihuana leaves and some of the different types of pipes that are used to smoke it. Hash is made by extracting marihuana with a solvent such as methanol and then allowing it to evaporate. The residue is generally formed into bricks and allowed to dry.
