|
PEOPLE AND DRUGS. ALL KINDS OF INTERESTING FACTS |
Ever wonder what happens when you swallow a pill? Actually, it breaks up in the gastrointestinal tract, is absorbed by tiny blood vessels, and is sent to every body part reachable by the blood. It is sent to body organs (liver, kidney, brain, heart, etc.), muscle tissue, fat tissue, bone, and blood proteins including albumins. Some drugs are more soluble in fat tissue than in water, and people with high body fat (up to 50% in some cases) will store fat-soluble drugs in their body fat. Drugs stored in fat will persist longer in the body; water-soluble drugs are more quickly eliminated.
The HALF-LIFE of a drug (t-1/2) is the time it takes for one-half of the dose to be eliminated. Valium, a fat-soluble drug, has a longer half-life in obese people than in thin prople.
The BLOOD-BRAIN BARRIER (BBB), (the fat-covered membranes that surround capillaries in the brain), can stop many water-soluble drugs from entering the brain. Fat-soluble drugs can better penetrate the BBB. Marijuana, tranquilizers and narcotics can easily pass the BBB.
The PLACENTAL BARRIER isn't much of a barrier at all, for almost all of the drugs that enter a pregnant mother's blood will cross over into the unborn's circulation. If you are pregnant and ingest alcohol, so does your unborn. If you smoke, so does your fetus. Drugs that pass the placental barrier and cause birth defects in the unborn are termed TERATOGENS. Read my book "Drugs and the Human Body", Sixth Edition, for extremely important information about teratogens, including some acne medicines.
The human liver, rich in enzymes, is the primary site of METABOLISM OF DRUGS (biotransformation). Just about every drug or chemical you can think of can be broken down chemically by the liver - usually by oxidation - changed into a water-soluble product, and then exreted in the urine. Breakdown products are termed METABOLITES. The urine test for marijuana (MJ) is a test for MJ metabolites, not for MJ itself.
All of us (except idential twins) have a different, unique genetic makeup. This means we can produce different kinds and amounts of liver enzymes, and this explains how people can react differently to the same drug. One person can be a fast metabolizer, another a slow. The difference between them can be as high as a factor of 20. Other factors that can influence how we react to drugs are age, sex, weight, physical condition, mental attitude, and circadian rhythms.
TOLERANCE to some drugs, that is, the need to take ever larger doses to achieve the same effect, can develop after long use of medium to high doses. Tolerance can be explained by the response of the liver to make ever larger amounts of the metabolizing enzyme as the drug is taken over a long period. This is especially true if the dose of the drug is increased. When the drug is withdrawn, tolerance typically disappears. Humans can become quite tolerant to alcohol, opiate narcotics, amphetamines, barbiturates and minor tranquilizers. Tolerance explains how some people manage to drive on our highways with a blood alcohol concentration of 0.3 to 0.4 percent! And how an addict can ingest 1000 mg of morphine in one day and not succumb!
APHRODISIACS are drugs or chemicals that arouse the sexual instinct. Alcohol is not really an aphrodisiac, but a CNS depressant and thus a disinhibitor. Actually, few if any substances are true aphrodisiacs. The much-touted "Spanish fly" (dried insects of the species Cantharis) is actually a dangerous blisterting agent that causes and pain and genital swelling.
For much, much more on drug interactions, excretion of drugs, drugs in our diet, women's health, circadian rhythms and drugs and sex, see Chapter Four in my book, "Drugs and the Human Body, Seventh Edition, Prentice Hall publishers. ISBN 0-13-177321-6. | |