Drugs and weight loss

Generally speaking, drugs are of limited value in the treatment of obesity and should be used with great care (preferably under medical supervision) because of the possibility of dependence and abuse. The most commonly used are the `anorexigenic' drugs which work by suppressing appetite. However, their effect is only temporary and they do nothing to encourage changes in the eating habits which caused the problem in the first place. Also, an ever-increasing dosage is needed for sustained weight loss.

Side effects of these drugs include insomnia, excitability, dryness of the mouth, gastro-intestinal disturbances and addiction. Anorectics increase short-term weight loss but interestingly, follow-up indicates that patients treated with drugs lose less weight in the long term.

There are many other drugs which have received attention in the treatment of obesity. For example:

• thyroid hormone, which increases energy use. Unfortunately, both fat and protein losses occur when this drug is used. Also, the results of thyroid medication seem to be no better than those achieved with a balanced diet alone - and negative side effects involving the heart have been reported.
• growth hormone, which decreases fat stores without causing protein losses. This hormone, however, is in short supply and is not generally used in the treatment of obesity.
• human chorionic gonadotrophin (HCG), which is injected and used along with a very low calorie (500 cal/2 100 kJ) diet. It is claimed that this hormone melts away fat and reduces hunger. However, no scientific proof for these claims has been found.
• drugs which interfere with the absorption of carbohydrates and fats. This implies that one can eat as much as you like without getting fat, because all the energy is not absorbed. More research is needed on these drugs to evaluate their long-term efficacy in humans.
• bulking agents, which are intended to fill the stomach with indigestible material in the hope that the resulting feeling of fullness will make the obese person eat less. (Research indicates that this method is not very effective and that it causes flatulence.)

Perhaps the most important point to remember regarding the use of drugs in combatting overweight is that, while they may aid the slimming process, they do not solve the underlying problem and will therefore never be effective as a sole treatment for obesity.

The surgeon's knife

Surgical treatment of obesity is usually the last resort and is generally only used on the excessively obese person when all other method have failed. Surgical procedures used include small bowel bypass and/ or stapling of the stomach, biliopancreatic bypass and jaw wiring. The chances of success are small unless the patient is highly motivated and prepared to follow a very strict diet. Also, these techniques involve considerable risk and could result in the development of other health problems as side effects.

Drugs that cause increased excretion of nutrients

Diuretics are frequently taken to correct oedema (water retention) which results from a medical disorder. While they are successful in reducing the excess water level in the body, they also result in the excretion of larger amounts of potassium and magnesium. Patients being treated on a regular basis with thiazide diuretics should therefore increase their intake of foods which are high in potassium such as bananas, orange juice and potatoes.

Alcohol as a drug

Alcohol is regarded as both a drug and a food, since it supplies 29 kilojoules per gram. Because it has mood-altering effects and interferes with the absorption, metabolism and excretion of certain drugs and nutrients, it should possibly be treated with more respect than is usually the case. The reason why the effects of alcohol are felt so swiftly is that it takes a direct route into the system, traveling via the stomach to the small intestine, from where it is quickly absorbed into the blood. A small amount evaporates through the breath and perspiration, but most of it has to be processed by the liver before it isexcreted from the body via the urine.

A regular, excessive alcohol intake decreases the absorption of folic acid, thiamin, vitamin B6, vitamin B12, magnesium, zinc and other trace minerals. High alcohol consumption also tends to go hand in hand with a general decrease in food intake. Alcohol is used as a base in many over-the-counter medications and, ironically, some addicts find all-night chemists a useful secondbest after closing time at the pub!

When combined with the use of other drugs, alcohol can cause serious complications. This is because alcohol itself is a powerful drug and generally speaking, when two or more drugs are taken at the same time they often have a different (and more pronounced) effect than either produces on its own. In addition, if they both act on the same system in the body, their combined effect is often more powerful than might be expected. For example:

• In combination with barbiturates: Both alcohol and phenobarbital (a barbiturate) are depressants. When taken together, even at very low doses, these drugs may increase central nervous system depression and can be fatal.
• In combination with aspirin: Alcohol tends to irritate the stomach lining; when taken in combination with aspirin, which is also an irritant, it can cause internal bleeding.

Other medication: When alcohol is consumed with some antidepressants (ie monoamine-oxidase inhibitors) it may increase blood pressure to a dangerous level. Alcohol combined with antialcohol (Antabuse), antidiabetic and many other medications can lead to abdominal cramps, flushing and vomiting.

Drugs in disguise

Many of us know people who imbibe tea made with loquat leaves for their diabetes, or swear by certain home-brewed herbal mixtures for a multitude of ills. It would certainly be unrealistic to assume that drugs come only in the form of pills or potions created in a laboratory - the early use of the poppy for its narcotic effects is well known - but there are considerable advantages to obtaining one's medication from a pharmacist and not from the garden. These include the fact that the quantity of a compound can be controlled in a pill but not in a leaf, the question of year-round availability and, not least, the convenience.

Some foods are well-known for their adverse drug effects. Liquorice, for example, contains a compound which can cause raised blood pressure if eaten in quantity by people sensitive to this particular substance. Another interesting example (although not of local relevance) is a type of broad bean known as a lava bean' which has a drug-like effect in certain people. Some members of the population in Mediterranean countries have a metabolic defect which causes jaundice, blood in the urine and other symptoms if they eat this variety of bean.

Diet and Drug Interaction

The use of drugs or medication to maintain or restore health has increased tremendously during the past 20 years.

A 'drug' may be defined broadly as any chemical substance that is not one of the basic nutrients (proteins, carbohydrates, fats, minerals and vitamins) and which, when taken in, changes the body's structure or function. Incidentally, according to this definition, even ordinary table salt could be labelled a drug! For the purpose of this article, however, the term 'drug' will mean a non-food substance that is deliberately introduced into the body in order to produce some physiological or psychological effect. Of course drugs act in a variety of different ways, depending on their particular applications, which may be any of the following:

• relief of symptoms (such as headaches)
• prevention of illness (as in the case of vaccines used against diseases such as polio)
• control of chronic conditions such as high blood pressure
• treatment of certain diseases (for example, antibiotics which are used to treat tuberculosis).

How do drugs work?

What determines how a certain drug acts on a specific problem? Why does one have an effect on the blood vessels and another on the lungs? The answer to these questions has to do with the concept of 'receptor sites' - the idea that a drug has its effect only at specific spots within cells where the drug molecule 'fits'. (A molecule is the smallest unit of a chemical substance such as a drug.) These drug molecules do not act on the whole cell, but only at the receptor sites - and only on those cells with receptor sites that are compatible with the drug molecule. The diagram on the following is a representation of the way in which this compatibility works.

Prescription drugs - handle with care!

Whenever your doctor prescribes a medication, make sure that either he/she or your pharmacist gives you the following information:

• The name of the drug (many drugs go by different names)
• The reason you are taking it
• How the drug should be taken (before or after meals, with water, fruit juice or milk, etc)
• The dosage safety level of the drug (to prevent overdosing if you have to use the drug in an emergency)
• How often you should take the drug
• The length of time you should continue to take it
• Whether taking the drug requires any change in your diet or activities (For example, certain drugs may not be taken with alcohol and others may cause drowsiness or interfere with your coordination.)
• What side effects can you expect? (All drugs cause side effects,ranging from the trivial to the serious.)

The drug/diet link

After many years of research, health professionals have established that foods and nutrients do interact with drugs to a significant extent. In other words, medication can have an effect on a person's health and conversely, food can influence a drug's effectiveness. The risk that a drug might have an adverse nutritional effect or that drugs and food might be incompatible becomes particularly relevant when:

• the drug is an 'anti-nutrient' (in other words, it acts like a nutrient even though it is not one)
• a drug which has adverse nutritional effects is taken for a long time
• the patient is taking more than one drug at a time
• a patient's diet is either nutritionally inadequate or the patient is already malnourished
• drugs are used excessively (or there is abuse of prescription or over- the-counter drugs)
• food and/or drugs are not being properly absorbed due to disease
• the patient is not given special diet instructions when necessary
• physicians, pharmacists and dietitians are unaware of the risks involved.

The use of medication may influence nutrient intake, absorption, metabolism or excretion; in the same way, foods or their components may affect the absorption, metabolism and excretion of drugs. To paraphrase this, drugs and foods can interact by one of the following mechanisms:

• Drugs plus foods (nutrients) = changed drug effect
• Drugs plus foods (nutrients) = changed nutritional balance

How drugs affect nutrients

The ways in which drugs alter nutritional balance tend to be subtler and take longer to develop than the effects of food on medication. Drugs may have an influence on food intake due to changes in taste and appetite, they may decrease the absorption of nutrients, change their metabolism or cause them to be excreted in increased amounts (accompanied by diarrhoea and vomiting).

Drugs that affect food intake

Sensitivity to taste is one of the more delicate senses which can be affected fairly easily. Some drugs dull the tastebuds and make eating a less pleasurable experience - which, of course, may have the effect of making you eat less. Three drugs which decrease the sense of taste are clofibrate (a cholesterol-lowering agent), levodopa (an anti-Parkinson agent) and penicillamine (a chelating agent).

One or more of the four basic tastes (sweet, sour, salty and bitter) may be affected. For example, amphetamines decrease sensitivity to sweetness, while fluorouracil (a cytostatic agent) increases it. Diabetics who have to use insulin over prolonged periods find that they experience decreased sensitivity to both salty and sweet tastes. Other drugs - such as allopurinol (an anti-gout agent) - simply leave an unpleasant taste in the mouth.

Drugs that alter appetite

As the table below shows, some drugs directly stimulate the appetite, while others depress it. (Oral contraceptives, for example, tend to have the former effect.)

Drugs that decrease the absorption of nutrients

Drugs can affect the absorption of nutrients in several ways (including changes in the time the food spends in the digestive tract, in the acidity of the stomach, bile acid activity, enzyme systems, mucosal cells, or through binding to nutrients).

Firstly, the absorption of certain nutrients may be affected when the digestion of food is accelerated - a side effect of certain pills given for high blood pressure (ganglion blockers) - or when micro-organisms necessary for digestion are destroyed. In particular, drugs used to prevent indirectly the absorption of cholesterol from food into the body are often accompanied by reduced absorption of other nutrients (especially fat soluble vitamins). As another example, antacids are given to 'mop up' the excess acid in the stomach, but thiamin (vitamin B1) needs an acid medium lower down in the digestive tract to be absorbed, so antacids may impair its absorption.

Drugs that affect nutrient metabolism

Interference with nutrient metabolism can occur when a drug is similar in structure to a vitamin and therefore displaces a vitamin in a metabolic pathway. One example of this is the interaction between methotrexate (amethopterin), a cancer chemotherapeutic agent, and folic acid. Methotrexate kills cancer cells by displacing folic acid

and is therefore called a 'folic acid antagonist'. The problem is that the healthy cells are also prevented from using folic acid, which results in a type of anaemia.

The Pill and vitamin deficiency

The effect of oral contraceptives on nutritional deficiences has received wide attention in recent years. It has been shown that usage of 'the Pill' can decrease the absorption of vitamin B12, vitamin C, folic acid, vitamin B6, riboflavin, magnesium and zinc. On the plus side,however, it increases iron and calcium absorption. Although the Pill does seem to affect absorption and metabolism of many nutrients, there is little scientific evidence that women using it require increased amounts of nutrients to prevent nutritional deficiencies, provided of course that they are healthy and are following a balanced diet. In these circumstances, nutrient levels do not fall to alarming levels.

Some researchers have however established that the depression suffered by certain women who use the contraceptive pill can be due to a deficiency in vitamin B6, which can be treated by supplementation with this vitamin. A number of theories have been proposed regarding the cause of the pre-menstrual syndrome (PMS) and its link to the Pillone of these being that women who suffer from PMS also have low levels of vitamin B6. However, there is as yet not enough scientific evidence to justify fortification of the Pill with vitamin B6, or to suggest that doctors should treat the problem routinely with vitamin B6 supplementation.

How food affects drugs

In order to work properly, drugs must be present in the correct amounts at the receptor sites of the cell membranes. A number of factors can affect the way in which a drug works and, therefore, its effect on the body. Food is one of the most important of these factors. It can affect the absorption of a drug, its movement through the blood, its metabolism and its excretion.

Food and drug absorption

When drugs are taken orally, their absorption is influenced in different ways by the presence of food in the digestive tract. For example, food causes increased secretion of hydrochloric acid (HCl) in the stomach which can result in the destruction of some penicillin antibiotics that are taken by mouth. For this reason, penicillin should always be taken 1 hour before or 3 hours after meals.

Calcium in milk and dairy products tends to bind with tetracycline antibiotics to form non-absorbable compounds, with the result that the drug is lost in the stool. This means that these foods should not be eaten at the same time or within a few hours of taking the medication. However, the instruction 'Not to be taken with milk products' which sometimes appears on medicine labels can be misleading as it does not mean that you cannot consume any milk products while you are on the medication.

Iron salts (such as ferrous sulphate) can also bind with tetracycline antibiotics and result in the loss of the antibiotic. Therefore, anyone using an iron supplement as well as a tetracycline should take them at least two hours apart.

On the other hand, the absorption of some drugs can be increased when they are taken with foods. For example, foods with a high fat content increase the absorption of Griseofulvin, an antibiotic and antifungal drug. Iron supplements are also absorbed better when they are taken with vitamin C or foods rich in vitamin C, such as orange and guava juice. Interestingly, although some drugs (such as aspirin) are absorbed better on an empty stomach, they should nevertheless be taken with food - or at least milk - because of their irritating effect on the stomach lining.

Food and drug metabolism

Certain reactions inside the body can chemically change a drug (`metabolize' it) so that it is quite a different compound by the time it leaves the bloodstream. For example, some drugs combine with body proteins as they move through the bloodstream, which has the effect of preventing these drugs from entering the cells where they were intended to act. Others are broken down into smaller chemical components by the liver, the kidneys and the digestive tract. The metabolism of specific drugs can be influenced by the following in food: protein content, alcohol content, charcoal broiling, certain types of vegetables, caffeine intake, dietary fibre and the times food is eaten in relation to drug intake.

Food and the excretion of drugs

When metabolized by the body, some food alters the pH of the urine making it either more or less acidic - which in turn affects the excretion of drugs and therefore, the duration of their effects. For example, if excretion is decreased, more of the drug will be reabsorbed into the blood and its effects will be prolonged.

As an illustration, vitamin C makes the urine more acidic, thereby reducing the excretion of acidic drugs like phenobarbital and aspirin. When taking an antibiotic for a urinary tract infection, it is beneficial to acidify the urine, because this will result in decreased excretion of the antibiotic.

What drugs should you take when?

In order to minimize the adverse effects of foods on drug absorption, metabolism and excretion, the timing of drug administration in relation to food intake is very important. This is why it is essential to adhere to any such instructions which may accompany a prescribed drug. For example:

• If rapid absorption of the drug is desired, the doctor/pharmacist may specify on the prescription that the drug should be taken before meals.
• Drugs that irritate the stomach (such as indomethacin, phenobarbitone) should be taken when the stomach is 'cushioned' with food. In this case, the prescription should specify that the drug is to be taken after (or in the middle of) a meal.
• Fat-soluble drugs should not be taken with a fatty meal, since the medication will be absorbed with the fat content in the food; because fat is digested slowly, the drug may not be absorbed into the bloodstream as rapidly as it should be.
• Acetylsalicylic acid, Bisacodyl, Erythromycin and tetracyclines should not be taken with milk (see above).
• Ampicillin, Cloxacillin and Erythromycin-based drugs, as well as stearate and Penicillin G should not be taken with fruit juices or carbonated beverages.