Why do some medicines need to be taken before meals

Drugs are no strangers to us. When we are sick, doctors will prescribe us various medicines. Some are Western medicine, and some are Chinese medicine. When using medicines, we usually read the instructions carefully. The instructions will provide detailed information on the chemical composition of the drug, or its usage and dosage. So why do some medicines need to be taken before meals? Let’s take a look below.

To reduce irritation to the digestive system, most medications should be taken after meals. However, some medicines must be taken on an empty stomach before meals to reduce or delay the impact of food on drug absorption and pharmacological effects, improve the safety and stability of drugs, and exert the best efficacy of drugs. The main medicines that should be taken on an empty stomach before meals include:

Some antibacterial drugs: such as ampicillin, cephalexin, cefradine, cefaclor, erythromycin, roxithromycin, rifampicin, isoniazid, etc. These drugs are easily absorbed by cellulose in food, affecting drug absorption. It has been reported that the absorption concentration of cefaclor taken after meals is only 50%-70% of that taken on an empty stomach.

Oral nutritional medicines: such as ginseng preparations, deer antler essence, royal jelly, Liuwei Dihuang Pills and other tonic medicines with little gastrointestinal irritation. These drugs are taken on an empty stomach and are not affected by food when they reach the small intestine. They are absorbed quickly and completely and have significant therapeutic effects.

Gastrokinetic drugs: such as domperidone (Motilium), metoclopramide (Metoclopramide), and cisapride (Pribos). These drugs should be taken 30 minutes before meals. When the patient eats a meal, the blood concentration of the drug in the body reaches its peak, and the gastrointestinal tract begins to move normally under the pharmacological action, exerting its therapeutic effect.

Gastrointestinal antispasmodics: such as atropine, belladonna tablets, etc. Taking the drug on an empty stomach allows the drug to take effect quickly, relieve gastrointestinal spasm, and maintain effective blood drug concentrations.

Gastric wall protective drugs: such as aluminum hydroxide (Weisuoping), magnesium trisilicate, colloidal pectin bismuth, etc. Taking the medicine before meals allows it to evenly form a protective film on the stomach wall, which can not only neutralize stomach acid but also protect the ulcerated surface or inflamed mucosa of the stomach wall.

Astringents: such as tannic acid protein, smectite, bismuth subcarbonate, etc. Taking the drug on an empty stomach allows it to pass through the stomach more quickly into the small intestine, where it reacts with alkaline intestinal fluid to decompose into tannic acid, aluminum oxide, and alkaline bismuth carbonate, which have an antidiarrheal effect.

Adsorbents: such as activated carbon. When taken on an empty stomach, there is less food in the stomach, making it easier to absorb harmful substances and gases in the gastrointestinal tract.

Choleretics: such as small doses of magnesium sulfate, bile salts, etc. Taking the drug on an empty stomach prevents the concentration from being overly diluted when passing through the stomach, allowing it to smoothly reach the bile duct outlet in the duodenum to exert its choleretic effect.

Bitter medicines: such as Chinese herbal preparations such as gentian and rhubarb. It is best to take it 10 minutes before meals. The bitter taste of the medicine can stimulate the taste buds and other peripheral nerves, promote the secretion of saliva and gastric juice, and increase appetite.

Digestive aids: such as Lactase, Multienzyme tablets, etc. It needs to be taken shortly before meals so that the medicine can be fully mixed with food, which is beneficial to the decomposition and absorption of sugars, fats and proteins in food.

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