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Constipation, abuse cathartic is no small matter!

Date:2020-03-02

There are many drugs to treat constipation, but most of them are not suitable for chronic constipation patients or long-term use. At present, the abuse of cathartic is more common, so it should be carefully selected in clinical practice. Common cathartics can be divided into the following categories:


1、 Irritant cathartic: it can stimulate colonic mucosa, myenteric plexus and smooth muscle, increase intestinal peristalsis and mucus secretion. Common cathartic, prepared cathartic, phenolphthalein, castor oil, etc.


Rhubarb and Senna contain anthraquinone, which is hydrolyzed by colonic bacteria to active components and only affects colon or distal ileum. When rhubarb is taken orally, it will discharge slightly soft stool 6-8 hours later; when senna leaves are taken, it will cause diarrhea 8-10 hours later. If the amount is large, it can cause abdominal pain and pelvic congestion due to too strong stimulation, so it is forbidden during menstruation and pregnancy. Anthraquinone can cause "colonic melanosis", that is, melanin deposition in colonic mucosa, usually occurs after 4-13 months of medication, and disappears after 3-6 months of discontinuation of medication, generally does not cause long-term lesions. Phenolphthalein can form soluble sodium salt when it meets with alkaline intestinal fluid in the intestine. It can stimulate the colon and has mild catharsis. It can excrete soft stool 4-8 hours after taking the medicine. Part of it is excreted by bile and reabsorbed in the intestine to form the circulation of intestine and liver, so the effect of one-time administration can be maintained for 3-4 days. After taking castor oil orally, it hydrolyzes the small intestine, releases sodium ricinoleate, stimulates the active secretion process of the small intestine, reduces the absorption of sugar, promotes the peristalsis of the intestine, and excretes loose stool 3-5 hours after taking the medicine.


Irritant cathartic can cause severe colic, long-term use can cause water electrolyte disorder and acid-base imbalance. When used regularly for many years, it can cause "diarrhea colon". Because it is difficult to identify, it is often diagnosed as stubborn constipation and more laxatives are applied, and even other improper treatments are applied.


2、 Mechanical cathartic:


It can be further divided into the following categories by increasing fecal volume or changing fecal composition to increase colonic motility:


1. Salt cathartic: for example, magnesium sulfate and sodium sulfate are not easy to be absorbed after oral administration, which increases the osmotic pressure in intestinal cavity, prevents the absorption of water, increases the volume of intestinal contents, and stimulates intestinal peristalsis due to intestinal expansion. The effect is fast, 0. 5-3 hours and 5-15 minutes after rectal administration. Can be used for acute constipation, enema is often used for fecal impaction, can not be used for a long time. Severe diarrhea can cause dehydration.


2, expansive cathartic (intestinal filling agent): this preparation contains cellulose, and after absorbing water, it forms soft gel, which makes excrement easy to discharge and can stimulate intestinal peristalsis. It can be used for a long time, especially in low fiber diet, pregnancy and withdrawal of irritant cathartic. Wheat bran, corn bran, magic Yu starch, agar, methylcellulose, plantain seed preparation, etc. all belong to this category. When taking this kind of preparation, you should pay attention to drinking more water; if there is intestinal stenosis, it can cause intestinal obstruction, so you should use it with caution.


3. Softener: as a surfactant, it can make the fat and water in the feces mix easily, and increase the intestinal secretion, such as sodium octyl butyrate (calcium). Through oral administration, it does not absorb itself, but can increase the absorption of other substances, which may be related to the hepatotoxicity of cathartic. It can only be used for a short time (1-2 weeks), so it is not suitable for chronic constipation.


4. Lubricant: such as paraffin oil. It is not digested and absorbed in the intestine, but can wrap around the fecal mass, making it easy to be discharged; at the same time, it hinders the absorption of water by the colon, so it can lubricate the intestinal cavity, soften the stool, and take effect 6-8 hours after oral administration. Long term use may hinder the absorption of fat soluble vitamins. It should not be used at the same time with surfactant to increase the absorption of mineral oil. This product still leaks from the anus, causing itching. It can only be used for a short time and is not suitable for chronic constipation.


5. Hypertonic cathartic: due to the hypertonic effect, it can increase the pressure in intestinal cavity and stimulate intestinal peristalsis. When glycerin is injected into rectum directly, it will cause defecation reflex due to the stimulation of rectal wall by hypertonic and osmotic pressure, and it also has the function of lubrication, which can cause defecation within a few minutes. Lactulose is metabolized into low molecular acid by colonic bacteria, which reduces pH value of colon and increases peristalsis of intestine.


6. Other cathartic: some cathartic used before include calomel, aloe, morning glory, Croton, sulfur, etc., which are not used now.


When dealing with constipation patients, should be familiar with the role of the above cathartic, reasonable use of diarrhea. Generally speaking, chronic constipation is mainly caused by intumescent cathartic, and irritant cathartic is only used when necessary. For acute constipation, small doses of salt cathartic, irritant cathartic, lubricant, etc. can be selected as appropriate, but not more than 1 week; if constipation cannot be corrected after more than 1 week, the medical record should be carefully searched. Those who abuse stimulant cathartic for a long time must stop using it gradually and take expansive cathartic. The author has repeatedly dealt with the long-term abuse of various laxatives. After the drug was stopped, he took bran preparation and drank more water to gradually recover the regular defecation. In this process, he can intermittently add a small amount of other laxatives as appropriate to help smooth the transition.


Many patients take all kinds of cathartic by themselves or according to the doctor's order for a long time. In fact, it takes 3-4 days for the colon to be filled again after the colon is completely emptied with cathartic at one time. Therefore, it is not appropriate to use the cathartic continuously. Generally, cathartic needs 6-8 hours to take effect after oral administration, so the more reasonable time for taking medicine should be before bed, so that it is more physiological to defecate after getting up in the next morning or after breakfast.

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