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Dulcolax - the Effective and Gentle Laxative

Last updated on June 2nd, 2023

For many of us, the use of an effective, yet gentle laxative is what is required to overcome constipation. Dulcolax tablets for example have a special comfort so that they pass easily through the stomach and small intestine without being dissolved in relevant amounts by the gastric fluids there. Instead, the tablets work only in the large intestine and have no affect on other organs in the body.

Always consult your doctor, your pharmacy or the leaflet found in-pack in order to obtain complete and up-to-date information on how to take Dulcolax.

If you want an overview of constipation, how laxatives and in particular Dulcolax works, the history of Dulcolax and what other products Dulcolax has within it’s range, then read on:

How Does it Work?

Dulcolax relieves constipation by stimulating the bowel muscles; thus increasing the natural pulsed motions called peristaltic. This encourages natural bowel movement. Moreover Dulcolax acts by accumulating the water into the intestines resulting in the softening of its contents.

Dulcolax tablets usually act reliably within 6-12 hours (suppositories within approximately 30 minutes).

Thanks to a special coating (resistant to gastric and intestinal fluid), the comfort-coated tablets guarantee that the active ingredient is not released until it reaches the large intestine.

Dulcolax suppositories take effect directly in the rectum.

The Dulcolax drops and pearls (Sodium Picosulphate) are converted into the active form by special bacteria present in the large intestine.

Dulcolax is designed in such a way that the active ingredient is transported unchanged through the stomach and small intestine. Neither the gastric acid nor the juices in the small intestine can damage the substance. Contrary to lots of other ingredients, Bisacodyl (Dulcolax tablets) or Sodium Picosulphate (Dulcolax drops, Dulcolax pearls) does not access the blood stream to take effect and therefore no harm to other organs like the liver or the kidney are known. Therefore it is well tolerated.


Product Range

Dulcolax – A complete product range against constipation

Dulcolax laxatives in their different galenic form are not only effective and gentle, but also easy and convenient to take. There are different types of products available, listed below. It might be that the whole range is not available in your country. However, you can ask your pharmacist for advice and he/she will recommend the right product to suit your individual needs.

Dulcolax Tablets

The special comfort-coated tablets are well tolerated. They are very small and easy to take. Depending on the individual rate of transport through the digestive tract, they take effect within 6 to 12 hours on average. Taken in the evening they produce the desired effect the next morning, that is why it is also called an “overnight”-laxative.

As the pH values in the gastrointestinal tract were taken into consideration during the manufacture of the special comfort-coated tablets and when controlling release of the active ingredient, it is important that no products that reduce gastric acid (e.g. milk, antacids) are taken at the same time as Dulcolax. If both products are necessary, these products and Dulcolax should be taken separately with an interval of at least half an hour.


Dulcolax Pearls

This is the latest innovation in the Dulcolax range. They are drops in solid form. The pearls can be individually dosed from 1 to 4 pearls depending on your personal needs. They are soft, small and discreet and can be taken without water. Nevertheless as with all laxatives, it is beneficial to increase your fluid intake. Dulcolax Pearls are effective within 6 to 12 hours.

Dulcolax Suppositories

They are designed for people who need very fast relief from constipation, where oral use has its disadvantages. Dulcolax suppositories usually act reliably within approximately 15 to 30 minutes.

Dulcolax Drops

The drops take effect within 6 to 12 hours and are particularly suitable as a precise, individual minimum required dosage. People with highly sensitive constitutions will only need a few drops. This form is particularly suitable for people who have difficulty swallowing. Like the special comfort-coated tablets and the pearls, the drops are best taken in the evening to allow for an effect the following morning.

If a constipation sufferer needs to undergo antibiotic treatment, special comfort-coated tablets or suppositories should be used rather than drops or pearls, as the intestinal bacteria are unable in this case to convert the active ingredient as required.


The following table summarises the various products within the Dulcolax range together with their particular active ingredients.

Dulcolax Tablets
Active ingredient: Bisacodyl

Dulcolax Pearls
Active ingredient: Sodium Picosulphate

Dulcolax Suppositories
Active ingredient: Bisacodyl

Dulcolax Drops
Active ingredient: Sodium Picosulphate

For further information on laxatives please seek advice from your pharmacist or consult your doctor.

Please note:
Before using Dulcolax, you must read the instructions on the patient information leaflet carefully.


It is now accepted that adequate preparation for most barium enema examinations is essential, particularly if the double contrast technique is to be used (Fisher 1923; 1925; Case, 1937; Welin, 1958). Several studies have shown that preparation with laxatives may be as good as, or better than, colon washout (Sowerbutts, 1960; Prat, Peynon and Prie, 1965; Mitchell, 1967), and may cause the patient far less discomfort. Controlled trials have demonstrated the superiority of a standardised senna preparation (Senokot) over cascara (Duncan, 1957), and of bisacodyl (Dulcolax) over glycerine suppositories (Church, 1959) and over castor oil (Keogh and Fraser, 1958; Popell and Bangappa, 1959; Ritan, 1962).

Recently laxative preparations including the faecal softener and detergent dioctyl sodium sulphosuccinate (Wilson and Dickinson, 1955; Hyland and Foran, 1968) have been introduced and it seemed of value to compare in a double blind trial three of the most widely used laxatives, Senokot DX (sennosides A and B 14 mg), Dulcolax (bisacodyl 5 mg) and a preparation consisting of bisacodyl 5 mg, and dioctyl sodium sulphosuccinate 100 mg (Dulcodos).


Four hundred and fifty sequential out-patients attending the Churchill Hospital for barium enema or intravenous pyelogram (IVP) were allocated on a pre-arranged random sequence to one of the three preparations and the trial was conducted on a double blind basis. The patients were told to take two laxative tablets on the two evenings preceding X-ray examination. On the day of the examination and before any cleansing enema was given, a plain abdominal radiograph 15×12 in. was taken.

The patient’s physical state, mobility, and reliability were assessed and the patient was questioned by an observer, who did not know which laxative had been taken, about the effectiveness of the laxative and any possible side effects. If the patient was undergoing a barium enema, a colon washout with three pints of water containing 10 mg Dihydroxyphenylisatin(P.C.L. 243, Damancy) was then performed and assessment was made by the nurse of the quantity of faeces removed by the washout.

At a later stage the preliminary abdominal radiographs for both barium enemas and IVPs were examined by two radiologists (R.C.S. and F.W.W.), who did not know which preparation had been used, for the presence of gas and faeces in the colon, graded as none, slight, moderate or severe. The films of the barium enema examinations were reviewed at the same time and the presence of any faeces or pathology was noted.


It was decided to exclude 142 patients either because they did not attend or the tablets were not taken or because of clerical errors. The remaining 308 patients were almost equally divided between the three groups (see Table 1).

TABLE I Numbers of patients classified by sex and examination

Treatment Type of X-ray Total
IVP Barium enema  
Senokot DXDulcolax








Totals 181 127 308

In Table II, the results of our assessment of the plain films are shown; there was no significant difference between the three preparations either for gas or for faeces. It will be noted that about 40 per cent of patients have a bowel clear on the preliminary film.

TABLE II Assessment of faeces and gas on plain film

Treatment Faeces Gas
Total Clear % Clear %
Senokot DXDulcolax












A modification of Table II is shown on Table III, where we have classified the results of plain film assessment in terms of “satisfactory”, “unsatisfactory” or “gross faecal residue”. The assessment was satisfactory if the bowel was quite clear or contained only a minimal quantity of faeces insufficient in our view to prevent a satisfactory enema being performed. It was classed as unsatisfactory if the nurse who performed a colon washout recorded considerable faecal material, but the subsequent barium enema examination showed no radiological evidence of faecal contamination.

“Gross faecal residue” was recorded if the colon was loaded with a substantial quantity of faeces, and even after a colon washout there was still considerable faecal residue so that a satisfactory barium enema examination was impossible. It will be seen that as in Table II, results with Senokot DX and Dulcodos were superior to those with Dulcolax, but the differences were not statistically significant.

TABLE III Detailed plain film faecal assessment

Treatment Satisfactory Unsatisfactory Gross faecal residue
Senokot DXDulcolax








Side-effects of the laxatives are shown in Table IV. 70 per cent of the patients were questioned about side-effects, and we have divided these into severe, moderate and minor. We have termed vomiting, griping pains or a trembling with cold sweats experienced by two patients as severe. Pain, nausea and dizziness we have classified as moderate side-effects. Diarrhoea or frequency of loose motions we have termed a “minor” side-effect, though this might be expected if a laxative is taken.

More patients taking Senokot DX had severe side-effects than those taking Dulcolax or Dulcodos. Slightly more Dulcodos patients had more moderate side-effects than those taking Senokot DX. About a third of the patients complained of side-effects; none severe enough to prevent the patient working. Dulcolax had fewer side effects than Dulcodos or Senokot DX, but the difference is not statistically significant. It is interesting that in all groups twice as many women as men had side-effects.

TABLE IV Side-effects

  Senokot DX Dulcolax Dulcodos








TotalNone 3044 2148 3041
Overall total 74 69 71


Although this study has not shown a statistically significant difference in the efficiency of bowel preparation between the three laxatives under trial, it has suggested that Dulcolax is slightly inferior to the other two; on the other hand, there were fewer side effects with this drug. It should be noted that Senokot DX is much cheaper than the other preparations; however, tablets of Senokot tend to fragment if sent by post unless they are well packed.

One finding we consider interesting and important is that 40 per cent of the patients were clear of faeces on radiographs taken after laxative preparation; on the other hand, approximately 40 per cent were too severely contaminated for a satisfactory barium enema to be performed without a preliminary colon washout. It would seem that preparation with a laxative on its own is inadequate in such patients.

However, in 40 per cent nursing time could be saved and the discomfort of a colon washout eliminated where the plain abdominal radiograph shows the colon clear of faeces. In such patients a barium enema may be performed straight away, whilst if moderate faecal contamination is present a colon washout should be undertaken, and if the colon is loaded with faeces the patient may be given further drug and enema preparation, for a colon washout will not clear the colon. It may, however, be wise to examine the distal colon at the first attendance to exclude a low neoplastic or other stricture causing gross faecal obstruction.

A further advantage of the preliminary abdominal radiograph is that in a few cases unexpected pathology may be found. In this series two groups of gall stones, a pelvic tumour and some unexpected renal calculi were discovered in this way. It might be argued that it is difficult to assess the quantity of faeces on the plain film accurately; this has not been our experience. In 84 per cent of the barium enema cases there was agreement between the patients’ own assessment, the opinion of the nurse about the quantity of the faeces removed by the wash-out, and the assessment of the preliminary abdominal radiographs. In the remaining 16 per cent the findings at barium enema closely followed the assessment of the plain radiograph even though the patient and the nurse were under the impression that the laxative had been effective.


1. No significant difference is found between Dulcolax, Senokot DX and Dulcodos in their effectiveness for bowel preparation for radiological examination; the latter two drugs appear to be slightly superior, but they suffer from the disadvantage of producing slightly more side-effects than Dulcolax.

2. It is suggested that a preliminary abdominal radiograph before a barium enema examination is of considerable value, for at least 40 per cent of patients have a sufficiently clear bowel after laxative preparation as not to require a colon washout. On the other hand, about 40 per cent are too contaminated for a satisfactory barium enema examination unless a colon washout is performed, and a small minority can be distinguished on the preliminary radiograph, who cannot be adequately prepared even with the aid of a colon washout.

Br. J. Radiol, 1970, 43, 245-247

The Food and Drug Administration of the USA (FDA)

Bisacodyl, the active ingredient of Dulcolax, is “safe and effective”.
Boehringer Ingelheim USA completed extensive tests with Bisacodyl in 1999 under the supervision of the American health authorities (FDA) in an effort to investigate the carcinogenic and mutagenic potential of drugs. The FDA published its assessment in 2000: “From all the data available there are no signs to suggest a risk of cancer in humans if Bisacodyl is taken as recommended.” This data thus supports the allocation of Dulcolax to group I OTC products in the USA as safe and effective.

Bisacodyl absorption study:

This study was designed to investigate the absorption of Bisacodyl and the blood level patterns. It also attempted to correlate this with the evacuation effect. The study concluded: There is no correlation between the laxative effect of Bisacodyl and the blood level. According to the present findings, the laxative effect of the comfort-coated tablet and suppository is triggered by an interaction or direct contact of the substance in the lower part of the intestine.

American Gastroenterological Association (AGA) on 21 May 2000: New guidelines on the management of constipation

Dulcolax is the product of choice:

  • for constipation with delayed intestinal transport: Dulcolax or fibre or mineral salts.
  • for constipation without delayed intestinal transport: Dulcolax where fibre or mineral salts are ineffective
  • for disturbed rectal evacuation: behaviour therapy and biofeedback combined with administration of Dulcolax or fibre or mineral salts.

Frequently Asked Questions

Is Dulcolax available everywhere?

Yes. Dulcolax is available across the world, mainly in pharmacies. Thanks to its safety and reliability, it is a frequently requested and recommended product for constipation.Is it wise to use Dulcolax every day?

No. Once Dulcolax has been used successfully, the intestine is completely empty. It takes 2-3 days for the intestine to fill sufficiently to stimulate evacuation naturally. It is not therefore wise to force evacuation on a daily basis. In medical terms, stool frequency of 3 times a day to 3 times a week is normal.

Has there ever been adverse events by using Dulcolax?

There might be cases of abdominal discomfort including cramps and abdominal pain. Sometimes diarrhoea has been observed.

Is it necessary to increase the recommended dose of Dulcolax?

No. Dulcolax is reliable in the generally recommended dose. This has been demonstrated by studies in paraplegics who used Dulcolax regularly (every 2 to 3 days) for 2 to 34 years.

Can Dulcolax be taken at the same time as contraceptives?

Yes. Dulcolax special comfort-coated tablets, pearls, suppositories or drops do not develop their digestant effect until they reach the large intestine. Unlike some other products, for instance laxatives that take effect in the small intestine such as Glauber’s salt, Epsom salt or caster oil, Dulcolax products are not known to impair the transport of “pill hormones” from the small intestine to the bloodstream.

Is Dulcolax suitable for losing weight?

No. Dulcolax is not a weight loss product.

Is Dulcolax addictive?

No. The active ingredients of Dulcolax products, Bisacodyl or Sodium Picosulphate do not penetrate the so-called blood-brain barrier and thus no addictive potential that could lead to dependence have been reported.

Has Dulcolax been investigated for carcinogenic potential?

Yes. In an effort to investigate the cancer risk and potential genomic damage, extensive tests with Bisacodyl were conducted under the supervision of the American health authorities (FDA) and Boehringer Ingelheim USA in 1999. The conclusion of the FDA in spring 2000: “From all the data available, there are no signs to suggest that Bisacodyl presents a cancer risk if used as instructed.” This data thus supports the allocation of Dulcolax to Group I of OTC products in the USA as safe and effective.

Are there differences in the quality of the pure substance Bisacodyl and Dulcolax?

Yes. It is known that the mode of action of a substance can be modified and optimised by pharmaceutical technology. Even drugs with the same content of active ingredient but processed differently when made into drugs (galenics) can show considerable differences in effect.

Dulcolax is the original. The active ingredient Bisacodyl stems from research at Boehringer Ingelheim.

Dulcolax is designed in such a way that the active ingredient is transported unchanged through the stomach and small intestine. Neither the gastric acid nor the juices in the small intestine can damage the substance. It only takes effect in the large intestine. This special design virtually avoids stimulation of the gastric or small intestinal muscles, absorption in the bloodstream, conversion of the substance in the liver and diarrhoea.

Is there a reason for women suffering from constipation much more often than men?

Yes. Women suffer from constipation three times more frequently than men do. This is connected with their sex hormones and uterus. Hormone researcher, Dr Johannes Huber, Professor at the University Teaching Hospital for Gynaecology in Vienna, explains why that is so: “Constipation is a sex-specific disorder due to a woman’s hormonal fluctuations!”

When the uterus expands during pregnancy, the organ is “immobilised” by hormones to avoid premature contractions. To this end, the body uses nitrogen monoxide, the formation of which is estrogen-dependent. This immobilisation of the uterus also affects the intestinal muscle, causing constipation.

Female hormones act in a similar fashion when the balance is disturbed during the second half of the cycle. Here again constipation is pre-programmed.

During the menopause the hormone progesterone immobilises the uterus. These natural changes and/or supply of artificial hormones to counter the effects of the menopause can frequently cause constipation in elderly women.

“Patients whose intestinal transit time is slowed down by hormonal disturbances,” explained Prof. Joachim F. Erckenbrecht, senior registrar for internal medicine and gastroenterology in Duesseldorf, “require treatment with medicines that stimulate the intestinal nervous system and hence transport functions”

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