Oral Drugs for Diabetes
The search for an effective oral drug for diabetes has been going on since a long time. Unproved claims are made from time to time that some herbs are effective or even curative in diabetes. Every country boasts of some "herbal cure" for diabetes.
Some drugs like salicylates (aspirin belongs to this group) in a large dose, bring down the blood glucose level. But such drugs do not have any practical value in the treatment of diabetes.
Insulin was the first really effective drug in the treatment of diabetes. Since it has to be injected, the search for oral antidiabetic drugs continued, even after the efficacy of insulin was established.
Oral drugs for diabetes belong to five groups: sulphonylureas, akin to the sulphonamides, meglitinide group, biguanides, thiazolidinediones and alpha-glucosidase inhibitors.
Names of drugs
All drugs have a single official (approved or non-proprietary) name and one or more brand (proprietary) names. While brand name of particular drug may vary from country to country or within the same country, the official name is usually the same. A diabetic should familiarize himseif with the official name so that in event of shortage or withdrawal of a particular brand in the market, he can use an alternate brand of the same drug.
As the same or different brands of a particular drug may be available in different strengths, the diabetic should know the strength of the drug too.
The brand names of oral drugs for diabetes and their combinations, are too numerous to be tabulated or listed. The diabetic should familiarize himself or herself, with the official names of the drugs he/she is taking.
Sulphonylureas
Actions
These drugs secrete insulin by binding to receptors on beta cells. They possibly increase the number of insulin receptors and magnify the effects of available insulin. They can he effective only in presence of functional beta cells.
Sulphonylurea Preparations
| Sulphonylurea | Strength available (mg) | Average Dose (mg) | Max Dose (mg) |
Duration of action (hours) | Doses per day |
| Tolbutamide | 500 | 1500 | 3000 | 4.5-6.5 | 1-3 |
| Chlorpropamide | 100, 250 | 250 | 500 | 60-72 | 1 |
| Glibenclamide* | 2.5,5 | 7.5 | 20 | 24 | 1-2 |
| Glipizide | 5 | 10 | 40 | 15-24 | 1-2 |
| Gliclazide | 40,80 | 160 | 320 | 16-24 | 1-2 |
| Gilmeperide | 1,2 | 4 | 8 | 24 | 1 |
* Referred to as Glyburide in some countries.
Who are benefited by these drugs ?
These drugs arc useful in the treatment of persons with type 2 diabetes, not responding to diet and exercise. Persons who have developed diabetes after the age of 35 years, those having diabetes for less than 5 years, those who need less than 30 units insulin, whose fasting blood glucose level is less than 300 those who are of normal weight or who are obese and who never had diabetic coma or ketosis are suitable candidates for these drugs.
Persons who have developed diabetes at an young age, those with a severe infection or injury, those going for a major operation, and pregnant and lactating diabetics are not treated with these drugs. These drugs are understandably ineffective in the treatment of diabetes secondary to removal or destruction of the pancreas. These drugs are contraindicated in persons with impaired liver and kidney function and in those predisposed to hypoglycaemia. These drugs are not given to people with an allergy to the sulfonamides.
Side effects
These drugs can give rise to hypoglycaemia. This is more likely to occur with long acting sulphonylureas like glibenclamide and chlorpropamide, and in the elderly and those with poor nutrition and impaired kidney function.
These drugs may produce minor stomach upset, nausea, indigestion, vomiting, malaise, and dizziness. Sometimes they may give rise to rashes and itching usually in first 6-8 weeks of the treatment. A person taking chlorpropamide may develop flushing of the face, throbbing headache, difficulty in breathing, vomiting, if he/she has an alcoholic drink. Water retention and low serum sodium level may occur with chlorpropamide. These drugs may rarely give rise to liver or blood disorders.
Many drugs interact with these drugs. The effect of the sulphonylureas may be enhanced if the person, in addition, takes some pain relieving drugs, drugs reducing blood clotting, sulfonamides or alcohol. As a rule, a diabetic should inform his/her doctor, all the drugs which he/she is taking.
Some Practical Points
Sulphonylureas are generally to be taken before meals. Long acting sulphonylureas, like chlorpropamide and glimeperide are taken with breakfast. The likelihood of sulphonylureas interfering with other drugs such as aspirin, certain antihypertensives, antiepileptics, alcohol is maximum with tolbutamide and chloropropamide. Glipizide and gliclazide are the preferred drugs, if at all, for mild impairment of kidney function. A short acting drug like glipizide is preferred in the elderly or those with inadequate or irregular diet, an intercurrent illness or when certain other drugs are being given.
The efficacy of all sulphonylureas is virtually the same, hence if one of them is ineffective, it is very unlikely that another would prove effective in the long run.