cc, and can dispense up to 3/io cc, or 30units.
The insulin's strength is designated U-100, meaning "100 units per cc." Inthe United States and Canada, this is the only insulin concentration sold, so you need not specify thestrength when you purchase.
Other insulin strengths, such as U-40 and U-80, are sold in other countries, and the scaleson the sy ringes in these countries are designed for these other strengths.
Aspe cial strength, U-500, isavaUable toyour physician in theUnited States, upon request from the manufacturers, for special appUcations.
The sy ringes for U-40 andU-80 strengths are notsold in theUnited States.
Ifyou travel overseas and happen to lose or misplace your insulin, you may beunable tosecure the U-100 strength locaUy.
You can make the best of this by purchasing U-40 or U-80 insulin, together with U-40 or U-80 syringes.
You should draw yourusual doses in units into the newsyringes with the newinsulin.
CARING FOR YOUR INSULIN
Insulinisstable until the expiration dateprinted on the label, if refrig erated.
Aslight loss of potency may occur if insulin is stored at room temperature longer than 30-60 days.
This isespeciaUy true of glargine (Lantus) insuUn, which maylose a significant amount of potencyafter 60days at room temperature.
It isbest stored in a refrigerator.* Insulin can become partiaUy deactivated with or without a change in its appearance, leading to unexpectedly elevated blood sugars.
When I receive a distress caU from a patient who has had higher than usualblood sugars for several days, I aska number of questions in or der to determine the source of the blood sugar elevation.
Have there been dietary indiscretions?
Isthere a possible infection?
Or mightthe insulin be somewhat deactivated, perhaps by reuse of syringes (page 257)?
Even sUght cloudiness of a clear insulin isa certain sign of deac tivation.
So is the appearance of visible clumps within, or a gray pre cipitate on the waU of, a vial of NPH insuUn (normaUy cloudy) that wiU not disappear whenit's shaken.
Deactivation of insulin, however, may not be possible to distinguish simply bylooking.
If dietor infec tion seems unlikely to be the source of the blood sugar elevation, I
*The manufacturer of Lantus isoverly cautious and recommends that it be dis carded at 30 days after initial use , even if refrigerated. This is a very profit- effective directive.
Important Information About Various Insulins 267
therefore advise my patient to discard aU insulin currently in useand to utilize fresh vials, evenif the insuUn looksokay. Here are some simple rules for routine care of your insulin:
• Keep unusedinsulin in a refrigerator untU you are ready to useit for the first time.
Vials in current use maybe kept at roomtem perature for convenience, but Lantus (and possibly detemir and gluUsine) is best stored in the refrigerator. • Never aUow insulin to freeze.
Even after it thaws out, it may no longer possess its fuU strength.
If you suspect it may have frozen, discard it. • If yourhome reaches temperatures above 85°F (29°C), refriger ateaU your insulinwhen not in use.
If your insulin hasbeen ex posed to temperatures in excess of 99°F (37°C) for more than 1 day, discard it. • Do not reuse your insulin syringes (page 257). • Do not put insulin in prolonged sunUght or in closed, unat tended motor vehicles, glove compartments,or car trunks.
These areas can become overheated on a sunny day, even in winter.
If you inadvertently leave insulin in a hot vehicle, discard it.
This rule also appUes to blood sugar test strips. • Donot routinely keep insulin close to yourbody, asin shirtpockets. • If you keep yourcurrently usedinsuUn out ofthe refrigerator, af ter it warms to room temperature use a felt-tipped marker to mark the date when the vialwas first removed from the refriger ator.
Cover the marking with clear tape to prevent erasure.
Dis cardaU vials of glargine, gluUsine, and detemir whenever 30-60 days have elapsed foUowing the marked date. • When you invertyourinsulin vial to fill yoursyringe, observe the level of insuUn.
When the level drops belowthe loweredgeof the label on the inverted vial, discard the vial.
This is especiaUy nec essarywith normaUycloudy insulins (NPH) becausethe concen tration of active particles may change asyou use it up. • If you plan to travel to anarea with warmclimate where you may not be able to refrigerate your insulin,consider a product caUed Frio, mentioned in Chapter 3,"Your DiabeticTool Kit." This is a smaU fabric waUet with peUets sewninto the lining.
It's avaUable in five sizesin the United Kingdom and two in the United States.
When the waUet is soaked in water for 15 minutes,the peUets wiU form a gel.
As the water in the gel slowly evaporates through the
268 Treatment
pores of the wallet, it will keep insulin at a safe temperature with out recharging for at least 48 hours at a surrounding air temper ature of 100°F (38°C).
HOW INSULIN AFFECTS YOUR BLOOD SUGARS OVER TIME
It's important for you to know whenyour insulin wUl begin to affect your blood sugar and whenit will finish working.
This information is printed on the insert in the insulin package.
The published informa tion, however, maybe inaccuratefor patients on our regimen.The rea son for this is that we use very small doses of insulin, while most published data are based upon much larger doses.
As a rule, larger nonphysiologic doses tend to start workingsooner and finish working later than smaller doses.
Furthermore, the action time of an insulin wiU vary somewhat from one person to another and from smaller to larger doses.
Nevertheless, Table 17-1 is a reasonable guide to the ap proximate starting and finishing times of the insulins we recommend when used in physiologic (as opposed to the usual industrial) doses.
Your response may not follow a typical pattern, but at least this table can serve as a starting point.
Insulin action wiU be speeded considerably if you exercise the re gion of your body into which you injected.
As a consequence, it maybe, for example, unwise to inject long-acting insulin into your arm on a day that you lift weights or into your abdomen on a day that you do sit-ups.
A NOTE ABOUT MIXING INSULINS
In a word, Don't. Two different insulins should never be mixed , with the single exception of the specific situation discussed on page 378. Other than that, mixing of insulinshas no usefulpurpose, even though it is advocated by the ADA and even though you can purchase mix tures that are marketed by pharmaceutical companies. Mixing a long-acting insulin with a rapid-acting one results in an insulin that no longer has either the long- or rapid-acting properties.
Important Information About Various Insulins 269
TABLE 17-1 APPROXIMATE ACTION TIMES OF PREFERRED INSULINS
Action time after injection*
Generic name U.S. brand Action Action of insulin Abbreviation name Designation starts ends
Aspart* A Novolog Most-rapid- 20 minutes 6-7 hours
Lispro* H Humalog acting (but assume
Glulisine G Apidra 5 hours)
Regular,or R Humulin R Rapid-acting 45 minutes 8-10 hours or crystalline1 Novolin R more (but assume 5 hours)
NPH*** N Humulin N Intermediate- 2-3 hours 12 hours if
(cloudy) Novolin N acting injected in the morning; 8 hours if injected at bedtime
Detemir* D Levemir Long-acting Slowlyover 18 hours if
4 hours injected in the morning; 8-9 hours if injected Glargine LAN Lantus at bedtime
(apparent)
Doses exceeding 7 unitswill usually start sooner, last longer, and act less predictably than smaller doses. See page 304. f Aspart is not quite as rapid in itsaction as lispro or glulisine. *Canbe diluted for usebychildren (see page 272). ** Doses of NPH that exceed 7 units mayhave a peakof action at about 8 hours after in jection.
ABBREVIATED DESIGNATIONS FOR THE VARIOUS INSULINS
When you're filling in the information on your Glucograf data sheets, it will be more convenient for you and your doctor if you use the abbreviated designations shown in the "Abbreviation" column of Table 17-1 , A, H, G, R, N, D, or LAN , instead of the full names.
270 Treatment
Since it's implied, you also needn't write out the word "units" when noting insulin doses. Seven units of regular insulin would abbreviate as "7 R," and so on. If you forget these abbreviations, they are printed in the upper right corner of your Glucograf III data sheet.
ARE THE PREFERRED INSULINS EQUALLY POTENT?
If we ignore the differences in timing, 1 unit of each of these insulins will have the same effect upon blood sugar as 1 unit of any of the oth ers, with the striking exception of lispro, glulisine, and aspart. These insulins are about 50 percent more potent than regular, the only re maining rapid-acting, true human insulin.
DO YOU NEED A PRESCRIPTION FOR INSULIN?
Yes and no. Aspart, lispro, glulisine, detemir, and glargine require a prescription from your doctor in the United States. NPH and regular may be purchased without a prescription in most states. Local regula tions are subject to change.
WHY DO WE USE THE LONGER-ACTING INSULINS?
Glargine and detemir, the clear longer-acting insulins, serve a purpose different from that of the rapid-acting insulins.
Indeed, for our regi menstheyhave but one principal task , to keep bloodsugarfrom ris ing while fasting (see the discussions of gluconeogenesis and the dawn phenomenon, pages 92-93).
They are our basal insulins.
They're not intended to preventthe bloodsugarriseaftereating.
Furthermore, they are not used to lower a blood sugar that is too high , they work too slowly for this.
A secondary purpose of longer-acting insulins in mild type 2 diabetes is to help delay or prevent beta cell burnout.As you'll see later, we may use a rapid-acting insulin to cover meals, whether or not the longer-acting insulins are used to cover the fasting state.
Which insulin to use, and when, depends upon blood sugar profiles.