Insulin Flashcards

1
Q

Instability of insulin

A

Drug instability may be advantageous to certain individuals, e.g., insulin
Numerous accidental insulin overdoses
Prolonged hypoglycemia light threatening
Less frequent agent of suicide in both diabetics and non-diabetics
Insulin used as an instrument of homicide
Rare occurrence
Marks review of the literature found only 66 cases worldwide
Conviction only 31 cases, with the additional weapon used in 11 of the cases

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2
Q

Nurse Kenneth Barlow

A

1st. case of murder facilitated by insulin in england
“You could commit a perfect murder with insulin. It cannot be traced”
Wife was pregnant and neither wanted a baby
Gave her injections to “induce an abortion”
Found “drowned”…
Pathologist noted four injection sites in her buttocks
Excised for analysis
Insulin detected; not a diabetic, thus no need for insulin
Barlow gave wife insulin, instead of abortifacient, to make her stuporous and complaisant
Placed her comatose in the tub – slide under the water and drowned

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3
Q

Martha sharp crawford von bulow

A

Known as Sunny von Bulow
 American heiress, socialite, and philanthropist
o Found in coma
o Husband, Claus von Bulow

 Convicted of attempting murder to her (1980) by insulin overdose
o Second trial found him not guilty
 Experts opined that there was no insulin injection
 Symptoms attributed to over-use of Rx drugs
o Sunny von Bulow lived almost 28 years in a persistent vegetive state until her
death in a New York nursing home on dec 6, 2008

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4
Q

proinsulin

A

o Two peptide chain molecules (insulin) linked by connecting peptide [C-peptide]
o Synthesized by the B-cells of the pancreas

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5
Q

what do you see when you increase glucose

A

Causes a proteolytic cleavage of the proinsulin molecule
o T=yields the active insulin molecule and the inactive c-peptide in a molar ratio
of 1:1

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6
Q

C-peptide

A

 C-peptide is produced simultaneously with insulin in the insulin precursor – proinsulin
 In proinsulin, C-peptide is located as if connection insulin A and B chains
 So, it is called “c(onnecting) peptide”

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7
Q

plasma half life

A

Plasma half-life of insulin is ~5-8 minutes
o Degraded by red-cell proteolytic enzymes, in kidney and liver

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8
Q

C-peptide half life

A

10-20minutes
degraded by kidneys

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9
Q

what can happen if patient previously exposed to exogenous insulin

A

may develop antibodies to insulin
degrade degration
leads to falsely high or low values

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10
Q

what is the main difference between endogenous and exogenous insulin

A

Major difference between commercial insulin and endogenous insulin is the absence of
C-peptide

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11
Q

what do you expect with large dose of exogenous insulin

A

elevated insulin and suppressed C-peptide
o Suppression of C-peptide due to negative feedback system
 Stops cleavage
o Hypoglycemic effect of insulin potentiated by alcohol

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12
Q

IS insulin stable

A

fairly stable at 4C
significant degaration notes at 37V four to five days

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13
Q

normal ranges of insulin

A

serum: 0-22
C-peptide.08-4.6

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14
Q

normal fasting regions for insulin

A

5-75

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15
Q

fatal insulin ranges

A

800-3200

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16
Q

what ratio identifies an insulin overdose

A

molar-ratio od greater than 1l

17
Q

what tubes for insulin

A

red-top tubes

18
Q

C=peptide degrade?

A

yes in serum or improperly collected plasma

19
Q

interpretive challenges

A

High degree of suspicion and rapid/proper sample collection and analysis
 Hemolysis
o Release of proteolytic enzymes will lower insulin and C-peptide concentrations
 Stability
o Instability at elevated temperatures
 Assays may cross-react with insulin antibodies