Test 2 Diabetes MedChem Flashcards
1
Q
Insulin:
A
- Hormone
- Secreted by β cells of islet of Langerhans
- In the liver and muscle tissues, insulin promotes the storage of excess glucose as glycogen.
- Composition (51 amino acid peptide):
- A chain (21-amino-acid)
- B chain (30-amino-acid)
- Linked by disulfide bond between the 2 cysteines
- Exists as dimers and hexamers (can form an interaction with zinc – concentration dependent)
- To be biologically active, insulin must be in monomeric form
2
Q
Insulin Preparations
A
- Short acting
- Rapid acting
- Intermediate acting
- Longer-acting
3
Q
Short-acting Insulin
A
- Short-acting:
- Regular Insulin (Humulin R, Novolin R)
- Onset of Action: 0.5-1 h; Peak: 2-4 h;
- Duration: 6-8 hrs
- Regular Insulin (Humulin R, Novolin R)
4
Q
Rapid-Acting Insulin
A
- Rapid-Acting - Products: B28 and B29 are changed in most of these agents à may alter the secondary structure (fewer beta sheets)
- Lispro (Humalog) – lysine + proline added
- Change: B28 Pro → Lys; B29 Lys → Pro
- (Lysine and proline are switched around)
- Aspart (NovoLog) – asparagine added
- Change: B28 Pro → Asp
- Glulisine (Apidra)
- Change: B3 Asn → Lys; B29 Lys → Glu
- Lispro (Humalog) – lysine + proline added
- Onset of Action: 15 min (These products predominantly exist as monomers → have a quick onset of action)
- Peak: 1 h; Duration: 4 hrs
5
Q
Intermediate-acting Insulin
A
- Intermediate-acting:
- Neutral protamine Hagedorn (NPH) insulin (Humulin N, Novolin N)
- Protamine (highly + charged) and regular insulin
- Protamine contains arginine – used in heparin overdose (forms an ionic interaction)
- Protamine (highly + charged) and regular insulin
- Cloudy appearance – has poor solubility (Not completely soluble)
- Onset of Action: 2 hrs (Onset takes longer than regular insulin because it must dissociate from the protamine)
- Neutral protamine Hagedorn (NPH) insulin (Humulin N, Novolin N)
- Peak: 4-8 h; Duration: 12-18 hrs
6
Q
Longer-Acting Insulins
A
Glargine (Lantus)
Detemir (Levemir)
Degludec (Tresiba)
Ryzodeg
7
Q
Glargine
A
- Longer Acting Insulin
- glargine (Lantus)
- Change: A21 Asn → Gly
- Add: B31 Arg and B32 Arg
-
Clear solution in bottle (pH 4).
- When injected, at body pH (7.4) it precipitates
- (isoelectric point is ~6.8, which is lower than physiologic pH → leads to longer DOA )
- DONT mix with formulations that have a different pH
- Onset: 2 hrs, DOA: 20-24 hrs
- glargine (Lantus)
8
Q
Detemir
A
- Longer Acting Insulin
- Detemir (Levemir)
- Remove: B30 Thr
-
Add: C14 fatty acid (myristic acid=increased lipophilicity) to B29 Lys.
- Increases lipophilicity
- Fatty acid side chain binds to non-covalently plasma albumin to produce a longer action
- Detemir (Levemir)
- Onset: 2 hrs, DOA: 12-24 hrs
9
Q
Degludec
A
- Longer Acting Insulin
- Degludec (Tresiba) – possible ultra-long acting (up to 42 hours)
- Remove: B30 Thr
- Add: glutamic acid and a hexadecanedioic fatty acid (increases lipophilicity causing it to be bound to proteins which gives long duration)
- Degludec (Tresiba) – possible ultra-long acting (up to 42 hours)
- Onset: 1 hr
- DOA: >24hrs
10
Q
Ryzodeg
A
- Longer Acting Insulin
- Ryzodeg
- (70% degludec and 30% aspart)
11
Q
Inhaled insulin
A
- Inhaled insulin (Afrezza)
- Dry powder formulation of regular insulin
- Approved in adults
- Peak level is reached in 12 – 15 min; quicker onset of action
- Adverse effects: cough
- Contraindicated in smokers and COPD
12
Q
· Medications That May Affect Glycemic Control: hyperglycemic activity
A
- Medications with hyperglycemic activity (give higher dose of insulin)
- Glucocorticoids
- Niacin
- Diuretics (thiazides)
- Hydantoins (phenytoin)
- Atypical antipsychotics
13
Q
· Medications That May Affect Glycemic Control: hypoglycemic activity
A
- Medications with hypoglycemic activity (give lower dose of insulin)
- Oral antidiabetic agents
- Angiotensin-converting enzyme inhibitors
- Salicylates
14
Q
Q: Which of the following insulin formulations when administered forms a precipitate in the body?
A
Glargine (Lantus)
15
Q
What is GLP-1?
A
- An incretin hormone; 37–amino acid peptide
- Secreted in gut from L-cells
- ↑ insulin secretion, ↓ glucagon release, delays gastric emptying (not direct action), ↓ food intake, and normalizes fasting and postprandial insulin secretion.
- Secreted in gut from L-cells
- Limited/ No clinical applicability: Rapidly hydrolyzed by dipetidyl peptidase IV (DPP-IV): t½= 1 to 2 min
- Not available as a drug because it can be rapidly hydrolyzed by DPP-IV
16
Q
Ways to increase GLP-1
A
- GLP-1 agonist, DPP-IV inhibitor
- Rationale: GLP-1 agonists or DDP-IV inhibitors are effective agents to control blood glucose levels in diabetic patients
- GLP-1 is hydrolyzed by the DiPeptidyl Peptidase IV (DPP-IV) enzyme
- GLP-1 is rapidly inactivated by the enzyme dipeptidyl peptidase IV (DPP-4
- Both GLP-1 and glucagon are products derived from preproglucagon, a 180–amino acid precursor with five separately processed domains (Figure 43–9) (Drucker, 2006). An amino-terminal signal peptide is followed by glicentin-related pancreatic peptide, glucagon, and glucagon-like peptide 2 (GLP-2).
- Rationale: GLP-1 agonists or DDP-IV inhibitors are effective agents to control blood glucose levels in diabetic patients
17
Q
GLP-1 Receptor Agonists
A
- GLP-1 agonists or DDP-IV inhibitors are effective agents to control blood glucose levels in diabetic patients
- Exenatide (Byetta)
- Liraglutide (Victoza)
- Albiglutide (Tanzeum)
- Dulaglutide (Trulicity)
- Lixisenatide (Adlyxin)
- DDI: May delay the absorption of other medications
- Boxed Warning: increased risk of thyroid tumors
18
Q
Exenatide
A
- GLP-1 Receptor Agonist
- Exenatide (Byetta)
- Synthetic version of Exendin-4 (natural product synthesized from saliva of gila monster?)
- 53% homology to human GLP-1
- Synthetic version of Exendin-4 (natural product synthesized from saliva of gila monster?)
- t½ elimination
- IR (twice daily) formulation: 3 -4 hours
- ER (weekly) formulation (Bydureon)[Microspheres]: ~2 weeks
- Longer half-life → less frequent dosing
- Contains microspheres
- Metabolism and elimination: glomerular filtration and proteolytic degradation
- Severe renal impairment: should not be used
- Exenatide (Byetta)
19
Q
liraglutide
A
- GLP-1 Receptor Agonist
- Liraglutide (Victoza)
- 96% homology to human GLP-1
- Arg34®Lys; C16 fatty acid chain attached to Lys26
- BA: SubQ: ~55%
- PB: >98% - fatty acid chain can interact w/ proteins
- Metabolism: proteolytic degradation
- t ½ elimination: 13 h; Once-daily administration
- Fatty acid chain binds to albumin and is slowly released
- Renal Impairment. No dose adjustment, but use with caution
- Liraglutide (Victoza)
20
Q
Albiglutide
A
- GLP-1 Receptor Agonist
- Albiglutide (Tanzeum)
- Newer Drug (2014)
- GLP-1 dimer(2 GLP-1) fused to albumin (fusion protein)
- Covalent interaction
- Amino acid substitution Ala (GLP1) to Glu (Albiglutide)
- Dimer improves receptor interaction in the presence of albumin
- t ½= 5 days (much longer)
- Administered once-weekly
- Metabolism: proteolytic degradation
- Decreased renal clearance due to bigger size
- Renal impairment: No dose adjustment
- Albiglutide (Tanzeum)
21
Q
Lixisenatide
A
- GLP-1 Receptor Agonist
- Lixisenatide (Adlyxin)
- Newer Drug (2016)
- Exendin-4 AA 38 proline is deleted and six lysine residues are added
- t ½ elimination: about 3 hours
- Once-daily administration
- Metabolism: proteolytic degradation
- Mild to moderate renal impairment: No dose adjustment
- Severe renal impairment: Don’t give or adjust
- Lixisenatide (Adlyxin)
22
Q
Dulaglutide
A
- GLP-1 Receptor Agonist
- Dulaglutide (Trulicity)
- Newer Drug (2014)
- GLP-1 analog + Linker + Modified IgG4 Fc Domain
- Dulaglutide (Trulicity)
- Absolute bioavailability: 47% - 65 %
- t ½ elimination: 5 days
- Once-weekly administration
- Metabolism: Possible proteolytic degradation
-
Renal impairment: No dose adjustment
- Peptide fused to IgG → higher MW → longer t 1/2
- T 1/2 of native GLP-1 = minutes
23
Q
What is Amylin?
A
- 37–amino acid peptide
- Released from pancreatic beta cells
- Cosecreted with insulin
- Role:
- Delayed gastric emptying and suppression of glucagon secretion
- Also regulates food intake (appetite center in brain)
- Amylin itself is unsuitable as a drug because
- Aggregates
- Insoluble in solution