Absorption of Drugs Part 1 — Transcript

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1. 0:00hi there and welcome back to an
2. 0:01understanding medications in this lesson
3. 0:04we'll be aiming to get a general
4. 0:05understanding of the first process of
5. 0:08pharmacokinetics specifically the
6. 0:10absorption of drugs
7. 0:12there's many ways in which we can
8. 0:14administer medications for instance if
9. 0:16we took an oral tablet that tablet's
10. 0:19going to go down into the stomach break
11. 0:21up into millions of little pieces it's
12. 0:23going to wind up going into the liver
13. 0:27it's going to go into the venous system
14. 0:29into the right side of the heart into
15. 0:32the lungs into the left side of the
16. 0:34heart and then finally onto systemic
17. 0:36arterial circulation where it's going to
18. 0:38be able to do its actions now that's a
19. 0:41long way
20. 0:42but if you administered glycerol
21. 0:44trinitrite are sometimes called
22. 0:46nitroglycerin for Angina sublingually or
23. 0:49under the tongue or if you administered
24. 0:52it by transdermal patch or if you
25. 0:54administered another medication by
26. 0:56suppository into the lower portion of
27. 0:59the rectum all of those modes of
28. 1:02administration will go directly into the
29. 1:05venous system circulation then it would
30. 1:08only have to go to the right side of the
31. 1:10heart into the lungs into the left side
32. 1:13of the heart and onto systemic arterial
33. 1:16circulation
34. 1:18and if you injected a medication into
35. 1:20the subcutaneous fat that's going to go
36. 1:24into the interstitial spaces around the
37. 1:27adipose or fat tissue and then it's
38. 1:29going to go into the venous circulation
39. 1:32once again
40. 1:33but think about what happens when you
41. 1:35administer an anesthetic into the lungs
42. 1:38the anesthetic would go directly down to
43. 1:42the alveoli where it would enter into
44. 1:45the capillaries of the lungs the
45. 1:48anesthetic would then just need to go to
46. 1:51the left side of the heart and onto
47. 1:53systemic arterial circulation so that is
48. 1:56one of fastest routes of administration
49. 2:00each of those modes of administration is
50. 2:03going to need to be absorbed into the
51. 2:06blood system in fact the only modes of
52. 2:09administration that don't need to be
53. 2:11absorbed are the intravenous
54. 2:13administration or the intra-arterial
55. 2:16administration because those types of
56. 2:19administration place the medication
57. 2:21directly into the blood
58. 2:25one thing to note about those different
59. 2:28methods of administration is that they
60. 2:31will vary with respect to the amount of
61. 2:34time that they take to fully get into
62. 2:36systemic circulation and therefore their
63. 2:39Peak concentration in the blood or their
64. 2:43concentration Max or C-Max is going to
65. 2:48vary as well for instance the absorption
66. 2:51of orally administered medication is
67. 2:53spread over time and has quite a low
68. 2:56C-Max conversely the same dose of an
69. 3:01intravenously administered medication or
70. 3:04a medication that is administered by
71. 3:06inhalation into the lungs is going to
72. 3:09have a fairly rapid spike in the C-Max
73. 3:14and this is quite important so I'm going
74. 3:16to stop right now so that we can apply
75. 3:18our knowledge of these different points
76. 3:20about absorption with a quick quiz
77. 3:22and then we'll finish up with Part B of
78. 3:25the absorption lesson just after that
79. 3:27quick quiz
80. 3:31we've just explained that there's a big
81. 3:33difference between the concentration Max
82. 3:36or what we call C-Max between a
83. 3:39medication that is orally administered
84. 3:42versus a medication that is
85. 3:44intravenously injected or administered
86. 3:48by inhalation
87. 3:50the absorption of oral medications will
88. 3:53be spread over time much more
89. 3:56so let's think about what that would
90. 3:59mean for instance with side effects and
91. 4:02potential overdose
92. 4:04looking at the graph of the
93. 4:06concentration Max between the different
94. 4:09modes of administration which of these
95. 4:12do you think would have a greater
96. 4:14potential for side effects
97. 4:19and you were correct if you had said
98. 4:21that there was a greater risk of
99. 4:23Overdose and side effects with the types
100. 4:26of administration that allow the
101. 4:28medication to enter the systemic
102. 4:31circulation the fastest
103. 4:34so there's a greater potential for
104. 4:36overdose with the medications that are
105. 4:38intravenously injected or administered
106. 4:41by inhalation
107. 4:44most medications bind to the receptor or
108. 4:48enzyme that they're supposed to bind to
109. 4:50but they also have some effect on other
110. 4:54receptors or enzymes and that's the
111. 4:57reason for many of the side effects of
112. 4:59the medication when the medication is in
113. 5:03high concentration it's much more likely
114. 5:06that the drug is going to bind to and
115. 5:09affect the receptors or enzymes that
116. 5:12it's not supposed to bind to
117. 5:14another thing I want you to note with
118. 5:16these graphs is the speed at which the
119. 5:19drug is metabolized and eliminated from
120. 5:22the system especially in the first
121. 5:24instance when that concentration is the
122. 5:27highest take a look at these graphs and
123. 5:30explain which one you think has the
124. 5:32steepest fall in the drug concentrations
125. 5:35and what you think that means about the
126. 5:39metabolism of drugs
127. 5:45and you were correct if you had said
128. 5:47that the drug that has the greatest
129. 5:49C-Max or concentration Max initially has
130. 5:53the steepest fall in drug concentrations
131. 5:57meaning that they are the ones that are
132. 6:00normally metabolized the fastest in that
133. 6:03first instance
134. 6:05in what we will later know of as the
135. 6:08first Half-Life in this time right here
136. 6:12and right now let's jump back into
137. 6:15picturing the important aspects of
138. 6:17absorption