Ceftriaxone Pharmacokinetics Property - Essay Example

Ceftriaxone is classified as a third and fourth-generation cephalosporin. This spectrum of third and fourth-generation cephalosporins varies considerably and before administration, it is important to confirm based on culture and susceptibility testing before use. They are active against a broad range of gram-negative bacteria and moderately active against gram-positive bacteria. Ceftriaxone has a molecular weight of 661.59 with a chemical formula of C18H16N8Na2O7S3•3.5H2O. This formula has been illustrated below.

The drug is a white to yellowish powder in crystalline form that is readily soluble when put in water, and partly soluble in methanol and ethanol. Its PH of a 1 percent aqueous solution is 6.7. However, its color is bound to change depending on its length of storage, the concentration utilized as well as the diluent. It is provided in vials containing 10 grams of the drug to be reconstituted (Garot et al. 2011, p. 760).

The pharmacokinetic properties

The drug's average plasma concentration after administration following a 30 minutes intramuscular administration of 0.5 (350 mg/ml or 250mg/ml) or 1gram dosage and intravenous administration of 0.5, 1, and 2 grams dosages is illustrated in Table 1 below.

Table 1 axes are dosages against the average plasma concentration in time after administration.

0.5 hr

1 hr

2 hr

4 hr

6 hr

8 hr

12 hr

16 hr

24 hr

0.5 g IV

82

59

48

37

29

23

15

10

5

0.5 g IM (250 mg/ml)

22

33

38

35

30

26

16

ND

5

0.5 g IM (350 mg/ml)

20

32

38

34

31

24

16

ND

5

1 g IV

151

111

88

67

53

43

28

18

9

1 g IM

40

68

76

68

56

44

29

ND

ND

2 g IV

257

192

154

117

89

74

46

31

15

IV and IM ceftriaxone drug administration at a constant rate for 30 minutes since the administration

From the illustration, it is clear that the drug is completely absorbed following intramuscular administration. The mean maximum concentration of the drug occurs between 2 to 3 hours after the drug administration. Thus following an intramuscular administration, it is completely absorbed with a T max of 2-3 hours (Blumer 1991, p. 52).

The concentration of the drug in urine after administration

Table 2- Axis is dosage against the average urinary concentration

0-2 hrs

2-4 hrs

4-8 hrs

8-12 hrs

12-24 hrs

24-48 hrs

0.5 g IV

526

366

142

87

70

15

0.5 g IM

115

425

308

127

96

28

1g IV

995

855

293

147

132

32

1g IM

504

628

418

237

ND

ND

2g IV

2692

1976

757

274

198

40

It is distributed in most of the fluids in the body i.e. bones, kidneys, biliary tract, joints, and lungs. 33 to 67 percent of the drug is execrated in urine as an unchanged while the rest is secreted in the bile and found in feces as inactive drug compounds. The drug elimination half-life over a 0.15 to 3 g dosage ranges from 5.8 to 8.7 hours. The drug's apparent volume of distribution ranges from 5.78 to 13.5 L, with a plasma clearance of 0.58 to 1.45 L/hr and renal clearance of 0.32 to 0.73 L/hr. The drug is 85 percent to 95 percent protein bound. Moreover, it is reversibly bound to the plasma proteins and can cross the blood-placenta barrier (Joynt et al. 2001, par 1). However, the extent of its binding to proteins in the middle year is unknown.

Table 3- Illustrating the Average pharmacokinetics properties of ceftriaxone among different subjects

Group

Elimination half-life

The volume of distribution (L)

Plasma clearance (L/hr)

Healthy adult

5.8 to 8.7

5.8 to 13.5

0.58 to 1.45

Elderly persons

8.9

10.7

0.83

Renal impairment patients

Hemodialysis patients

14.7

13.7

0.65

Severe renal impairment

15.7

12.5

0.56

Moderate renal impairment

11.4

11.8

0.72

Mild impairment

12.4

13.3

0.70

Liver disease patients

8.8

13.6

1.1

From the comparison to a healthy adult, the pharmacokinetics of the drug is minimally altered among elderly individuals well in patients with hepatic dysfunction. Thus, no dosage adjustment was required among the group of patients. The drug was not removed to any significant extent from the body by hemodialysis (Patel et al. 1981, p. 639).

Drug indication and contraindication

The drug has been indicated for a variety of conditions due to its ability to cross the blood-placenta barrier. This includes treatment of acute otitis media, lower respiratory tract infections, pelvic inflammatory diseases, meningitis, and septicemia and for preoperative prophylaxis. Contraindications of the drug include concomitant use with calcium-containing solutions such as parenteral nutrition, among hyperbilirubinemia neonates and hypersensitivity to corn products (Yuk et al. 1989, par 1).

Conclusion

Ceftriaxone exhibits an exceptionally long half-life of 5.8 to 8.7 hours with a small degree of non-linearity that can be ignored in its clinical administration. After administration, 33 to 67 percent of the drug dosage is execrated in urine unchanged while the remainder is secreted in bile and feces. Following intramuscular administration, it is rapidly absorbed. It is distributed in most of the fluids in the body i.e. bones, kidneys, biliary tract, joints, and lungs. It has the ability to cross the blood-placenta barrier thus used in the treatment of meningitis and other conditions since it can penetrate the meninges. There are small changes in the pharmacokinetics properties of ceftriaxone among elderly persons and patients with renal dysfunction and dose adjustment is not required. Upon hemodialysis, the drug is not removed to a significant extent. However, it is important to monitor the plasma concentration of the drug to determine if any dosage adjustment is necessary.