Methods for determination of nontcas

There is no reliable spot test for commonly used non-TCAs. Also, currently there are no widely used immunoassays for non-TCAs. Chromatography techniques are most common, and well-established techniques are available for measurements as either a single drug or a group. Most of these antidepressants are well detected during comprehensive drug screening performed by using GC or HPLC.

Like TCAs, GC is widely used for screening and quantitation of non-TCAs. The methods involve either liquid-liquid or solid-phase extraction. Single-step extractions are generally successful, but methods describing multiple extractions or back-extractions have also been described. The method may involve assay of single drug or multiple drugs. A GC-MS method, involving acid hydrolysis, for simultaneous determination of citalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline in human urine samples has been described (44). A capillary GC-MS method, using selected ion

Table 2

Pharmacokinetic Properties of Other (Nontricyclic) Antidepressants

Table 2

Pharmacokinetic Properties of Other (Nontricyclic) Antidepressants

Active

Average

Vd

Oral

Average

Therapeutic

Toxic Level

Drug

Metabolite

Half-Life

(L/kg)

Bioavailability

Protein

Range

(ng/mL)

(hours)

Binding

(ng/mL)

Amoxapine

8 -hydroxy amoxapine

10

1

90

90

200^100b

>600b

Bupropion

Hydroxybupropiona

15

45

90

85

25-100

>400

Citalopram

Norcitalopram3

30

14

80

50

40-100

>250

Fluoxetine

Norlluoxetine

60

50

100

94

300-1000b

>2000b

Fluvoxamine

NA

23

25

95

77

20^100

Not known

Maprotiline

NA

33

24

100

88

150-300

>1000

Mirtazapine

Normirtazapine

30

12

90

85

4^10

Not known

Paroxetine

NA

22

15

90

95

20-200

>800

Sertraline

Norsertraline3

28

20

90

98

30-200

>500

Trazodone

NA

9

1

80

90

800-1600

>5000

Venlafaxine

o-Desmethyl venlafaxine

5

7

90

27

250-500b

>1000

Vd = Volume of distribution. NA, no significantly active metabolite. a Significantly less active than parent drug. b Total concentration of parent and active metabolite.

Vd = Volume of distribution. NA, no significantly active metabolite. a Significantly less active than parent drug. b Total concentration of parent and active metabolite.

monitoring, for the simultaneous determination of five antidepressant drugs fluoxetine, fluvoxamine, citalopram, sertraline, and paroxetine has been published (45).

Owing to heat labiality, certain antidepressants such as trazodone and nefazodone are not suitable for measurement using GC but can be easily analyzed using HPLC. HPLC is a commonly used method for determination of non-TCAs (46-49). An HPLC method for the simultaneous determination of citalopram, fluoxetine, paroxetine, and their metabolites has been described (48). The method involves solid-phase extraction and reversed-phase HPLC with fluorescence and UV detection. The limits of quantitation were 0.025 ^g/L for citalopram and paroxetine, and 0.10 ^g/L for fluoxetine and nor-fluoxetine, respectively. Another reversed-phase HPLC method for simultaneous determination of bicyclic, tricyclic and tetracyclic, and their metabolites is available (49).

When non-TCAs are measured using chromatographic techniques, their assays are relatively free from interferences.

Anxiety and Depression 101

Anxiety and Depression 101

Everything you ever wanted to know about. We have been discussing depression and anxiety and how different information that is out on the market only seems to target one particular cure for these two common conditions that seem to walk hand in hand.

Get My Free Ebook


Post a comment