Oral antimicrobial medication pharmacokinetics in turkey

Oral Antimicrobial Medication
Pharmacokinetics in Turkeys
by
DGS Burch BVetmed MRCVS
Octagon Services Ltd Copyright © November 2002
On-line at: www.octagon-services.co.uk

Notes to assist use of this spreadsheet:
These data give an overall pattern for an antimicrobial, obviously each reference or study has been carried out in a different way so the results may vary between studies.
1. Dose rate is usually given by gavage as a bolus dose in classical pharmacokinetic studies but for practical use in water and in feed studies are described. Estimated dose rates have an 'e' denoting them for comparative use.
2. Cmax is the peak level found in serum after administration and is the highest level that can be achieved with a certain antimicrobial at a certain dose.
Administration by water and feed usually gives a much lower figure because the drug is given over a 24-hour period and feed slows the passage and sometimes affects the absorption of some compounds.
3. C 12hours is the level of antimicrobial found in the blood 12 hours after administration. Products with a fast clearance usually have gone by 12 hours. When given in feed levels may be lower but can persist for longer periods.
4. Steady state is the level achieved during water or feed medication and the average level that is achieved over a 24 hour period.This is the most important level for many antimicrobials as they act by inhibiting the growth of the bacteria and require a prolonged exposure. Concentrations in other target tissues like lung or gut contents are also important when dealing with infections in those areas as well as eggs, to prevent vertical transmission.
5. Protein binding of an antimicrobial is important as it can affect the effective concentration of that particular antimicrobial against an organism. High binding (over 70%) is therefore not usually good.
6. Bioavailability is the comparison of the absorption of a product from the gut in comparison with a dose given intravenously (assumed 100%). It is important if you want an antimicrobial to go from the gut to a target in the body. A high bioavailability means a drug is likely to work systemically although other factors can affect this. Feed may interfere with the absorption and bioavailability of a product.
7. Lung concentration is important if you want to treat an infection in the lung. Some antibiotics specifically concentrate in lung tissue and air sacs.
8. Egg concentration is important to treat or prevent the vertical transmission of many mycoplasma infections.

Overall, understanding the pharmacokinetics of an antimicrobial, knowing its level at the site of infection and the Minimal Inhibitory Concentration (MIC) of an organism to treat, can help the veterinarian to decide on what product, what dose, how it should be administered, for how long and improve the therapeutic control of the disease and thereby reduce the chances of developing antimicrobial resistance.

Pharmacokinetics graph for antimicrobials medication

The data in the following table are provided free and without obligation, for demonstration purposes - readers should seek expert guidance before taking decisions requiring critical product specifications.

Antibiotic	Reference	Dose rate mg/kg	Water Conc. ppm	C max µg/ml	C12hrs µg/ml	Steady state µg/ml	Bio- avail. %	Lung conc. µg/g	Egg conc. µg/g

Tiamulin	Laber & Schutze, 1979	25		1.1	<0.1
		50		3	0.4
Tiamulin	Horrox et al, 1980	16e	250 (breeders)			0.36 (range 0.2-0.5)			Max 3.7-4.4

Tylosin	Laber & Schutze, 1979	50		0.9	0.3

Chlortetracycline	Pollet et al, 1984	10		1.05	0.2
		15		1.1	0.3
		20		1.6	0.5
Chlortetracycline	Ziv et al, 1997		200			0.14
			400			0.24
			800			0.39
			1600			0.57
			2500			0.81

Oxytetracycline	Ziv et al, 1997		200			0.2
			400			0.35
			800			0.55
			1600			0.82
			2500			1.15

Doxycycline	Santos et al, 1997a		250	4.9-5.7	C min 0.7
			750	12.5	C min 2.7
		25mg	water	1.7	C min 0.5
				Fed/Fast			Fed/Fast
Doxycycline	Santos et al, 1997b	25	3 day old	2.5/3.8
			3 week old	6.1/5.6
			6 week old	4.8/7.4
			12 wk old	3.0/5.7			40/84

Enrofloxacin	Product data		50	0.6		0.5		1.2
	ref www.poultry.baytril.com
Enrofloxacin	Heinen et al, 1997		50			0.29		0.7
Enrofloxacin	Heinen & Pirro, 2000	10		0.87	0.27			Max 1.97
Enrofloxacin	Delaporte et al, 1994	5							Max 2.58
		10							Max 4.33

Difloxacin	Heinen & Pirro, 2000	10		0.71	0.04			Max 0.85

Sarafloxacin	Heinen et al, 1997		50			<0.015		<0.03

Norfloxacin	Gulkarov & Ziv, 1994	40	200	0.88		0.48	40	0.56
nicotinate			(144 norflox)
Antibiotic	Reference	Dose rate mg/kg	Water Conc. ppm	C max µg/ml	C12hrs µg/ml	Steady state µg/ml	Bio- avail. %	Lung conc. µg/g	Egg conc. µg/g

Poultry technical papers on-line here: Index
Oral Antimicrobial Pharmacokinetics: Chickens Pigs

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Poultry technical papers on-line here: Index Oral Antimicrobial Pharmacokinetics: Chickens Pigs

Poultry technical papers on-line here: Index
Oral Antimicrobial Pharmacokinetics: Chickens Pigs