Withdrawal period is the minimum time that must pass before meat, milk, or eggs from treated animals can be released for human consumption. This period ensures that drug residues fall below the Maximum Residue Limit (MRL). This article reviews the concept of withdrawal periods, calculation principles, common drug groups, and the importance of food safety under current regulations.
Legal Warning
Failing to respect the withdrawal period creates a food safety violation and may lead to serious legal penalties. It also contributes to antimicrobial resistance. Always follow your veterinarian's advice and the product leaflet.
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Calculate the safe date for slaughter or milk sale from the drug administration date.
Calculate Withdrawal Period1. What Is a Withdrawal Period?
The withdrawal period is the time required after drug administration for residues in animal products to fall to acceptable levels. It depends on the drug's pharmacokinetic properties (absorption, distribution, metabolism, and excretion) (EMEA, 2000).
The time that must pass after drug administration before milk can be sold or used for human consumption.
- Usually expressed in hours or number of milkings
- Longer for intramammary drugs
- Variable for systemic drugs
The time that must pass after drug administration before the animal can be sent for slaughter.
- Usually expressed in days
- Higher residues in injection sites
- Accumulation may occur in liver and kidney
2. Maximum Residue Limit (MRL)
2.1 What Is MRL?
MRL (Maximum Residue Limit) is the maximum amount of drug residue allowed in animal-derived food. MRL values are legally defined in the EU and Türkiye (EC 37/2010).
| Tissue/Product | Why Important | Example MRL (Oxytetracycline) |
|---|---|---|
| Muscle (meat) | Most consumed tissue | 100 µg/kg |
| Liver | Metabolic organ, high accumulation | 300 µg/kg |
| Kidney | Excretion organ, high accumulation | 600 µg/kg |
| Fat | Lipophilic drugs accumulate | 100 µg/kg |
| Milk | Consumed daily, children are sensitive | 100 µg/kg |
2.2 How MRL Is Determined
MRL values are established through comprehensive toxicological studies:
- ADI (Acceptable Daily Intake): the acceptable daily intake
- Safety factor: usually a 100-1000-fold margin
- Consumption amount: average daily food intake
3. Common Drug Groups and Withdrawal Periods
3.1 Antibiotics
| Drug Group | Example Drugs | Meat Withdrawal (days) | Milk Withdrawal (hours/milkings) |
|---|---|---|---|
| Penicillins | Amoxicillin, Ampicillin | 7-21 | 48-96 h (4-8 milkings) |
| Tetracyclines | Oxytetracycline, Doxycycline | 14-28 | 72-144 h |
| Macrolides | Tylosin, Erythromycin | 14-28 | 72-96 h |
| Aminoglycosides | Gentamicin, Streptomycin | 30-60 | 72-96 h |
| Fluoroquinolones | Enrofloxacin, Marbofloxacin | 7-14 | Not used in dairy cows |
| Sulfonamides | Sulfadiazine, Sulfamethoxazole | 10-21 | 72-96 h |
Important Note
The above times are general reference values. Always follow the withdrawal period stated in the product leaflet. The same active ingredient may have different withdrawal periods in different formulations.
3.2 Antiparasitic Drugs
| Drug Group | Example Drugs | Meat Withdrawal (days) | Milk Withdrawal |
|---|---|---|---|
| Ivermectins | Ivermectin, Doramectin | 28-49 | Not used in dairy cows |
| Benzimidazoles | Albendazole, Fenbendazole | 14-28 | 72-120 h |
| Levamisole | Levamisole HCl | 7-14 | 72 h |
| Coccidiostats | Amprolium, Toltrazuril | 0-7 | 0-24 h |
3.3 Anti-inflammatory Drugs (NSAIDs)
| Drug | Meat Withdrawal (days) | Milk Withdrawal (hours) |
|---|---|---|
| Meloxicam | 15 | 120 h (5 days) |
| Flunixin meglumine | 4-10 | 36-48 h |
| Ketoprofen | 1-4 | 0-24 h |
| Carprofen | 21 | 0 h (in some countries) |
4. Factors Affecting the Withdrawal Period
Drug-Related Factors
- Formulation: long-acting (LA) > short-acting
- Route: IM > SC > IV > oral
- Dose: higher dose = longer withdrawal
- Half-life: longer t½ = longer withdrawal
- Lipophilicity: fat-soluble drugs accumulate in adipose tissue
Animal-Related Factors
- Species: metabolic rates differ
- Age: metabolism is slower in young animals
- Health status: liver/kidney disease
- Body condition: more accumulation in fat animals
- Lactation: excretion via milk
5. Intramammary Antibiotics
Intramammary antibiotics used for mastitis treatment are especially important in terms of milk withdrawal time.
| Product Type | Use | Milk Withdrawal | Meat Withdrawal |
|---|---|---|---|
| Lactation products | Treatment of clinical mastitis | 48-144 h (4-12 milkings) | 7-28 days |
| Dry-cow products | Protection at dry-off | Whole dry period + 72-96 h | 28-60 days |
Dry-Cow Products
Dry-cow antibiotics are formulated assuming a minimum 60-day dry period. If calving occurs early or the dry period is short, the withdrawal period may be longer. Milk after calving must always be tested.
6. Withdrawal Calculation
Calculating the Safe Slaughter/Sales Date
Safe Date = Drug Administration Date + Withdrawal PeriodExample: An antibiotic with a 21-day meat withdrawal was given on January 15.
Safe slaughter date = January 15 + 21 days = February 5
6.1 Multiple Drug Use
When more than one drug is used, the longest withdrawal period should be used:
Example scenario:
- January 1: Antibiotic A (14-day withdrawal) → Safe: January 15
- January 5: Antibiotic B (21-day withdrawal) → Safe: January 26
- January 10: NSAID (4-day withdrawal) → Safe: January 14
- Result: Latest safe date = January 26
7. Residue Testing and Control
7.1 Rapid Tests
Rapid tests can be used to detect antibiotic residues in milk:
- Delvotest: broad spectrum, result in 2.5-3 h
- Beta-Star: for beta-lactams, 5 min
- Charm Test: multi-antibiotic, 8 min
- SNAP Test: rapid screening, 10 min
7.2 Official Controls
In Türkiye, residue control in animal-derived food is carried out by the Ministry of Agriculture and Forestry. Regular samples are collected at slaughterhouses and milk collection centers.
8. Record Keeping
Drug use records are a legal requirement and must be kept for at least 5 years:
- Animal identification (ear tag number)
- Drug name and active ingredient
- Administration date and dose
- Route of administration
- Withdrawal period and safe date
- Prescribing veterinarian
9. Sources
- EMEA. (2000). Note for guidance on the risk analysis approach for residues of veterinary medicinal products in food of animal origin. EMEA/CVMP/187/00.
- European Commission. (2010). Commission Regulation (EU) No 37/2010 on pharmacologically active substances and their classification regarding maximum residue limits in foodstuffs of animal origin.
- Tarım ve Orman Bakanlığı. (2022). Veteriner Tıbbi Ürünler Yönetmeliği.
- Riviere, J. E., & Papich, M. G. (2018). Veterinary Pharmacology and Therapeutics (10th ed.). Wiley-Blackwell.