| Zero-order | First-order | |
| Amount of drug eliminated per unit time | Constant amount | Constant fraction (Mnemonic: first = fraction) |
| Rate of elimination with plasma concentration | Independent | Directly proportional (greater the drug, greater is elimination) |
| Elimination | Capacity-limited, i.e. liver/kidney are saturated/maxed out on how much they can eliminate | Flow-limited, i.e. liver/kidney are not saturated on how much they can eliminate; drug is the rate limiting factor (Mnemonic: first = flow-limited) |
| t1/2 | Variable (not fixed) | Fixed or constant (Mnemonic: first = fixed) |
| Clearance (CL) | Variable | Fixed or constant (Mnemonic: first = fixed) |
| Serum drug concentration (Cp) vs time graph | Straight line | Curved line |
| Drugs | Mnemonic: Zero WATT Power | Most of the drugs |
| 1. Warfarin 2. Alcohol 3. Theophylline 4. Tolbutamide 5. Phenytoin |