Drug Half Life Calculator

Drug Half
Life Calculator

Easily find out how long do drugs stay in your system. Enter a drug and dose, or see a demo.

Drug
Dose
Half-life
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Your Best Half Life Calculator

Finally, a modern yet simple multiple drug half life calculator that is flexible enough to suit all your needs.
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Skip unneeded research with half life suggestions. Just enter the drug and dose and get your results in seconds.
Combine drugs and doses
Add multiple ingestions for the same or different drugs. See how they accumulate and find the optimal dose.
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Accurately determine how much drug is in your body after a certain time on a full-screen drug half life chart. Easily save or share it!
Learn what does half life of a drug mean and how it can help you plan your medication doses and frequency.

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How to use the drug calculator?

This drug concentration calculator is an easy tool to determine the amount of substance left in your system. It does so by looking at the elimination half life of a medication.

Use it to keep constant levels of medicine in the body, or avoid unwanted interactions between substances.

Try a demo to get an idea of how it works. Or enter your data as follows:

  • Drug - drug name on the graph. It can be anything, but half life for common drugs is auto-filled.
  • Dose - amount of the drug taken.
  • Half life - half life of medicine. Select a drug from the list of suggestions to fill it out automatically.
  • Offset (optional) - how long after the initial administration you took another dose.

You can add unlimited ingestions to track multiple drugs or repeating doses of the same one.

Once you enter the required data for at least one ingestion, the graph shows the results:

  • Time - how much time has passed since you've first taken the drug.
  • Residuals - how much drug is left in your body.

Hover on the graph to get a precise amount of drug left at any time.

You can consider the drug eliminated when about 97% of it is gone. That's when most drugs no longer have any effect.

What is half life of a drug?

A drug's half life is an estimate of time it takes the amount of drug in the body to reduce by half. Now that you know the drug half life definition, let's continue to the exciting stuff!

If you took 200 mg of a drug with a half life of 1 hour:

  • 100mg remains after 1 hours
  • 50mg remains after 2 hours
  • 25mg remains after 3 hours
  • 12.5mg remains after 4 hours
  • 6.25mg remains after 5 hours

Almost 97% of the drug is eliminated after 5 hours. This is usually enough to consider the drug's effects negligible.

How many half lives to eliminate a drug?

As seen above, eliminating a drug takes 4 to 5 half lives. Note that drug tests can detect the usage longer.

Doubling the dose increases the time to eliminate it by one half life.

After learning what does half life of a drug mean, let's look at how to use it.

Why is half life of a drug important?

Half life helps you evaluate how often to take the drug to maximize effects and minimize adverse reactions. You can maintain a minimum effective level of drug in the body by adjusting your doses or their frequency.

This is irreplaceable knowledge for tapering, titrating, or reaching a steady state.

When tapering, you gradually decrease the dose of medication to stop using it. Decrease it too quickly, and you experience withdrawals. But decrease it too slowly, and you suffer side effects unnecessarily long.

Titration increases the dose for maximum benefit without side effects.

The drug needs to remain at a constant level (be in a steady state) during treatment to produce the desired effect. It happens when you consume the same amount of drug that's eliminated from the body.

For all of the above, knowing how much of the drug is left in your body and how it compounds is necessary. With this knowledge, you quickly establish a dose and administration schedule.

You can also use the drug elimination calculator to simulate loading doses, as some drugs need weeks of taking to reach optimal levels in your body.

And last but not least, you can limit drug interactions, as you know how much drug is left in the body at the time of the second administration. This helps preserve drug efficacy and avoid unwanted side effects.

How to calculate half life of a drug?

We use the following half-life of drug formula to calculate medication half life:

Learn how to calculate half life of a drug with this medication half life calculator.
  • x - time on the graph.
  • y - remaining amount of the drug at time x.
  • dose - initial amount of the drug.
  • offset - time since the first administration.
  • halfLife - half life of medication (the time it takes to eliminate half of the drug).

The formula assumes exponential decay. The substance decreases by half over each interval, which equals its half-life. If the time is less than the offset, the remaining amount is considered 0.

But don't worry about the math, as calculating half life is simple with this drug accumulation calculator.

Half lives of common drugs

Here's a list of common drugs and their half lives. The half life is auto-filled when you select any of these drugs. You can adjust it if needed.

Drug Average Estimated range
Abilify 4 days 96 h
Acebutolol 3.5 h 3 - 4 h
Acetaminophen 2.5 h 1 - 4 h
Acetylcysteine 5.5 h 5 - 6 h
Acyclovir 2.5 h 2 - 3 h
Adderall 20.5 h 7 - 34 h
Adinazolam 3 h 3 h
Adrenaline 2.5 min 2 - 3 min
Advil 1.75 h 1.5 - 2 h
Alcohol 4.5 h 4 - 5 h
Aleve 12 h 12 h
Alprazolam 15 h 10 - 20 h
Alprostadil 5 min 5 min
Amantadine 30 h 20 - 40 h
Ambien 2.5 h 2 - 3 h
Amfepramone 5 h 4 - 6 h
Amikacin 2.5 h 2 - 3 h
Amineptine 2.5 h 2.5 h
Amiodarone 66.5 days 26 - 107 days
Amisulpride 12 h 12 h
Amitriptyline 29.5 h 8 - 51 h
Amlodipine 40 h 30 - 50 h
Amoxapine 24 h 24 h
Amoxicillin 1.5 h 1 - 2 h
Amphetamine 20.5 h 7 - 34 h
Amphotericin 15 days 15 days
Amprenavir 9 h 7 - 11 h
Anafranil 3 days 72 h
Anidulafungin 45 h 40 - 50 h
Apomorphine 45 min 30 - 60 min
Argatroban 45 min 39 - 51 min
Aripiprazole 4 days 96 h
Asendin 24 h 24 h
Aspirin 6 h 3 - 9 h
Atenolol 6.5 h 6 - 7 h
Ativan 15 h 10 - 20 h
Atomoxetine 5 h 5 h
Atorvastatin 14 h 14 h
Azilect 3 h 3 h
Azithromycin 2.8 days 68 h
Aztreonam 1.5 h 1 - 2 h
Baclofen 3 h 2 - 4 h
Benadryl 12 h 12 h
Bentazepam 3 h 2 - 4 h
Betamethasone 45 h 36 - 54 h
Bethanechol 30 min 30 min
Bismuth 46.5 days 21 - 72 days
Bretazenil 2.5 h 2.5 h
Bromazepam 30 h 20 - 40 h
Bromocriptine 24 h 24 h
Brotizolam 4.5 h 4 - 5 h
Buprenorphine 45 h 20 - 70 h
Bupropion 21 h 12 - 30 h
BuSpar 2.5 h 2 - 3 h
Buspirone 2.5 h 2 - 3 h
Butalbital 35 h 35 h
Cabergoline 3 days 72 h
Caffeine 7.5 h 3 - 12 h
Camazepam 17.5 h 6 - 29 h
Cannabidiol 25 h 18 - 32 h
Cannabis 30.3 h 1.6 - 59 h
Capreomycin 12 h 12 h
Carbamazepine 30.5 h 14 - 47 h
Cardizem 3.75 h 3 - 4.5 h
Carfentanil 8 h 8 h
Carisoprodol 2 h 1 - 3 h
Carvedilol 8.5 h 7 - 10 h
Caspofungin 10 h 9 - 11 h
CBD 25 h 18 - 32 h
Cefuroxime 1.5 h 1 - 2 h
Celexa 35 h 35 h
Cephalexin 1 h 1 h
Cetirizine 8 h 8 h
Chlordiazepoxide 17.5 h 5 - 30 h
Chlorpheniramine 24 h 21 - 27 h
Chlorpromazine 30 h 30 h
Chlorprothixene 10 h 8 - 12 h
Chlorzoxazone 1 h 1 h
Cialis 17.5 h 17.5 h
Cinazepam 60 h 60 h
Cinolazepam 9 h 9 h
Ciprofloxacin 4 h 4 h
Citalopram 35 h 35 h
Clarithromycin 3.5 h 3 - 4 h
Claritin 8 h 8 h
Clindamycin 3 h 2 - 4 h
Clobazam 34 h 8 - 60 h
Clobenzorex 12 h 10 - 14 h
Clomipramine 3 days 72 h
Clonazepam 39.5 h 19 - 60 h
Clonazolam 14 h 10 - 18 h
Clonidine 14 h 12 - 16 h
Clorazepate 2 days 48 h
Clotiazepam 4 h 4 h
Clotrimazole 2 h 2 h
Cloxazolam 3.8 days 80 - 105 h
Clozapine 35 h 4 - 66 h
Clozaril 35 h 4 - 66 h
Cocaine 1 h 1 h
Codeine 3 h 3 h
Compazine 5 h 4 - 8 h
Coumadin 40 h 40 h
Cyclobenzaprine 22.5 h 8 - 37 h
Cycloserine 12 h 12 h
Cyclosporine 16.5 h 6 - 27 h
Cylert 12 h 12 h
Cymbalta 12 h 12 h
Cyproheptadine 8.5 h 8 - 9 h
Dapoxetine 1.5 h 1.5 h
Darvocet 33 h 30 - 36 h
Delavirdine 6.5 h 2 - 11 h
Delorazepam 3.8 days 80 - 105 h
Depacon 12.5 h 9 - 16 h
Depakene 12.5 h 9 - 16 h
Depakote 12.5 h 9 - 16 h
Depixol 35 h 35 h
Desipramine 33 h 12 - 54 h
Desoxyn 20 h 10 - 30 h
Desvenlafaxine 11 h 10 - 13 h
Desyrel 8.5 h 7 - 10 h
Dexamethasone 3 h 3 h
Dexbrompheniramine 25 h 25 h
Dexedrine 10 h 9 - 11 h
Dextroamphetamine 10 h 9 - 11 h
Dextromethorphan 3 h 2 - 4 h
Diamorphine 4 min 2 - 6 min
Diazepam 39.5 h 32 - 47 h
Diclofenac 1.5 h 1 - 2 h
Dicloxacillin 42 min 42 min
Dicyclomine 3.5 h 2 - 5 h
Diethylpropion 5 h 4 - 6 h
Diflunisal 10 h 8 - 12 h
Digitoxin 7 days 4 - 10 days
Digoxin 42 h 36 - 48 h
Dihydrocodeine 4 h 4 h
Dilaudid 2.5 h 2 - 3 h
Diltiazem 3.75 h 3 - 4.5 h
Diphenhydramine 12 h 12 h
Disopyramide 7 h 4 - 10 h
Divalproex 12.5 h 9 - 16 h
DMT 15 min 15 min
Donepezil 75 h 50 - 100 h
Dostinex 3 days 72 h
Dosulepin 29.5 h 14 - 45 h
Doxepin 16.5 h 8 - 25 h
Doxycycline 20 h 18 - 22 h
Droperidol 2 h 2 h
Duloxetine 12 h 12 h
Duragesic 22 h 17 - 27 h
Dutasteride 31.5 days 28 - 35 days
Efavirenz 47.5 h 40 - 55 h
Effexor 11 h 9 - 13 h
Elavil 29.5 h 8 - 51 h
Eldepryl 10 h 10 h
Emsam 21.5 h 18 - 25 h
Ephedrine 4.5 h 3 - 6 h
Erenumab 28 days 28 days
Escitalopram 29.5 h 27 - 32 h
Esomeprazole 1.5 h 1 - 2 h
Estazolam 20.5 h 10 - 31 h
Eszopiclone 6 h 6 h
Ethambutol 24 h 24 h
Ethosuximide 2.3 days 50 - 60 h
Ethyl 4 days 73 - 119 h
Etizolam 6 h 6 h
Etoricoxib 22 h 22 h
Everolimus 32 h 26 - 38 h
Felbamate 17 h 11 - 23 h
Fentanyl 7.5 h 3 - 12 h
Flecainide 19.5 h 12 - 27 h
Flomax 7 h 5 - 9 h
Flubromazepam 6.7 days 100 - 220 h
Fluconazole 35 h 20 - 50 h
Flucytosine 4 h 3 - 5 h
Flumazenil 1 h 40 - 80 min
Flunitrazepam 22 h 18 - 26 h
Fluoxetine 5 days 4 - 6 days
Flupenthixol 35 h 35 h
Fluphenazine 8.5 days 7 - 10 days
Flurazepam 6 days 40 - 250 h
Flutazolam 3.5 h 3.5 h
Flutoprazepam 75 h 60 - 90 h
Fluvoxamine 12.5 h 12 - 13 h
Fondaparinux 19 h 17 - 21 h
Gabapentin 6 h 5 - 7 h
Gabitril 6.5 h 5 - 8 h
Ganciclovir 4.5 h 3 - 6 h
Gentamicin 2 h 1 - 3 h
Geodon 7 h 7 h
Halazepam 2.7 days 30 - 100 h
Halcion 3.5 h 1.5 - 5.5 h
Haldol 27.5 h 14 - 41 h
Haloperidol 25.5 h 14 - 37 h
HCTZ 22 h 6 - 15 h
Heparin 4.5 h 3 - 6 h
Heroin 4 h 1 - 7 h
Hydrochlorothiazide 10.5 h 6 - 15 h
Hydrocodone 5 h 4 - 6 h
Hydromorphone 2.5 h 2 - 3 h
Hydroxychloroquine 50 days 1 - 2 mos
Hydroxyzine 22 h 20 - 24 h
Ibuprofen 2 h 1 - 3 h
Imipramine 13 h 6 - 20 h
Imovane 5.5 h 5 - 6 h
Inapsine 2 h 2 h
Indinavir 2 h 1 - 3 h
Indomethacin 7.5 h 3 - 12 h
Invega 1 day 23 h
Isoniazid 1.5 h 1 - 2 h
Itraconazole 16 h 14 - 18 h
Ketamine 1.5 h 1 - 2 h
Ketazolam 2.7 days 30 - 100 h
Ketoconazole 5 h 2 - 8 h
Klonopin 39.5 h 19 - 60 h
Lacosamide 13 h 13 h
Lamictal 22.5 h 15 - 30 h
Lamotrigine 22.5 h 15 - 30 h
Lansoprazole 1.5 h 1.5 h
Leflunomide 16 days 14 - 18 days
Levetiracetam 7 h 6 - 8 h
Levitra 4.5 h 4 - 5 h
Levocetirizine 8 h 6 - 10 h
Levofloxacin 7 h 6 - 8 h
Levorphanol 13.5 h 11 - 16 h
Levothyroxine 6.5 days 3 - 10 days
Lexapro 29.5 h 27 - 32 h
Librium 17.5 h 5 - 30 h
Lidocaine 1.5 h 1 - 2 h
Lipitor 14 h 14 h
Lisdexamfetamine 10 h 9 - 11 h
Lisinopril 12 h 12 h
Lithium 22 h 14 - 30 h
Loperamide 11.5 h 9 - 14 h
Lopinavir 5 h 4 - 6 h
Loprazolam 9 h 6 - 12 h
Lopressor 5 h 3 - 7 h
Loratadine 8 h 8 h
Lorazepam 15 h 10 - 20 h
Lormetazepam 11 h 10 - 12 h
Lortab 5 h 4 - 6 h
Losartan 2 h 2 h
Loxapine 6 h 4 - 8 h
LSD 4 h 3 - 5 h
Ludiomil 3 days 36 - 105 h
Lupron 3 h 3 h
Luvox 12.5 h 12 - 13 h
Lyrica 6.3 h 6.3 h
Manerix 1.5 h 1 - 2 h
Maprotiline 3 days 36 - 105 h
MDMA 6 h 4 - 8 h
Medazepam 5 days 36 - 200 h
Melatonin 42.5 min 35 - 50 min
Meloxicam 20 h 20 h
Meperidine 3.5 h 2 - 5 h
Mephobarbital 2 days 48 - 52 h
Meprobamate 11.5 h 6 - 17 h
Mesoridazine 1.5 days 24 - 48 h
Metformin 6.5 h 4 - 9 h
Methadone 37.5 h 15 - 60 h
Methamphetamine 17.5 h 5 - 30 h
Methocarbamol 1.5 h 1 - 2 h
Methotrexate 6.5 h 3 - 10 h
Methylphenidate 3.5 h 2 - 5 h
Metoprolol 5 h 3 - 7 h
Metronidazole 8 h 8 h
Micardis 24 h 24 h
Midazolam 2 h 90 - 150 min
Milnacipran 8 h 8 h
Minocycline 18.5 h 12 - 25 h
Mirapex 10 h 8 - 12 h
Mirtazapine 30 h 20 - 40 h
Moclobemide 1.5 h 1 - 2 h
Modafinil 15 h 15 h
Molindone 1.5 h 90 min
Morphine 4 h 1 - 7 h
Muse 5 min 5 min
Mycophenolic 13 h 8 - 18 h
Naloxone 1.5 h 1.5 h
Naltrexone 13 h 13 h
Naproxen 18 h 12 - 24 h
Navane 15 h 10 - 20 h
Nefazodone 3 h 2 - 4 h
Nelfinavir 4.5 h 4 - 5 h
Neostigmine 1 h 50 - 90 min
Neurontin 6 h 5 - 7 h
Nevirapine 27.5 h 25 - 30 h
Nexium 1.5 h 1 - 2 h
Nicotine 1.5 h 1 - 2 h
Nimesulide 3.5 h 2 - 5 h
Nimetazepam 22 h 14 - 30 h
Nitrazepam 32.5 h 17 - 48 h
Nordiazepam 5 days 36 - 200 h
Norpramin 33 h 12 - 54 h
Nortriptyline 53 h 16 - 90 h
Nucynta 4 h 4 h
Ofloxacin 8.5 h 8 - 9 h
Olanzapine 37.5 h 21 - 54 h
Omeprazole 1 h 1 h
Ondansetron 5.7 h 5.7 h
Opana 8 h 7 - 9 h
Oxazepam 7.5 h 4 - 11 h
Oxcarbazepine 3 h 1 - 5 h
Oxycodone 4 h 3 - 5 h
OxyContin 4 h 3 - 5 h
Oxymorphone 8 h 7 - 9 h
Paliperidone 1 day 23 h
Pamelor 53 h 16 - 90 h
Pantoprazole 1.5 h 1 - 2 h
Parlodel 24 h 24 h
Parnate 2.5 h 2 - 3 h
Paroxetine 21 h 21 h
Paxil 21 h 21 h
Pemoline 12 h 12 h
Penicillin 28 h 30 min-56h
Pentazocine 3.6 h 1.5 - 10 h
Pentobarbital 31.5 h 15 - 48 h
Percocet 4 h 3 - 5 h
Pergolide 27 h 27 h
Periactin 8.5 h 8 - 9 h
Perphenazine 14 h 8 - 20 h
Pethidine 3.5 h 2 - 5 h
Phenazepam 2.5 days 60 h
Phendimetrazine 21.5 h 19 - 24 h
Phenelzine 12 h 12 h
Phenobarbital 4 days 81 - 117 h
Phentermine 25 h 25 h
Phenylephrine 3 h 2.5 - 3.5 h
Phenytoin 20 h 18 - 22 h
Pimozide 2.3 days 55 h
Pinazepam 3 days 40 - 100 h
Piribedil 4.2 h 1.7 - 6.7 h
Posaconazole 34.5 h 32 - 37 h
Pramipexole 10 h 8 - 12 h
Prazepam 5 days 36 - 200 h
Prednisone 27 h 18 - 36 h
Pregabalin 6.3 h 6.3 h
Premazepam 11.5 h 10 - 13 h
Prevacid 1.5 h 1 - 2 h
Prilosec 1.5 h 1 - 2 h
Primidone 5 h 3 - 7 h
Pristiq 11 h 10 - 13 h
Procainamide 3.5 h 2 - 5 h
Prochlorperazine 5 h 4 - 8 h
Prolixin 15 h 15 h
Promazine 6 h 6 h
Promethazine 17.5 h 16 - 19 h
Propafenone 6 h 2 - 10 h
Propoxyphene 33 h 30 - 36 h
Propranolol 4 h 2 - 6 h
Prostigmin 1 h 50 - 90 min
Protriptyline 3 days 54 - 92 h
Provigil 15 h 15 h
Prozac 5 days 4 - 6 days
Pseudoephedrine 6 h 4 - 8 h
Psilocybin 2.7 h 100 - 220 min
Pyrazinamide 9.5 h 9 - 10 h
Pyrazolam 17 h 16 - 18 h
Quazepam 79.5 h 39 - 120 h
Quetiapine 7 h 7 h
Quinidine 7 h 5 - 9 h
Rabeprazole 1.5 h 1.5 h
Ranexa 1.65 h 1.4 - 1.9 h
Ranitidine 2.5 h 2 - 3 h
Ranolazine 1.65 h 1.4 - 1.9 h
Rasagiline 3 h 3 h
Reboxetine 12 h 12 h
Remeron 30 h 20 - 40 h
Restoril 11.5 h 8 - 15 h
Requip 5.5 h 5 - 6 h
Rifabutin 42.5 h 16 - 69 h
Rifampin 2.5 h 2 - 3 h
Rilmazafone 10.5 h 10 - 11 h
Risperdal 20 h 20 h
Risperidone 20 h 20 h
Ritalin 3.5 h 2 - 5 h
Ritonavir 4 h 3 - 5 h
Rivaroxaban 7 h 5 - 9 h
Robitussin DM 4.5 h 3 - 6 h
Ropinirole 5.5 h 5 - 6 h
Roxicodone 4 h 3 - 5 h
S-Adenosyl 1.6 h 100 min
Salicylate 2.5 h 2 - 3 h
SAM-e 1.6 h 100 min
Saquinavir 12 h 9 - 15 h
Savella 8 h 8 h
Secobarbital 25.5 h 22 - 29 h
Selegiline 21.5 h 18 - 25 h
Seroquel 7 h 7 h
Sertindole 3 days 3 days
Sertraline 29 h 13 - 45 h
Serzone 3 h 2 - 4 h
Sibutramine 15 h 14 - 16 h
Sildenafil 3.5 h 3 - 4 h
Simvastatin 2.5 h 2 - 3 h
Sinequan 16.5 h 8 - 25 h
Sirolimus 2.6 days 46 - 78 h
Sodium 12.5 h 9 - 16 h
Solian 12 h 12 h
Soma 2 h 1 - 3 h
Sonata 75 min 60 - 90 min
Stablon 3 h 3 h
Stelazine 15 h 10 - 20 h
Strattera 5 h 5 h
Streptomycin 5.5 h 5 - 6 h
Suboxone 45 h 20 - 70 h
Subutex 45 h 20 - 70 h
Sufentanil 4.4 h 4.4 h
Sulfamethoxazole 10 h 10 h
Sulfasalazine 7.5 h 5 - 10 h
Sulpiride 7 h 6 - 8 h
Survector 2.5 h 2.5 h
Symbyax 5 days 4 - 6 days
Symmetrel 30 h 20 - 40 h
Synthroid 7 days 7 days
Tacrolimus 19.5 h 4 - 35 h
Tadalafil 17.5 h 17.5 h
Talwin 3.6 h 1.5 - 10 h
Tamsulosin 6 h 5 - 7 h
Tapentadol 4 h 4 h
Tegretol 30.5 h 14 - 47 h
Telmisartan 24 h 24 h
Temazepam 14 h 8 - 20 h
Tenuate 5 h 4 - 6 h
Tetracycline 9 h 7 - 11 h
Tetrahydrocannabinol 30.3 h 1.6 - 59 h
Tetrazepam 14.5 h 3 - 26 h
Theophylline 9 h 7 - 11 h
THC 30.3 h 1.6 - 59 h
Thienalprazolam 25 h 10 - 40 h
Thioridazine 22.5 h 21 - 24 h
Thiothixene 15 h 10 - 20 h
Thorazine 30 h 30 h
Tiagabine 6.5 h 5 - 8 h
Tianeptine 3 h 3 h
Tizanidine 2.5 h 2.5 h
Tobramycin 2 h 2 h
Tofranil 13 h 6 - 20 h
Topamax 22 h 19 - 25 h
Topiramate 22 h 19 - 25 h
Tramadol 7 h 6 - 8 h
Tranxene 2 days 48 h
Tranylcypromine 2.5 h 2 - 3 h
Trazodone 8.5 h 7 - 10 h
Triazolam 3.5 h 1.5 - 5.5 h
Trifluoperazine 15 h 10 - 20 h
Trilafon 14 h 8 - 20 h
Trileptal 3 h 1 - 5 h
Trimethoprim 10 h 8 - 12 h
Trimipramine 27.5 h 16 - 39 h
Surmontil 27.5 h 16 - 39 h
Truxal 10 h 8 - 12 h
Tylenol 2.5 h 1 - 4 h
Ultram 6.5 h 6 - 7 h
Uprima 45 min 30 - 60 min
Urecholine 30 min 30 min
Valium 39.5 h 32 - 47 h
Valproic 12.5 h 9 - 16 h
Vancomycin 7.5 h 4 - 11 h
Vardenafil 4.5 h 4 - 5 h
Venlafaxine 11 h 9 - 13 h
Viagra 3.5 h 3 - 4 h
Vibramycin 20 h 18 - 22 h
Vicodin 5 h 4 - 6 h
Vivactil 3 days 54 - 92 h
Voltaren 1.5 h 1 - 2 h
Voriconazole 7.5 h 6 - 9 h
Vyvanse 10 h 9 - 11 h
Warfarin 40 h 20 - 60 h
Weed 30.3 h 1.6 - 59 h
Wellbutrin 21 h 12 - 30 h
Xanax 15 h 10 - 20 h
Xarelto 7 h 5 - 9 h
Yohimbine 1.4 h 15 - 150 min
Zaleplon 75 min 60 - 90 min
Ziprasidone 7 h 7 h
Zocor 2 h 2 h
Zofran 5.7 h 5.7 h
Zoloft 29 h 13 - 45 h
Zolpidem 2.5 h 2 - 3 h
Zonisamide 2.6 days 53 - 75 h
Zopiclone 5 h 4 - 6 h
Zotepine 15 h 14 - 16 h
Zyprexa 37.5 h 21 - 54 h
Zyrtec 7.5 h 6 - 9 h

These values are estimates. The actual half life varies, depending on many user and drug-related variables.

Can the half life of a drug vary?

Yes, the half life of drugs varies depending on 2 large groups of factors:

First, patient-specific variables can affect half life:

  • Gender
  • Age
  • Race or genetics (can influence metabolism)
  • Blood circulation
  • Diet (for example, grapefruit juice)
  • Excessive or low fluid levels
  • History of previous drug use
  • Kidney function (for drugs cleared via the kidneys)
  • Liver function (for drugs metabolized through the liver)
  • Obesity
  • Pre-existing conditions (for example, heart failure)
  • Presence of other drugs
  • Smoking
  • Other variables

And the other set of factors affecting half-life of drug are drug-specific variables:

  • Formulation (for example, extended-release formulations)
  • Behavior in the body (for example, zero-order pharmacokinetics)
  • Administration method (for example, oral)
  • Presence of metabolites or other drugs that may interact
  • Clearance method (for example, via the liver)
  • Place of accumulation (for example, in the fat)
  • If the drug binds to proteins or not
  • Properties (for example, molecule size)
  • The volume of distribution
  • Other variables

Short half life vs long half life

Drugs with short half life act quickly, but their effects wear off faster. They usually must be taken several times per day to achieve the desired result.

Such drugs are harder to withdraw from. That's why drug treatment programs often switch people from drugs with shorter half life to those in the same class with longer one.

Drugs with long half life need longer to start working but their effects last longer. They can be taken daily, weekly, monthly, or even less often! They're usually also milder.

These drugs are more likely to build up in your body over time. It happens if you take the drug more frequently than it's completely gone from your system. The medicine half life calculator helps you decrease the dose over time to keep the same amount of drug present.

What drug has the shortest half life?

As you may have noticed in the above table, adrenaline has one of the shortest half lives of only 2.5 minutes. It clears from the body extremely quickly!

It's used in severe allergic reactions, and its dose sometimes has to be repeated due to the short half life.

What drug has the longest half life?

Amiodarone is the drug with the longest half life among those we collected. It takes up to 107 days for your body to get rid of only half of the dose taken.

It's used in some heart arrhythmias and resuscitation.

What does it mean if a drug has a half-life of 4 hours?

Half life is used to estimate how long does medicine stay in your body. That means half of the drug is gone from your body 4 hours after administration.

Is half life the same as drug duration?

No. Half life is the time it takes half of the drug to be eliminated. Drug duration is the overall time the drug remains in the body.

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