Haldol (Haloperidol) Calculation Question

In our latest question and answer, the pharmacist discusses a calculation question regarding Haldol (haloperidol).

Question

I have an order for Haldol 5 mg/ml. Give 0.5 mg IM q 2 hours prn. How many ml to give?

Asked by JoJo On Jun 06, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Jun 07, 2018

The strength of the Haldol injection is 5 miligrams (mg) per 1 milliliter (mL). If the doctor has instructed you to give or inject 0.5 mg intramuscularly every 2 hours as needed, then you would need to inject 0.1 ml.


Below you can find more information regarding intramuscular (IM) injections and Haldol.


IM Injection

It is important to choose the correct size needle when selecting syringe. The needle need to be long enough to reach the muscle, without leaking to other areas of body.


The recommended gauge of the syringe is between 22 to 25, but the selection for needle length is based upon the muscle mass and age of the patient. Some experts suggest a ⅝-inch needle in the skin is stretch flat, but if the tissue or muscle is bunch and chances of striking bone are low, use a 1-inch needle to make sure the intramuscular injection is successful.


The CDC has listed there recommendations based upon weight here.

Adults (19 or older)Needle Length
Men and Women 130 lbs ( less than 60 kg)1 inch
Men and Women 130-152 lbs (60-70 kg)1 inch
Men 152-260 lbs (70-118 kg)1-1.5 inches
Women 152-200 lbs (70-90 kg)1-1.5 inches
Men over 260 lbs (118kg)1.5 inches
Women over 200 lbs (90 kg)1.5 inches

Inject at 90 degree angle to the deltoid muscle of the arm for adults. Recommendations for children can be found here.


Haldol (haloperidal) is an antipsychotic medication commonly used to treat psychosis, tourette syndrome, and agitation. Do not use Haldol to treat psychosis related to dementia. This medication could cause dizziness and sedation so be careful not to drive while taking Haldol. Also be careful not to stand up too quickly from sitting to prevent from falling.

About the Pharmacist

Dr. Jennifer Oliver Pharm.D

Dr. Jennifer Oliver is a licensed immunizing pharmacist in Florida. She graduated from the University of South Florida with a Doctor of Pharmacy Degree in 2015. Other than her passion for pharmacy, she loves traveling and meeting new people.

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