Question

The doctor orders phenobarbital 15 mg bid po. You have available phenobarbital 60 mg powder which says to add 5.7 ml of sterile water to yield a total of 6 ml of solution. The child weighs 110 pounds. The Pediatric Reference states to give 0.4 mg/kg/24 hr. Pt weighs Kg. Total mg in 24 hrs ordered Total mg/24 safe dose. Maximum safe to give every 12 hours_ Amount you would administer ml. (IMD order not safe, calculate based on maximum safe dosage)

Answer 1

ANSWER.

4) Calculation of weight(kg) of the patient.

       Weight of the patient = 110 pounds

     Convert pound to kg

               1 pound = 0.454 kg

      So

       Weight of the patient in kg = 110 * 0.454

                                                  = 49.9 kg.

* Total mg in 24 hrs ordered = 15 mg bid or twice a day for 24 hr

                                              = 15 * 2

                                              = 30 mg /24hr

* Total mg/24 hr safe dose.

            Safe dose as per reference = 0.4 mg/kg/24hr.

            Weight of the patient = 49.9 kg.

     Safe dose for this patient = 0.4 * 49.9

                                               = 19.96 mg/24hr.

* Maximum safe dose to give every 12 hr.

        safe dose for 24 hr = 19.96 mg/24 hr

        safe dose for 12 hr = X mg

                       24 = 19.96

                       12 = X

                  24X = 19.96 * 12

                     24X = 239.5

                         X = 239.5 / 24

                            = 9.9 mg/12hr.

*Ordered dose = 15 mg/12 hr (15 mg bid) is not safe for this patient.

* Calculation of amount administer per ml.

        Formula

            Volume(ml) = Desired dose/Dose in hand * Quantity

     Here

        Ordered dose is not safe for this patient so maximum safe dose is used

        as desired dose.

         Desired dose (D) = 9.9 mg bid

         Dose in hand (H) = 60 mg

             Quantity (Q) = 6 ml

   As per above formula

           Volume(ml) of drug required = D/H *Q

                                                         = 9.9/60 * 6

                                                         = 0.17 * 6

                                                         = 1 ml bid PO.