DOSE CALCULATIONS BETTY PHILIP prepared by betty philip

Some common Abbreviations Meaning b.i.d Twice a day Omn.hor Every hour p.o. By mouth p.c. After meals q.s. Quantity sufficient p.r.n As needed

prepared by betty philip q.d. Everyday q.h. Every hour q.i.d Four times a day ss half t.i.d Three times a day prepared by betty philip

Some common conversions 1 gram = 1000mg 1 grain = 60 mg 1 ounce = 30 g 1 fl.oz = 30 ml 1 kg = 2.2 lb

prepared by betty philip Numerical A patient is to be started on 150 mg of a medication and then decreased by 10% of the original dose for each dose until he is receiving 75 mg. When he takes his 75 mg dose, how many total doses will he have taken? prepared by betty philip

Solution: 10% of 150 = 0.10* 150 = 15 150 mg first dose - 15 - 15 135 mg second dose - 15 120 mg third dose 105 mg fourth dose

prepared by betty philip Solution: 105 mg fourth dose - 15 90 mg fifth dose 75 mg sixth dose Total 6 doses prepared by betty philip

Numerical The recommended daily allowance (RDA) of a particular vitamin is 60 mg. If a multivitamin tablet claims to provide 45% of the RDA, how many mg of the particular vitamin would a patient receive from the multivitamin tablet?

prepared by betty philip Solution The multivitamin tablet would give 60 * 45/100 60 * 0.45 = 27mg prepared by betty philip

Numerical A child is taking 12ml of a medication four times per day. If the full bottle contains 16 ounces of the medication, how many days will the bottle last?

prepared by betty philip Solution Per day : 12 * 4 = 48ml Per bottle : 16 * 30ml = 480ml Therefore 480/48 = 10 days prepared by betty philip

Numerical A child who weighs 55lb is to receive 0.05mg of a drug per kg of body weight per dose. How much of the drug should the child receive for each dose?

prepared by betty philip Solution 1 kg = 2.2 lb therefore 55 lb = 55/2.2 = 25 kg 0.05 * 25 = 1.25 mg prepared by betty philip

Numerical Calculate the correct number of tablets or capsules to be administered per dose. The physician writes an order for Diabinese 0.1g p.o. q.d. The container label reads Diabinese 100mg tablets.

prepared by betty philip Solution Order : 0.1g = 0.1 * 1000 = 100mg Supply : 100mg/tab D (desired) * Q =X (amount) H (have) 100/100 * 1 = 1 tab prepared by betty philip

Numerical Lanoxin 0.125 mg p.o. q.d. Supply: Lanoxin 0.25mg tablets Solution: D *Q = 0.125 * 1 = 1/2 tablet H 0.250

prepared by betty philip Numerical Calculate one dose of the drugs ordered Order: Demerol syrup 75mg p.o. q.4h p.r.n. pain Supply: Demerol syrup 50 mg per 5ml prepared by betty philip

Solution IN 5 ml 50 mg ? 75 mg 75 * 5 = 7.5 ml 50

prepared by betty philip Numerical Erythromycin 1.2 g p.o. q.8h Supply: Erythromycin 400mg/5ml Solution IN 5 ml 400 mg ? 1200 mg 1200 * 5 = 15 ml 400 prepared by betty philip

Numerical The physician ordered Keflex 80mg p.o. q.i.d for a child with an upper respiratory infection. The Keflex is supplied in an oral suspension with 250mg per 5ml.

prepared by betty philip Solution IN 5 ml 250 mg ? 80 mg 80 * 5 = 1.6 ml 250 prepared by betty philip

Numerical Order: Ticar 4g IV q.6h for a patient with bacterial septicemia Supply : Ticar 200 mg/ml Recommended adult dosage from package insert: 200-300 mg/kg/day. q. 4-6h Patient weight: 150 lb Calculate how many ml has to be given?

prepared by betty philip Solution 150 lb = 68.2 kg IN 1 ml 200 mg ? 4000 mg 4000 * 1 = 20 ml 200 prepared by betty philip

Numerical Pathocil 125mg p.o. q.6h for a child who weighs 55lb. The recommended dosage of Pathocil for children weighing less than 40kg is 12.5- 25mg/kg/day p.o. in equally divided doses q.6h for moderate to severe infections. Recommended minimum daily dose for this child: Recommended minimum single dose for this child: Recommended maximum daily dose for this child: Recommended maximum single dose for this child:

prepared by betty philip Solution 55 lb = 25 kg Minimum daily dosage : 12.5 mg/kg/day * 25 kg = 312.5 mg/day 312.5/4 = 78.1 mg/ dose Maximum daily dose: 25 mg/kg/day* 25 kg = 625 mg/day 625/4 = 156.3 mg/ dose The dose is safe prepared by betty philip

Numerical Furosemide oral solution 10mg p.o. b.i.d for a child who weighs 16lb. The recommended pediatric dosage is 0.5 – 2 mg/kg b.i.d. Recommended minimum single dose for this child: Recommended maximum single dosage for this child: Is the ordered dosage safe?

prepared by betty philip Solution The weight of the child is 7.3 kg (16/2.2) The minimum single dose for this child is 3.7mg (7.3 * 0.5) The maximum single dose for this child is 14.6mg (7.3 * 2) The dose is safe prepared by betty philip

Numerical How many chloramphenicol capsules, each containing 250 mg, are needed to provide 25 mg per kg per day for 7 days for a person weighing 200lb.

prepared by betty philip 200 lb = 91kg 1 kg ------- 25mg 91 kg ------- 91 * 25 = 2275 mg (for one day) For 7 days 2275 * 7 = 15925 mg I capsule -------- 250 mg ? -------- 15925 64 Capsules prepared by betty philip

Numerical If a vitamin solution contains 0.5 mg of fluoride ion in each milliliter. How many milligrams of fluoride ions would be provided by a dropper that delivers 0.6 ml.

prepared by betty philip Solution 1 ml --------- 0.5 mg 0.6 ml -------- ? 0.5 * 0.6 = 0.3 mg prepared by betty philip

Numerical You receive the following prescription 0.5% eye drops. Instill one drop b.d in both eyes for 5 weeks. How many bottles will u dispense to the patient (15 drops are contained in 1ml).

prepared by betty philip Solution One drop twice a day in both eyes = 4 drops 5 weeks = 35 days (7 * 5) Number of drops for 5 weeks = 35 * 4 = 140 drops I5 drops ----- 1 ml 140 drops ------140/15 = 9.3 ml Therefore dispense 2 Bottles prepared by betty philip

Numerical The usual initial dose of chlorambucil is 150µg/kg of body weight once per day. How many mg should be administered to a patient weighing 154 lb.

prepared by betty philip Solution 1 kg = 2.2 lb ? =154 lb 70 kg The dose now is 0.15mg/kg Therefore 0.15 * 70 = 10.5 mg 1mg = 1000µg ? =150 µg 0.15mg prepared by betty philip

Pediatric calculation A) Proportion to Age a) Young’s Rule b) Dilling’s Rule c) Fried’s Rule d) Cowling’s Rule e) Bastedo’s Rule

prepared by betty philip B) Proportion to Body Weight Clark’s Rule C) Proportion to Surface area Square meter surface area prepared by betty philip

Young’s formula : Age in years * Adult dose Age + 12 Dilling’s Formula: Age in yrs * Adult dose 20

prepared by betty philip Fried’s formula: It is used in infants upto 2 yrs old Age in months * Adult dose 150 Cowling’s rule Age in years +1 * Adult dose 24 prepared by betty philip

Bastedo’s Rule Age in years + 3 30 B. Clarke’s formula Weight(lb) * Adult dose 150

prepared by betty philip C. Proportion to body surface area Body surface area of child * Adult dose Body surface area of adult BSA of adult = 1.73m2 BSA (m2) = height (cm)  weight (kg) 3600 prepared by betty philip

Numerical Bactrim pediatric suspension 7.5 ml p.o. q.12h for a child who weighs 15 kg and has an urinary tract infection. The recommended dosage of Bactrim (trimethoprim and sulfamethoxazole) for such infections in children is based on the trimethoprim at 8 mg/ kg/ day in 2 equal doses. (The label on the container reads 1 teaspoon ful contains 40 mg (trimethoprim) and 200 mg (sulfamethoxazole)) Recommended daily trimethoprim dosage for this child: _________ mg/kg Recommended single trimethoprim dosage for this child: _________ mg/dose Recommended single dose for this child:_________ ml/ dose Is the dose ordered safe ?

prepared by betty philip Solution Recommended daily trimethoprim dosage for this child: 15 *8 = 120 mg/kg Recommended single trimethoprim dosage for this child: 120/2 = 60 mg/dose Recommended single dose for this child: 7.5 ml/dose The dose is safe. prepared by betty philip

Numerical Amoxil oral suspension 100 mg p.o. q.8h for a child who weighs 39 lb (The label on the container reads 20 – 40 mg/kg/day in divided doses every 8 hours) Child’s weight: _________ kg Recommended minimum daily dosage for this child: _________ mg/day Recommended minimum single dosage for this child: _________ mg/dose Recommended maximum daily dosage for this child: _________ mg/day Recommended maximum single dose for this child:_________ mg/ dose Is the dose ordered safe ?

prepared by betty philip Solution Child’s weight:17.7 kg Recommended minimum daily dosage for this child: 20 * 17.7 = 354 mg/day Recommended minimum single dosage for this child: 354/3 = 118 mg/dose Recommended maximum daily dosage for this child: 40 * 17.7 = 708 mg/day Recommended maximum single dose for this child:708/3 = 236 mg/ dose The dose ordered is below the minimum single dose required prepared by betty philip

Numerical Lanoxin 0.15 mg p.o. q.12h for a maintenance dose for a 9 year old child weighs 70 lb. The recomemded maintenance pediatric dosage of lanoxin (digoxin) tablets and elixir is 70 – 10 mcg/kg/day divided and given in 2 to 3 equal doses per day. Child’s weight :_____________ kg

prepared by betty philip Recommended minimum daily dosage for this child: _________ mg/day Recommended minimum single dosage for this child: _________ mg/dose Recommended maximum daily dosage for this child: _________ mg/day Recommended maximum single dose for this child:_________ mg/ dose Is the dose ordered safe ? prepared by betty philip

Solution Child’s weight : 31.8 kg Recommended minimum daily dosage for this child: 31.8 *0.007 =0.22 mg/day Recommended minimum single dosage for this child: 0.22/2 =0.11 mg/dose Recommended maximum daily dosage for this child: 31.8 * 0.007 =0.32 mg/day Recommended maximum single dose for this child: 0.32/2 =0.16 mg/ dose Yes the dose ordered is safe

prepared by betty philip Numerical Gentamicin 40 mg IV q.8h for a premature neonate who is 5 days old and weighs 1800 g. The recommended dosage of gentamicin for children is 2-2.5 mg/kg q.8h; for neonates less than 1 week of age, it is 2.5 mg/kg q.12h Neonate’s weight : ___________ kg Recommended single dose for this neonate : ________ mg/dose Is the ordered dosage safe ? prepared by betty philip

Solution Neonate’s weight :1.8 kg Recommended single dose for this neonate : 1.8 * 2.5 =4.5 mg/dose No the ordered dosage is not safe.

prepared by betty philip Numerical A child weighing 76 lb is ordered to receive 150 mg of clindamycin q 6h. The paediatric drug handbook states the recommended dose is 8-20 mg/kg/day in four divided doses. The Clindamycin is supplied in 100mg scored tablets. How many tablets should you give the patient. prepared by betty philip

prepared by betty philip Solution The weight of the child is 76/2.2 = 34.5 kg By using the formula H/Q = D/X H = Have D = desired Q = Quantity X = Amount prepared by betty philip

prepared by betty philip Solution contd………… 100 = 150 1 X X = 150 = 1.5 tablets 100 prepared by betty philip

Numerical An adult dose of drug is 500mg, what is the dose for a 2-year old child ? (Young’s rule)

prepared by betty philip Solution Age in years * Adult dose Age in years + 12 2 * 500 = 71.4 mg 2+12 prepared by betty philip

Numerical If an adult dose of drug is 750mg, what is the dose for child weighing 20 lbs ?

prepared by betty philip Solution Clark’s Rule = Weight (lb) * Adult Dose 150 20 * 750 = 100 mg prepared by betty philip

Numerical If an adult dose of drug is 100mg, what would be dose for a child that has a body surface area 0.9 m2 ?

prepared by betty philip Solution Body surface area of child * Adult dose Body surface area of adult BSA of adult = 1.73m2 0.9 * 100 1.73 prepared by betty philip

Numerical Vantin 100mg p.o.q.i.d. *10 days for a 4 year old child with tonsillitis who weighs 45 lb. Recommended dosage for children 5 months – 12years: (maximum of 100 mg/dose) q.12h(maximum daily dosage : 200mg) for 5-10 days

prepared by betty philip Numerical contd……… Child’s weight ____________ kg Recommended daily dose for this child: ____________ mg/day The total daily dosage ordered for this infant: __________ mg/day Is the dosage ordered safe? prepared by betty philip

Solution Child’s weight45/2.2 = 20.5 kg Recommended daily dose for this child: 100mg every12hr = 200mg/day The total daily dosage ordered for this infant: 100*4 = 400mg/day The dosage ordered is not safe prepared by betty philip

prepared by betty philip Numerical Rocephin 1 g IV q.12h for a child with a serious infection who weighs 20lb. The recommended pediatric dosage of Rocephin (ceftriaxone sodium) is a total daily dosage of 50-75 mg/kg given once a day (or in equally divided doses twice a day), not to exceed 2g/day. prepared by betty philip

Numerical contd……… Child’s weight: _________ kg Recommended minimum daily dosage for this child: _________ mg/day Recommended minimum single dosage for this child: _________ mg/dose Recommended maximum daily dosage for this child: _________ mg/day Recommended maximum single dose for this child:_________ mg/ dose Is the dose ordered safe ?

prepared by betty philip Solution Child’s weight: 9.1kg Recommended minimum daily dosage for this child: 9.1 * 50 = 455mg/day Recommended minimum single dosage for this child: 455/2 = 227.5mg/dose Recommended maximum daily dosage for this child: 9.1 * 75 = 682.5mg/day Recommended maximum single dose for this child: 682.5/2 = 341.3mg/ dose The dose ordered is not safe prepared by betty philip

Numerical Augmentin 200mg q.12h for a 5- year- old child who weighs 45lb. The recommended dosage of this combination drug is based on the amoxicillin at 25 mg/kg/day in divided doses q.12h or 20 mg/kg/day on divided doses q.8h.

prepared by betty philip Numerical contd……… Child’s weight: _________ kg Recommended daily dosage for this child: _________ mg/day Recommended single dose for this child:_________ mg/ dose Is the dose ordered safe ? prepared by betty philip

Solution Child’s weight: 20.5 kg Recommended daily dosage for this child: 25 *20.5 = 512.5 mg/day Recommended single dose for this child: 512.5/2 = 256.25 mg/ dose The dose ordered is not safe

Numerical (calculate for one dose) Order : Trandate 150mg p.o. bid Supply : Trandate 300 mg tablets

prepared by betty philip Solution D (desired) * Q =X (amount) H (have) 150/300 * 1 = 1/2 tablet prepared by betty philip

Numerical Order: Tranxene 7.5mg p.o. q.i.d is ordered and you have 3.75mg Tranxene capsule available.

prepared by betty philip Solution D (desired) * Q =X (amount) H (have) 7.5/3.75 * 1 = 2 capsules prepared by betty philip

Numerical Order: Oxacillin sodium 0.25g p.o. q.8h Supply : Oxacillin sodium 125 mg/2.5ml

prepared by betty philip Solution D (desired) * Q =X (amount) H (have) 250/125 * 2.5 = 5 ml prepared by betty philip

Numerical Order: Amoxicillin 100mg p.o. q.i.d Supply: 80ml bottle of Amoxil (amoxicillin) oral paediatric suspension 125mg per 5ml

prepared by betty philip Solution D (desired) * Q =X (amount) H (have) 100/125 * 5 = 4 ml prepared by betty philip

Numerical Order: Valproic acid 0.5g p.o. t.i.d Supply : 250mg/5ml in a 16 floz syrup Give : ___________ ml How many full doses are available in the bottle?

prepared by betty philip Solution 250 mg ------- 5 ml 500 mg ------- 500* 5 = 10 ml 250 1 dose = 10 ml ? = 480 ml 480 = 48 doses 10 prepared by betty philip

Numerical Order : Decadron 750 mcg p.o. b.i.d Supply : Decadron 0.75 mg and 1.5mg tablets Select : _________ mg tablets Give : _________ tablets

prepared by betty philip Solution 750 mcg = 0.75 mg Therefore Select : 0.75 mg tablet Give : 1 tablet prepared by betty philip

Numerical Order : Phenobarbital gr ¾ p.o g.d Supply : Phenobarbital 15mg, 30mg, & 60mg Which strength of tablet would you select and how much would you give Select : ____________ mg tablet Give : _____________ tablets

prepared by betty philip Solution gr ¾ = 60 * ¾ = 45 mg Therefore Select : 15mg and 30 mg Give : one of each tablet prepared by betty philip

Numerical Order : Penicillin G potassium 300,000 U IM q.i.d Supply : 500,000 U/ml

prepared by betty philip Solution D (desired) * Q =X (amount) H (have) 300,000/500,000 * 1 = 3/5 ml = 0.6 ml prepared by betty philip

Numerical Order : Tazidine 250 mg IM q.12h Supply : 500 mg vial of powdered Tazidime with 1M reconstitution direction state “For the solution – Add 1.5ml of an approved diluent. Provides an approximate volume of 1.8ml (280 mg/ml)

prepared by betty philip Solution 280 mg in 1 ml 250 mg ? 250 * 1 = 0.89 ml 280 prepared by betty philip

Numerical Bacitracin 750 U I.M. q.8h for an infant who weighs 2500g. The recommended dosage for infants 2.5 kg and below: 900 units/kg/day in 2-3 divided doses; infants over 2.5 kg: 1000 units/kg/day in 2-3 divided doses.

prepared by betty philip Numerical contd………… Child’s weight: _________ kg Recommended daily dosage for this child: _________ U/day Recommended single dose for this child:_________ U/ dose Is the dose ordered safe ? prepared by betty philip

prepared by betty philip Solution Child’s weight: 2.5 kg Recommended daily dosage for this child: 2.5 * 900 = 2250 U/day Recommended single dose for this child:2250/3 = 750 U/ dose Yes the dose ordered is safe prepared by betty philip