1. Medication Dosing Abdullah Al.Kattan Pharm.D, MSc.Pharmacology 937 Centre

2. Introduction Every drug has specific doses. And every patient needs a specific drug and specific doses of a drug depending on his health condition, weight and age. In General, there are three types of doses

3. 1- Prophylactic dose: dose that used for prevention from a specific disease. Example: Aspirin 81, 100 or 160 mg used as prophylactic dose in order to prevent stroke and angina pectoris. 2- Therapeutic dose: dose that used for treatment from a specific disease or symptoms. Example: Aspirin 300 and 600 mg used as analgesic and antipyretic treatment of Pain and fever. 3- Toxic dose: dose that are avoided because the dose result in severe adverse effect and can lead to organ failure or even death. Example: Aspirin if taken with higher doses can lead to acute renal failure, acidosis, gastric ulcer, deafness, or nausea and vomiting.

4. Patient Dose Patient dose: it depend on many factors include: -Body weight -Age -Health condition

5. Patient Dose 1-Body weight: almost all medications' doses depend on the body weight of the patient, and it described as mg/kg. Note: some patients are overweight or obese. These patients who have very high WT need to calculate the Ideal body weight (IBW) for overweight patients or the Adjusted body weight (Adj. BW) for obese patients before calculating the dose. IBW = 2.3 × (height in inches – 60) + 50 (for male) IBW = 2.3 × (height in inches – 60) + 45.5 (for female) Remember: (cm) / 2.54 = (inches) Adj. BW = (actual WT – IBW) × 0.4 + IBW

6. What if I don’t know the dose described as (mg/kg) for pediatric..? The adults (16 – 75 years old) dose usually fixed, unless if other factors change the dose. Pediatric dose (AK formula) = Adult dose ÷ 70 (the result of this equation) × child weight = the appropriate dose Patient Dose

7. 2-Age: In general, the body weight is most accurate way to calculate the dose, but the age also could be used to calculate the dose. The adults dose usually fixed, unless if the patient having chronic diseases. Pediatric dose per age is not 100% accurate, but we could depend on age sometimes to calculate OTC medications. Patient Dose Children's dose calculated from adult's dose. Child dose (Dilling's formula) = (Age / 20) × adult dose.

8. Patient Dose Note: Pediatrics age from 1-12 years old have rapid metabolism than adults. So, some drugs’ doses should be slightly higher than usual.

9. Note: newborn's kidney and liver are not fully matured, so some drugs cannot be given until the baby has 2 months old. For example: ceftriaxone and sulfamethoxazole are not given to newborns, because both drugs bound to albumin for long time. So, it will displace bilirubin which already bound to albumin, and results in high bilirubin in the blood (cannot be excreted through the liver without albumin bound, and that condition is called Jaundice). and may results in Kernicterus (high bilirubin in brain) and death. Patient Dose

10. 3-Health condition: a number of serious diseases can affect drug pharmacokinetics and pharmacodynamics, so need dose adjustment. The Elderly patients (> 75 years old), the clearance of drugs reduced because of organs functions reduced by 25-50 %, especially the organs responsible for drugs excretion like kidney and liver. So before calculating the dose of elderly patients, we must see the kidney function test (Creatinine Clearance) and liver function test (AST and ALT). Also, Heart dysfunction will affect all organs including Kidneys and Liver, dose can changed because of: - GIT absorption of medications reduced due to intestinal mucosal edema. - Reduced blood perfusion to the kidneys and liver.

11. Medications Dosing in Ramadan

12. Introduction Most of drugs dosing during Ramadan have no problem with the patients and mostly have no issues. Some drugs that given ≥ 2 times daily may have some concern, and patients should adviced. Healthcare providers should feel easy about it and shouldn’t make it complicated for the patients. And remember, we are here to provide medical informations, and not provide religious informations. We will give recommendations for some of drugs and how Ramadan could affect on drugs’ dose or frequency.

13. Drugs for Diabetes Metformin (750mg controlled release): Given as 2 tablets once daily within or after breakfast or could be taken as one tablet with breakfast and one tablet with sohoor. Metformin (500,850 or 1000mg immediate release): Given as physician direction, and split the doses of metformin through the night time until dawn time. >>Even if the gap between one tablet and the another is only 4 hours. Sulfonylureas 2 nd generation (ex. Gliclazide) or DPP-4 inhibitors (ex. Sitagliptine): Should be taken only once daily before or at the breakfast. SGLT-2 inhibitors (ex. Empagliflozin): Should be taken as usual; one tablet before or at the breakfast. (advice the patient to drink plenty of water due to diuretic effect of SGLT-2 inhibitors).

14. Drugs for Diabetes

15. Example

16. Antibacterial Drugs Antibiotics with short half lives (Amoxicillin, 1 st and 2 nd generation of cephalosporin) should NOT be used as a first line treatment of infections during Ramadan. Reason: Could have high chance of resistance because of reaching lower concentration than MIC. If it used, it should be taken as maximum dose BID.

17. Antibacterial Drugs Antibiotics with long half lives (3 rd generation cephalosporin, macrolides, floroquinolones, tetracyclines, clindamycin, metronidazole and Bactrim) should be used as a first line treatment of infections during Ramadan. Reason: Most of these antibiotics have Post Antibiotic Effect (PAE) and/or mostly concentrations being above MIC. If it used, it should be taken as usual dose OD or BID (depend on the drug).

18. Antiviral Drugs Acyclovir should be shifted to Valacyclovir due to higher bioavailability and long duration of antiviral coverage. Valacyclovir dose is 500-1000mg BID (at breakfast and sohoor meals). Oseltamivir and its active metabolite (oseltamivir carboxylate) have long half life and could be given as 75mg BID (at breakfast and sohoor meals).

19. AntiFungal Drugs Fluconazole, Voriconazole, Posaconazole and itraconazole have long duration of antifungal coverage and their concentrations being above MIC. Levothyroxine Better to be given 2 hours after breakfast during Ramadan.

20. Thank You And Ramadan Kareem