We received following prescription: Cysteine 30mg/5ml methionine 30mg/5ml biotin 2mg/5ml in Sirupus simplex ad 300 cc

I suppose "it" beats biotin seen cysteine and methionine are soluble in water. The solubility of biotin in water is 22 mg/100 ml and you have 40mg/100ml. Now biotin is also noticeably better soluble in warm water and could also be better soluble in Sirupus simplex. Therefore, I would start to warm up most of the sugar syrup to 80 à 90 ° C and see if the biotin dissolves and remains dissolved after cooling. If not then I would add 20 mg NaHCO3. These should bring the Biotin into solution! After that, cysteine and methionine are dissolved. Store in a well-closed brown red bottle.