Gandhaka Rasayana is a herbal powder or tablet form.
Its Usage:

• It is used to treat chronic fever, skin diseases, diarrhoea, urinary tract disorders, pruritis, malabsorption syndrome, bleeding disorders, oligospermia.
  
• It is anti aging medicine, improves digestion, skin complexion and immunity.

Effect on Tridosha –  Balances Vata, Pitta and Kapha.
Dosage:
1 – 3 grams, once or twice a day before or after food.
Side effect:
Diabetic, hypertensive patients, cardiac patients, obese people, pregnant ladies, lactating mothers and children should take this medicine strictly under medical supervision.
Gandhaka Rasayanam ingredients:
10 g fine powder of Gandhaka – Purified Sulphur
It is ground till dryness for 8 times each with the following.
Go dugdha – Cow milk
Water decoction / juice extract of
Twak – Cinnamon – Cinnamomum zeylanicum
Ela – Cardamom – Elettaria cardamomum
Patra – Cinnamomum tamala
Nagakeshara – Mesua ferrea
Guduchi – Indian Tinospora (stem) – Tinospora cordifolia
Haritaki – Chebulic Myrobalan (fruit rind) – Terminalia chebula
Amalaki -Indian Gooseberry- Emblica officinalis / Phyllanthus emblica
Vibhitaki – Belliric Myrobalan – Terminalia bellirica
Shunti – Ginger (rhizome) – Zingiber officinalis
Bhringaraja – Eclipta alba
Ardraka – Ginger (rhizome) – Zingiber officinalis
Sita – Sugar Syrup
Reference:Yogaratnakara Rasayana Adhikara