There is nothing wrong with you telling a patient about medicine that is appropriate for him, so long as you adhere to the following guidelines:
1- It should be based on knowledge of the medicine and how suitable it is for the patient.
2- That should have to do with minor, ordinary matters such as headaches, colds and so on, that do not require any examinations or tests.
3- That should not be done with the aim of promoting sales of a particular medicine when there are other medicines that are more beneficial for the patient in terms of efficacy or cost.
If these guidelines are followed, this action comes under the heading of being kind to people and sparing them the cost of medical consultation.
With regard to the doctor's liability, the basic principle concerning that is the hadeeth narrated by Amr ibn Shuayb, from his father, from his grandfather who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: Whoever practices medicine although he is not known for that will be held liable.
Narrated by Abu Dawood, 4586; an-Nasaa'i, 4830; Ibn Maajah, 3466. There are some reservations about its isnaad, but it was classed as hasan by al-Albaani in Sunan Abi Dawood.
Cases in which a doctor is held liable have been discussed in the answer to question no. 114047.
We ask Allah to help and guide us and you.
And Allah knows best.
Reproduced from Islam QA