**Question:** Drug not given sublingually is:

**Core Concept:** Sublingual administration is a method of drug delivery where medications are placed under the tongue. This allows for rapid absorption of the drug into the bloodstream, bypassing the first-pass effect and reaching the systemic circulation more quickly.

**Why the Correct Answer is Right:**

Drugs administered sublingually are quickly absorbed through the mucous membranes under the tongue, resulting in faster onset of action compared to other routes of administration such as oral, intravenous or intramuscular routes. This is particularly useful for drugs that need to reach the central nervous system (CNS) quickly, like certain antidepressants and anxiolytics.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because drugs given orally are absorbed through the gastrointestinal tract, not the sublingual route. This is a different method and takes longer to reach the CNS.

B. Although administered rectally (rectal), drugs in this option are not specifically mentioned to be administered sublingually, so they are incorrect for this MCQ.

C. Similar to option B, drugs given via the intramuscular route are not administered sublingually and hence are incorrect for this MCQ.

D. Intranasal administration involves the nasal cavity, not the sublingual route. Drugs given intranasally would typically involve the olfactory and respiratory mucosae, not the sublingual mucosa.

**Clinical Pearl:**

The sublingual route is often used for medications that require fast absorption and entry into the CNS. However, the choice of route depends on the pharmacokinetic and pharmacodynamic properties of the drug, as well as the patient's condition and response to treatment.

**Correct Answer:** Intranasal (D)

**Core Concept:** Intranasal administration involves the nasal cavity, allowing drugs to enter the systemic circulation through the mucosal lining and then travel via the systemic circulation to the brain. This route is often used for medications like local anesthetics, antihistamines, and certain analgesics.

**Why Each Wrong Option is Incorrect:**

A. Oral medications are absorbed through the gastrointestinal tract and not the sublingual route.
B. Intramuscular injections are administered into muscle tissue, not sublingually, making them incorrect for this MCQ.
C. Intranasal medications enter the systemic circulation through the nasal cavity, bypassing the sublingual route.

**Clinical Pearl:**

The choice of administration route depends on the pharmacological properties of the drug and the patient's condition. Oral, intramuscular, and intravenous routes are more common for systemic administration, while sublingual, intranasal, and transdermal routes are suitable for drugs needing rapid entry into the systemic circulation (e.g., local anesthetics, antihistamines, and analgesics).

**Correct Answer:** Intranasal (D)